Patent Application
20060214842
1. Field of the Invention
The present invention relates to a mixer for use in a millimeter-wave integrated circuit, a millimeter-wave radar module, or the like, and more particularly to a mixer in which a bias supply circuit of a high-frequency detection element as a component of the mixer is provided with a pre-set variable resistor thereby to keep characteristics such as mixing characteristics and transmission characteristics of the mixer tuned satisfactorily, and to a high-frequency transmitting/receiving apparatus having the mixer.
The present invention also relates to a radar apparatus having the high-frequency transmitting/receiving apparatus, and a vehicle equipped with the radar apparatus.
2. Description of the Related Art
Some examples of mixers of conventional design have hitherto been known, such as those which have been disclosed in Japanese Unexamined Patent Publications JP-A 10-242766 (1998), JP-A2001-203537, JP-A2002-158540, and JP-A 2002-290113. Among them, disclosed in JP-A 10-242766 is a mixer that employs NonRadiative Dielectric Waveguide (hereafter also referred to simply as “an NRD guide”). In the mixer, at the end of a dielectric strip line are disposed a Schottky-barrier diode acting as a high-frequency detection element and a substrate for supplying a bias to the Schottky-barrier diode. Moreover, a cavity resonator is arranged by way of a direction changer for changing the direction of a magnetic line of force by 90°. Inserted into the cavity resonator is a movable part for varying a resonant frequency. By moving the movable part, the resonant frequency of the cavity resonator is caused to vary, whereby a change can be achieved in an impedance when the Schottky-barrier diode is viewed as from the dielectric strip line.
Moreover, there have been proposed high-frequency transmitting/receiving apparatuses designed to operate in combination with such a mixer, which are expected to find applications in a millimeter-wave radar module, a millimeter-wave wireless radio communications apparatus, or the like. For example, such a high-frequency transmitting/receiving apparatus is disclosed in Japanese Unexamined Patent Publication JP-A 2000-258525. The high-frequency transmitting/receiving apparatus disclosed in JP-A 2000-258525 is of the type that adopts a pulse modulation scheme.
It has been known that, in such a conventional high-frequency transmitting/receiving apparatus, a nonradiative dielectric line is suitable for use as a high-frequency transmission line for providing connection among the high-frequency circuit elements and transmitting high-frequency signals.
Conventionally, a metal waveguide has commonly been used as means for transmitting micro or millimeter waves. However, in keeping up with the recent demand for a down-sized high-frequency module, development has been under way to come up with a high-frequency module that employs a dielectric strip line as a waveguide for transmitting high-frequency signals. Against this backdrop, the nonradiative dielectric line has attracted much attention as a new high-frequency transmission line because of its ability to transmit high-frequency signals with low loss.
Moreover, examples of a conventional radar apparatus having the high-frequency transmitting/receiving apparatus and a vehicle equipped with the radar apparatus are disclosed in Japanese Unexamined Patent Publication JP-A 2003-35768, for example.
However, conventional constructions have the following disadvantages. In such a mixer as disclosed in JP-A 10-242766, an adjustment mechanism (corresponding to the cavity resonator and the movable part, as exemplified) for adjusting mixing characteristics and the transmission characteristics of the mixer is so formed as to extend from the high-frequency detection element arranged at the end of the high-frequency transmission line. By adjusting its structural dimension, the electrical length of the adjustment mechanism through which high-frequency signals are transmitted is caused to vary, so that a change may be achieved in the impedance at the end of the adjustment mechanism. In this case, however, there is a risk of the electrical length being varied in the presence of only slight play in the structure. This gives rise to a problem of poor controllability. In an attempt to overcome the problem, removing the play nearly perfectly leads to an impractical scale-up of the adjustment mechanism as a whole.
Furthermore, occurrence of oscillation or thermal expansion and contraction causes deviation in the electrical length of the adjustment mechanism such as the cavity resonator and the movable part. Thus, although the electrical length is adjusted optimally in advance, it may be deviated easily. This gives rise to a problem of poor stability.
In addition, in the conventional high-frequency transmitting/receiving apparatus having such a mixer, because of tuning inaccuracy or instability in the mixer, it is impossible to ensure a uniform reception sensitivity. This gives rise to a problem of difficulty in attaining excellent characteristics with stability.
On the other hand, in the high-frequency transmitting/receiving apparatus disclosed in JP-A 2000-258525, as shown in the schematic block circuit diagram depicted in
Moreover, in the radar apparatus employing such a high-frequency transmitting/receiving apparatus, a low-intensity high-frequency signal reflected from a far-off object to be detected is buried in a high-frequency signal transmitted when the modulator 63 is kept in an OFF state, namely, noise. This leads to narrowness in detectable range and susceptibility to erroneous detection, which give rise to a problem of a delay in detecting an object to be detected.
Further, in the vehicle or small boat equipped with such a radar apparatus, a to-be-detected object is detected by the radar apparatus. In response to the detected information, the vehicle or small boat takes proper action such as collision avoidance and braking. However, because of the delay of target detection, an abrupt action is caused in the vehicle or small boat after the detection operation.
The invention has been devised in view of the above-described problems of which improvement is desired with the conventional art, and accordingly one object of the invention is to provide a mixer in which a bias supply circuit of a high-frequency detection element for constituting the mixer is provided with a pre-set variable resistor thereby to keep characteristics such as mixing characteristics and transmission characteristics of the mixer tuned satisfactorily, and also provide a high-frequency transmitting/receiving apparatus having the mixer that is remarkable for constructional simplicity and performance, and is capable of offering excellent reception performance, with high transmission power ON/OFF ratio, by preventing part of a high-frequency signal intended for transmission from being transmitted as an unwanted signal when a modulator is kept in an OFF state.
Another object of the invention is to provide a radar apparatus having the high-performance high-frequency transmitting/receiving apparatus, and a vehicle equipped with the radar apparatus.
The invention provides a mixer comprising:
a coupler having two input ends and one or two output ends;
a high-frequency detection element disposed at the output end of the coupler; and
a bias supply circuit connected to the high-frequency detection element, for supplying a bias current to the high-frequency detection element; wherein the high-frequency detection element is provided with a pre-set variable resistor for controlling the bias current which passes through the high-frequency detection element.
According to the invention, in the mixer, the coupler includes two input ends and one or two output ends. At the output end of the coupler is disposed the high-frequency detection element. Connected to the high-frequency detection element is the bias supply circuit having the pre-set variable resistor for controlling a bias current which passes through the high-frequency detection element. In this construction, by virtue of the pre-set variable resistor, in accordance with the property of the high-frequency detection element, such as characteristics of noise generated by a resistance component of the high-frequency detection element, and the manner of mounting the high-frequency detection element, a bias current can be set at an appropriate value at the time of adjusting characteristics such as mixing characteristics and the transmission characteristics of the mixer, and, at all other times, the bias current can be maintained at the preset value with stability in spite of the presence of a slight mechanical play, as compared with a case of exercising electrical length control. Thus, in contrast to the case of exercising electrical length control, even if a mechanical play exists, it is possible to stabilize the working condition after the setting. As a result, characteristics such as mixing characteristics and the transmission characteristics of the mixer can be tuned with high accuracy and stability.
In the invention, it is preferable that a trimmable chip resistor is employed as the pre-set variable resistor of the mixer.
According to the invention, in the mixer, a trimmable chip resistor is preferably employed as the pre-set variable resistor. In the absence of a movable part, the trimmable chip resistor is able to act to maintain a determined resistance without fail in spite of occurrence of an external force such as vibration. As a result, the aforementioned characteristics can be tuned with higher stability.
The invention provides a high-frequency transmitting/receiving apparatus comprising:
a high-frequency oscillator for generating a high-frequency signal;
a branching device having two output portions, connected to the high-frequency oscillator, for branching the high-frequency signal given by the high-frequency oscillator and outputting the branched high-frequency signal components from one and the other of the two output portions, respectively;
a modulator connected to the one output portion of the branching device, for modulating the branched high-frequency signal component and outputting a high-frequency signal intended for transmission;
a signal separating device having a first terminal, a second terminal, and a third terminal, for receiving at the first terminal the high-frequency signal intended for transmission from the modulator, for outputting from the second terminal the high-frequency signal intended for transmission inputted from the first terminal, and for outputting from the third terminal a high-frequency signal inputted from the second terminal;
a transmitting/receiving antenna connected to the second terminal; and
any one of the mixers mentioned above having, among the two input ends, one input end connected to the other output portion, and the other input end connected to the third terminal, for mixing the branched high-frequency signal component outputted from the other output portion and a high-frequency signal received by the transmitting/receiving antenna and generating an intermediate-frequency signal.
According to the invention, the high-frequency signal oscillated by the high-frequency oscillator is given to the branching device so as to be branched at the branching device, and the branched high-frequency signal components may be outputted from one output portion and the other output portion of the branching device. The high-frequency signal outputted from the one output portion is given to the modulator so as to be given to the first terminal of the signal separating device as a high-frequency signal intended for transmission. The signal separating device outputs the high-frequency signal intended for transmission given to the first terminal from the second terminal. The high-frequency signal intended for transmission is radiated as an electric wave from the transmitting/receiving antenna connected to the second terminal. A high-frequency signal received by the transmitting/receiving antenna is given to the second terminal, and the signal separating device outputs the high-frequency signal given to the second terminal from the third terminal. The signal separating device can separate the high-frequency signal intended for transmission given to the transmitting/receiving antenna and the high-frequency signal received by the transmitting/receiving antenna. The high-frequency signal outputted from the third terminal is given to the other input end of the mixer. At the same time, a local high-frequency signal is given from the other output portion of the branching device to one input end of the mixer, whereby the mixer mixes the high-frequency signal received by the transmitting/receiving antenna and the local high-frequency signal and generates an intermediate-frequency signal. In this high-frequency transmitting/receiving apparatus, one of the mixers of the invention is provided and therefore, by virtue: of the mixer, the mixing characteristics and the transmission characteristics of the mixer can be tuned appropriately in accordance with the property of the high-frequency detection element and the manner of mounting the high-frequency detection element. This makes it possible to realize a high-performance high-frequency transmitting/receiving apparatus that offers excellent reception sensitivity with stability.
In the invention, it is preferable that, in the high-frequency transmitting/receiving apparatus, a transmission coefficient between the two input ends of the mixer is determined in such a way that the following expression holds: Pa2=Pb2, under the conditions that a high-frequency signal passing through the modulator placed in an OFF state is defined as Wa2; a high-frequency signal that has been transmitted from the other output portion of the branching device to the output portion of the modulator by way of the mixer and the signal separating device, and then reflected from the output end of the output portion of the modulator is defined as Wb2; an intensity of the high-frequency signal Wa2 is represented by Pa2; and an intensity of the high-frequency signal Wb2 is represented by Pb2.
According to the invention, in the high-frequency transmitting/receiving apparatus, a transmission coefficient between the two input ends of the mixer is determined in such a way that the following expression holds: Pa2=Pb2, under the conditions that a high-frequency signal passing through the modulator placed in an OFF state is defined as Wa2; a high-frequency signal that has been transmitted from the other output portion of the branching device to the output portion of the modulator by way of the mixer and the signal separating device, and then reflected from the output end of the output portion of the modulator is defined as Wb2; the intensity of the high-frequency signal Wa2 is represented by Pa2; and the intensity of the high-frequency signal Wb2 is represented by Pb2. In this case, since the transmission coefficient between the input ends of the mixer can be adjusted properly through tuning of the mixer, it is possible to substantially equate the intensity Pa2 of the high-frequency signal passing through the modulator placed in an OFF state with the intensity Pb2 of the high-frequency signal reflected from the output end of the modulator after passing through the mixer side and the signal separating device. Therefore, these high-frequency signals interfere with each other effectively thereby to cause attenuation. This makes it possible to realize a high-performance high-frequency transmitting/receiving apparatus in which its transmission/reception capability can be enhanced by preventing part of a high-frequency signal intended for transmission from being transmitted as an unwanted signal when the modulator is kept in an OFF state.
In the invention, it is preferable that a distance (line length) between one output end of the output portion of the branching device and the modulator, or a distance (line length) between the other output end of the output portion of the branching device and the modulator, with the mixer and the signal separating device lying therebetween, is determined in such a way that the following expression holds: δ=(2N+1)·π (N represents an integer), where δ represents the difference in phase between the high-frequency signals Wa2 and Wb2 at a center frequency.
According to the invention, in the high-frequency transmitting/receiving apparatus, the distance (line length) between one output end of the output portion of the branching device and the modulator, or the distance (line length) between the other output end of the output portion of the branching device and the modulator, with the mixer and the signal separating device lying therebetween, is determined in such a way that the following expression holds: δ=(2N+1)·π (N represents an integer), where δ represents the difference in phase between the high-frequency signals Wa2 and Wb2 at a center frequency. In this case, in the region between the output end of the modulator and the signal separating device, the high-frequency signals Wa2 and Wb2 are synthesized in phase opposition and cancel out each other thereby to cause attenuation most effectively. This makes it possible to realize a high-performance high-frequency transmitting/receiving apparatus in which its transmission/reception capability can be enhanced by preventing, in a more effective manner, part of a high-frequency signal intended for transmission from being transmitted as an unwanted signal when the modulator is kept in an OFF state.
The invention provides a high-frequency transmitting/receiving apparatus comprising:
a high-frequency oscillator for generating a high-frequency signal;
a branching device connected to the high-frequency oscillator, for branching the high-frequency signal given by the high-frequency oscillator so that the branched high-frequency signal components may be outputted from one output portion and the other output portion thereof, respectively;
a modulator connected to the one output portion of the branching device, for modulating the high-frequency signal component branched at the one output portion and outputting a high-frequency signal intended for transmission;
an isolator having an input terminal and an output terminal, for outputting the high-frequency signal intended for transmission from the output terminal thereof when the high-frequency signal intended for transmission is given from the modulator to the input terminal thereof;
a transmitting antenna connected to the output terminal;
a receiving antenna; and
one of the mixers mentioned above having, among the two input ends, one input end connected to the other output portion of the branching device and the other input end connected to the receiving antenna, for mixing the branched high-frequency signal component outputted from the other output portion and a high-frequency signal received by the receiving antenna and generating an intermediate-frequency signal.
According to the invention, the high-frequency signal oscillated from the high-frequency oscillator is given to the branching device so as to be branched at the branching device, and the branched high-frequency signal components may be outputted from one output portion and the other output portion of the branching device. The high-frequency signal outputted from the one output portion is given to the modulator so as to be given to the input terminal of the isolator as a high-frequency signal intended for transmission. The isolator passes the high-frequency signal intended for transmission given to the input terminal so as to output the high-frequency signal intended for transmission from the output terminal. The high-frequency signal intended for transmission is radiated as an electric wave from the transmitting antenna connected to the output terminal. A high-frequency signal received by the receiving antenna is given to the other input end of the mixer. At the same time, a local high-frequency signal is given from the other output portion of the branching device to the one input end of the mixer, whereby the mixer mixes the high-frequency signal received by the receiving antenna and the local high-frequency signal and generates an intermediate-frequency signal. In this high-frequency transmitting/receiving apparatus, one of the mixers of the invention is provided and therefore, by virtue of the mixer, mixing characteristics and the transmission characteristics of the mixer can be tuned appropriately in accordance with the property of the high-frequency detection element and the manner of mounting the high-frequency detection element. This makes it possible to realize a high-performance high-frequency transmitting/receiving apparatus that offers excellent reception sensitivity with stability.
The invention provides a high-frequency transmitting/receiving apparatus comprising:
a high-frequency oscillator for generating a high-frequency signal;
a switching device having two output portions, connected to the high-frequency oscillator, for selectively outputting the high-frequency signal given by the high-frequency oscillator from one or both of the output portions thereof;
a signal separating device having a first terminal, a second terminal, and a third terminal, for receiving at the first terminal a high-frequency signal intended for transmission from the one output portion of the switching device, for outputting from the second terminal the high-frequency signal intended for transmission inputted from the first terminal, and for outputting from the third terminal a high-frequency signal inputted from the second terminal;
a transmitting/receiving antenna connected to the second terminal; and
one of the mixers mentioned above having, among the two input ends, one input end connected to the other output portion and the other input end connected to the third terminal, for mixing the high-frequency signal outputted from the other output portion and a high-frequency signal received by the transmitting/receiving antenna so as to generate an intermediate-frequency signal.
According to the invention, the high-frequency signal oscillated from the high-frequency oscillator is given to the switching device. The switching device selectively outputs the high-frequency signal given from the high-frequency oscillator from the one or both of the output portions thereof. The high-frequency signal outputted from the one output portion is given to the first terminal of the signal separating device as a high-frequency signal intended for transmission. The signal separating device outputs the high-frequency signal intended for transmission given to the first terminal from the second terminal. The high-frequency signal intended for transmission is radiated as an electric wave from the transmitting/receiving antenna connected to the second terminal. A high-frequency signal received by the transmitting/receiving antenna is given to the second terminal. The signal separating device outputs the high-frequency signal given to the second terminal from the third terminal. The signal separating device can separate the high-frequency signal intended for transmission given to the transmitting/receiving antenna and the high-frequency signal received by the transmitting/receiving antenna. The high-frequency signal outputted from the third terminal is given to the other input end of the mixer. At the same time, the high-frequency signal outputted from the other output portion of the switching device is given to the one input end of the mixer as a local high-frequency signal. The mixer mixes the high-frequency signal received by the transmitting/receiving antenna and the local high-frequency signal and generates an intermediate-frequency signal. In this high-frequency transmitting/receiving apparatus, one of the mixers of the invention is provided and therefore, by virtue of the mixer, mixing characteristics and the transmission characteristics of the mixer can be tuned appropriately in accordance with the property of the high-frequency detection element and the manner of mounting the high-frequency detection element. This makes it possible to realize a high-performance high-frequency transmitting/receiving apparatus that offers excellent reception sensitivity with stability.
The invention provides a high-frequency transmitting/receiving apparatus comprising:
a high-frequency oscillator for generating a high-frequency signal;
a switching device having two output portions, connected to the high-frequency oscillator, for selectively outputting the high-frequency signal given by the high-frequency oscillator from one or both of the output portions thereof;
a transmitting antenna connected to the one output portion of the switching device;
a receiving antenna; and
one of the mixers mentioned above having, among the two input ends, one input end connected to the other output portion of the switching device and the other input end connected to the receiving antenna, for mixing the high-frequency signal outputted from the other output portion of the switching device and a high-frequency signal received by the receiving antenna so as to generate an intermediate-frequency signal.
According to the invention, the high-frequency signal oscillated from the high-frequency oscillator is given to the switching device. The switching device selectively outputs the high-frequency signal given from the high-frequency oscillator from the one or both of the output portions thereof. The high-frequency signal outputted from the one output portion is given to the transmitting antenna as a high-frequency signal intended for transmission so as to be radiated as an electric wave from the transmitting antenna. A high-frequency signal received by the receiving antenna is given to the mixer. At the same time, the high-frequency signal outputted from the other output portion of the switching device is given as a local high-frequency signal, whereby the mixer mixes the high-frequency signal received by the receiving antenna and the local high-frequency signal and generates an intermediate-frequency signal. In this high-frequency transmitting/receiving apparatus in which an antenna for transmission and an antenna for reception are provided separately, one of the mixers of the invention is provided and therefore, also in a high-frequency transmitting/receiving apparatus in which an antenna for transmission and an antenna for reception are provided separately, by virtue of the mixer, mixing characteristics and the transmission characteristics of the mixer can be tuned appropriately in accordance with the property of the high-frequency detection element and the manner of mounting the high-frequency detection element. This makes it possible to realize a high-performance high-frequency transmitting/receiving apparatus that offers excellent reception sensitivity with stability.
The invention provides a high-frequency transmitting/receiving apparatus comprising:
a high-frequency oscillator for generating a high-frequency signal;
a branching device having two output portions, connected to the high-frequency oscillator, for branching the high-frequency signal given by the high-frequency oscillator and outputting the branched high-frequency signal components from one and the other of the two output portions, respectively;
a signal separating device having a first terminal, a second terminal, and a third terminal, for receiving at the first terminal the high-frequency signal intended for transmission from the one output portion of the branching device, for outputting from the second terminal the high-frequency signal intended for transmission inputted from the first terminal, and for outputting from the third terminal the high-frequency signal inputted from the second terminal;
a transmitting/receiving antenna connected to the second terminal; and
any one of the mixers mentioned above having, among the two input ends, one input end connected to the other output portion, and the other input end connected to the third terminal, for mixing the branched high-frequency signal component outputted from the other output portion and a high-frequency signal received by the transmitting/receiving antenna and generating an intermediate-frequency signal.
According to the invention, the high-frequency signals oscillated by the high-frequency oscillator is given to the branching device so as to be branched at the branching device, and the branched high-frequency signal components may be outputted from one output portion and the other output portion of the branching device. The high-frequency signal outputted from the one output portion is given to the first terminal of the signal separating device as a high-frequency signal intended for transmission. The signal separating device outputs the high-frequency signal intended for transmission given to the first terminal from the second terminal. The high-frequency signal intended for transmission is radiated as an electric wave from the transmitting/receiving antenna connected to the second terminal. A high-frequency signal received by the transmitting/receiving antenna is given to the second terminal, and the signal separating device outputs the high-frequency signal given to the second terminal from the third terminal. The signal separating device can separate the high-frequency signal intended for transmission given to the transmitting/receiving antenna and the high-frequency signal received by the transmitting/receiving antenna. The high-frequency signal outputted from the third terminal is given to the other input end of the mixer. At the same time, a local high-frequency signal is given from the other output portion of the branching device to one input end of the mixer, whereby the mixer mixes the high-frequency signal received by the transmitting/receiving antenna and the local high-frequency signal and generates an intermediate-frequency signal. In this high-frequency transmitting/receiving apparatus, one of the mixers of the invention is provided and therefore, by virtue of the mixer, the mixing characteristics and the transmission characteristics of the mixer can be tuned appropriately in accordance with the property of the high-frequency detection element and the manner of mounting the high-frequency detection element. This makes it possible to realize a high-performance high-frequency transmitting/receiving apparatus that offers excellent reception sensitivity with stability.
The invention provides a high-frequency transmitting/receiving apparatus comprising:
a high-frequency oscillator for generating a high-frequency signal;
a branching device connected to the high-frequency oscillator, for branching the high-frequency signal given by the high-frequency oscillator so that the branched high-frequency signal components may be outputted from one output portion and the other output portion thereof, respectively;
a transmitting antenna connected to the one output portion;
a receiving antenna; and
one of the mixers mentioned above having, among the two input ends, one input end connected to the other output portion of the branching device and the other input end connected to the receiving antenna, for mixing the branched high-frequency signal component outputted from the other output portion and a high-frequency signal received by the receiving antenna and generating an intermediate-frequency signal.
According to the invention, the high-frequency signal oscillated from the high-frequency oscillator is given to the branching device so as to be branched at the branching device, and the branched high-frequency signal components may be outputted from one output portion and the other output portion of the branching device. The high-frequency signal outputted from the one output portion is given to the transmission antenna as a high-frequency signal intended for transmission. The high-frequency signal intended for transmission is radiated as an electric wave from the transmitting antenna connected to the one output portion of the branching device. A high-frequency signal received by the receiving antenna is given to the other input end of the mixer. At the same time, a local high-frequency signal is given from the other output portion of the branching device to the one input end of the mixer, whereby the mixer mixes the high-frequency signal received by the receiving antenna and the local high-frequency signal and generates an intermediate-frequency signal. In this high-frequency transmitting/receiving apparatus, one of the mixers of the invention is provided and therefore, by virtue of the mixer, mixing characteristics and the transmission characteristics of the mixer can be tuned appropriately in accordance with the property of the high-frequency detection element and the manner of mounting the high-frequency detection element. This makes it possible to realize a high-performance high-frequency transmitting/receiving apparatus that offers excellent reception sensitivity with stability.
The invention provides a radar apparatus comprising:
one of the high-frequency transmitting/receiving apparatuses mentioned above; and
a distance information detector for detecting data on a distance to an object to be detected by processing the intermediate-frequency signal outputted from the high-frequency transmitting/receiving apparatus.
According to the invention, the radar apparatus is composed of: one of the high-frequency transmitting/receiving apparatuses described above; and the distance information detector for detecting data on a distance to an object to be detected by processing the intermediate-frequency signal outputted from the high-frequency transmitting/receiving apparatus. In this construction, the high-frequency transmitting/receiving apparatus of the invention included therein allows transmission of satisfactory high-frequency signals with high transmission power ON/OFF ratio and allows reception with excellent reception sensitivity. Thus, not only is it possible to detect an object to be detected swiftly without fail, but it is also possible to detect both nearby and far-off target objects successfully without fail.
The invention provides a radar-bearing vehicle comprising the radar apparatus mentioned above, which is used to detect an object to be detected.
According to the invention, the radar-bearing vehicle includes the radar apparatus mentioned above which is used to detect an object to be detected. Since the radar apparatus acts to detect swiftly an object to be detected, for instance, other vehicles or an obstruction on the road without fail, it is possible to exercise proper control of the vehicle and to give a driver a warning appropriately without causing abrupt actions in the vehicle to avoid collision.
Other and further objects, features, and advantages of the invention will be more explicit from the following detailed description taken with reference to the drawings wherein:
Now referring to the drawings, preferred embodiments of the invention are described below.
At the outset, a mixer and a high-frequency transmitting/receiving apparatus having the mixer embodying the invention will be described in detail with reference to the accompanying drawings.
In
Further, in
In the mixer 6 according to one embodiment of the invention, as shown in the circuit diagram depicted in
As described in more detail, the output end 1C of the coupler 1 is connected to an anode of the Schottky-barrier diode 2, and a cathode of the Schottky-barrier diode 2 is grounded. The bias supply circuit C is connected to an anode of the Schottky-barrier diode 2.
On the other hand, in the mixer 16 according to another embodiment of the invention, as shown in
Moreover, in the constructions thus far described, as shown in the circuit diagram depicted in
As shown in
The trimmable chip resistor 3 covers the resistor layer 3b between the electrodes 3c1 and 3c2, and may have a protective film having electrical isolation. The protective film passes around 99% of a light of the YAG laser therethrough. By providing such a protective film, it is unnecessary to separately perform a process for protecting the resistor layer 3b after trimming. This facilitates an aftertreatment. Moreover, the resistor layer 3b is protected by the protective film. Consequently, the resistance is prevented from being varied so that a stable resistance is maintained in the trimmable chip resistor 3.
According to the mixers 6, 16 embodying the invention as shown in FIGS. 1 to 4, just like the mixer of conventional design, high-frequency signals inputted from the two input ends 1a and 1b (26a and 27a) are mixed together (mixing) so as to generate an intermediate-frequency signal. In general, mixing characteristics, as well as the transmission characteristics of the mixer, are dependent upon a bias current passing through the Schottky-barrier diode 2 (45). In light of this, in the invention, the trimmable chip resistor 3 is arranged between the direct current voltage source 5 and the Schottky-barrier diode 2 (45), as a pre-set variable resistor for controlling the bias current. By adjusting the resistance of the trimmable chip resistor 3 properly through trimming or the like technique, it is possible to control the bias current so as to keep the mixing characteristics and the transmission characteristics of the mixer tuned optimally (tuning).
Note that, in the invention, the mixing characteristics refer mainly to conversion gain characteristics defined by the relative intensity ratio between high-frequency signals subjected to mixing and an intermediate-frequency signal to be outputted. On the other hand, the transmission characteristics of the mixer refer to the transmission characteristics of high-frequency signals passing through the two input ends of the mixer.
Instead of the trimmable chip resistor 3 such as shown herein, it is also possible to use another type of pre-set variable resistor, for example, a mechanical trimmer resistor or potentiometer such as a rotary-type or contact-type potentiometer. In either case, substantially the same effect can be achieved. However, the use of the trimmable chip resistor 3 is desirable in that no resistance drift takes place in spite of occurrence of external vibration, and that it offers high reliability against temperature and moisture variation.
Specifically, the trimmable chip resistor 3 is designed as follows. As shown in
When the resistance of the trimmable chip resistor 3 is adjusted, the initial value of the resistance is generally set to be relatively small in advance within a desired adjustment range, so that the resistance may be adjusted to increase gradually. Moreover, before increasing the area of the trimming portion 3d by proceeding linear cutting, the width of the trimming portion 3d is set at a predetermined value in correspondence with the spot size of the YAG laser light. Then, as the YAG laser light is allowed to scan in one axial direction, the area of the trimming portion 3d is increased correspondingly in the scanning direction. By applying the YAG laser light repeatedly to the same part under pulsed operation prior to a subsequent scanning, it is possible to exercise resistance control (trimming) with high accuracy.
In the embodiment, a part of the resistor layer 3b is oxidized, thereby varying the resistance of the resistor layer 3b. However, in another embodiment of the invention, a part of the resistor layer 3b may be cut away by a laser, thereby varying the resistance of the resistor layer 3b.
The trimming portion 3d is not limited to the linear oxidized portion as shown in
An extending direction of the first oxidized portion 3d1 and an extending direction of the second oxidized portion 3d2 are in parallel. The first oxidized portion 3d1 and the second oxidized portion 3d2 are formed so as not to be connected to each other. It is desirable that an end of the first oxidized portion 3d1 on the second oxidized portion 3d2 side and an end of the second oxidized portion 3d2 on the first oxidized portion 3d1 side are formed away at a predetermined distance, in a direction perpendicular to the extending direction of the first oxidized portion 3d1 and second oxidized portion 3d2 and an thickness direction of the resistor layer 2b, that is the longitudinal direction X1 of the resistor layer 2b.
In the example shown in
Moreover, as shown in
In this case, a stress placed on the resistor layer 3b can be alleviated; wherefore the resistor layer 3b is less prone to a micro crack. This helps reduce a resistance drift that occurs under the influence of the micro crack.
Note that, although trimming can be achieved in a sufficiently wide adjustment range with use of a single trimmable chip resistor 3, it is also possible to use a plurality of trimmable chip resistors 3 connected in series or in parallel with one another.
The trimmable chip resistors 3 is provided so as to be exposed outside when the mixer is attached to the high-frequency transmitting/receiving apparatus. This makes it possible to vary the resistance of the trimmable chip resistors 3 in a state where the mixer is attached to the high-frequency transmitting/receiving apparatus.
According to the embodiments of the mixer 6, 16 of the invention, by virtue of the trimmable chip resistor 3 provided as a pre-set variable resistor, in accordance with the Schottky-barrier diode (2, 45) acting as a high-frequency detection element such as the property of noise generated by the resistance component of the high-frequency detection element and the manner of mounting the Schottky-barrier diode (2, 45), a bias current is set at an appropriate value at the time of adjusting characteristics such as the mixing characteristics and the transmission characteristics of the mixer, and, at all other times such as an occasion where the mixer has been incorporated into a product, the bias current is maintained at the preset value. In this construction, in contrast to the case of controlling the electrical length of the adjustment mechanism formed so as to extend from the high-frequency detection element arranged in the high-frequency transmission line, not only is it possible to reduce a mechanical play present in the structure, but it is also possible to stabilize the working condition after the setting. As a result, the characteristics including the mixing characteristics and the transmission characteristics of the mixer can be tuned with high accuracy and stability. Moreover, in the absence of a movable part, the trimmable chip resistor 3 is able to act to maintain a determined resistance with stability in spite of occurrence of an external force such as vibration after adjustment. Thus, the trimmable chip resistor 3 is suitable for use as a pre-set variable resistor from a stable tuning standpoint.
Note that, in the invention, instead of the trimmable chip resistor 3 such as shown herein, it is also possible to use another type of pre-set variable resistor as described previously, so long as it demonstrates the following properties: its resistance can be adjusted to vary arbitrarily; a preset value is prevented from varying inadvertently; and the resistance is adjustable at least dozens of times. As the pre-set variable resistor, it is preferable to use an irreversible resistor such as the trimmable chip resistor 3.
In the mixer 6, 16 embodying the invention, the high-frequency transmission line is not limited to a coplanar line or a nonradiative dielectric line, but may be of another configuration such as a strip line, a micro-strip line, a coplanar line having a ground, a slot line, a waveguide, or a dielectric waveguide.
Next, the high-frequency transmitting/receiving apparatus 110 according to the first embodiment of the invention will be described. As shown in the block circuit diagram depicted in
In other words, the branching device 12 has two output portions 112b, 112c. An input portion 112a of the branching device 12 is connected to the high-frequency oscillator 11. The branching device 12 branches the high-frequency signal given by the high-frequency oscillator 11 so that the branched high-frequency signal components may be outputted from one output portion 112b and the other output portion 112c thereof, respectively. The modulator 13 is connected to the one output portion 112c and modulates the branched high-frequency signal component so as to output a high-frequency signal intended for transmission to the one output portion. When the high-frequency signal intended for transmission is given from the modulator 13 to the first terminal 14a, the circulator 14 acting as a signal separating device outputs the high-frequency signal intended for transmission which is inputted from the first terminal 14a, from the second terminal 14b and outputs a high-frequency signal which is inputted from the second terminal 14b, from the third terminal. In the mixer 16, one input end 16a is connected to the other output portion 112c of the branching device 12, and the other input end 12b is connected to the third terminal 14c. The mixer 16 mixes the branched high-frequency signal component outputted from the other output portion 112c and the high-frequency signal received by the transmitting/receiving antenna 15 so as to generate an intermediate frequency signal.
In the high-frequency transmitting/receiving apparatus, it is preferable that a transmission coefficient between the two input ends 16a and 16b of the mixer 16 is determined in such a way that the following expression holds: Pa2=Pb2. Specifically, a high-frequency signal passing through the modulator 13 placed in an OFF state is defined as Wa2, and a high-frequency signal that has been transmitted from the other output portion 112c of the branching device 12 to the output end 13b of the output portion of the modulator 13 by way of the mixer 16 and the circulator 14 and then reflected from the output end 13b of the modulator 13 is defined as Wb2. The intensity of the high-frequency signal Wa2 is represented by Pa2, whereas the intensity of the high-frequency signal Wb2 is represented by Pb2. Under these conditions, the transmission coefficient is adjusted so as for the expression Pa2=Pb2 to hold.
In the high-frequency transmitting/receiving apparatus, it is also preferable to determine the distance (line length) between one output end 12b of the branching device 12 and the modulator 13, or the distance (line length) between the output end 12c of the other output portion 112c of the branching device 12 and the output end 13b of the modulator 13, with the mixer 16 and the circulator 14 lying therebetween, in such a way that the following expression holds: δ=(2N+1)·π (N represents an integer), where δ represents the difference in phase between the high-frequency signals Wa2 and Wb2 at a center frequency. In order for the phase difference δ to be given by the expression δ=(2N+1)·π, the line length of the first dielectric strip line 22 which connects the high-frequency oscillator 11 and the modulator 13 and constitutes a part of the branching device 12 as shown in
Moreover, the high-frequency transmitting/receiving apparatus 110 of the invention shown in
More specifically, as shown in the plan view depicted in
In this construction, it is preferable that a transmission coefficient between the two input ends 16a and 16b of the mixer 16 is determined in such a way that the following expression holds: Pa2=Pb2. Specifically, a high-frequency signal that has been inputted to the second dielectric strip line 23 after passing through the modulator 13 placed in an OFF state, that is the modulator 13 in a state where a bias voltage is not applied, is defined as Wa2, and a high-frequency signal that has been transmitted from the mutually adjacent or coupled portions of the first dielectric strip line 22 and the fifth dielectric strip line 27 as well as the mutually adjacent or coupled portions of the fifth dielectric strip line 27 and the fourth dielectric strip line 26 to the output end 13b of the modulator 13 through the circulator 14, then reflected from the output end 13b of the modulator 13, and eventually inputted to the second dielectric strip line 23 is defined as Wb2. The intensity of the high-frequency signal Wa2 is represented by Pa2, whereas the intensity of the high-frequency signal Wb2 is represented by Pb2. Under these conditions, the transmission coefficient is adjusted so as for the expression Pa2=Pb2 to hold. The transmission coefficient between the two input ends 16a and 16b of the mixer 16 can be adjusted to a desired value by utilizing the tuning function of the mixer of the invention.
In this construction, it is also preferable that the distance (line length) between the mutually adjacent or coupled portions of the first dielectric strip line 22 and the fifth dielectric strip line 27 (the section for constituting the branching device 12) and the other end of the first dielectric strip line 22 (corresponding to the distance (line length) between the branching device 12 and the modulator 13) or the sum of the distance (line length) between the mutually adjacent or coupled portions of the first dielectric strip line 22 and the fifth dielectric strip line 27 and the other end of the fifth dielectric strip line 27; the line length of the fourth dielectric strip line 26; and the line length of the second dielectric strip line 23 (corresponding to the distance (line length) between the mixer 16-side portion of the branching device 12 and the modulator 13) is determined in such a way that the following expression holds: δ=(2N+1)·π. Specifically, a high-frequency signal passing through the modulator 13 placed in an OFF state is defined as Wa2, and a high-frequency signal that has been transmitted from the mutually adjacent or coupled portions of the first dielectric strip line 22 and the fifth dielectric strip line 27 to the output end 13b of the modulator 13 through the mixer 16, the fourth dielectric strip line 26, and the circulator 14, and then reflected from the output end 13b of the modulator 13 is defined as Wb2. δ represents the difference in phase between the high-frequency signals Wa2 and Wb2 at a center frequency. Under these conditions, the line length is adjusted so as for the expression δ=(2N+1)·π to hold. Note that, as described above, the first and fifth dielectric strip lines 22 and 27 constitute the branching device 12 at their mutually adjacent or coupled portions.
In
In this construction, the modulator 13 is designed as follows. As shown in the perspective view depicted in
In the invention, such a transmissive modulator as described just above is suitable for use as the modulator 13 of the high-frequency transmitting/receiving apparatus. Instead of the transmissive modulator, it is also possible to use a switching device that allows transmission and reflection of high-frequency signals, such as a semiconductor switch or a MEMS (Micro Electro Mechanical System) switch.
The high-frequency transmitting/receiving apparatus 110 of the invention shown in
As another advantage, the transmission coefficient between the two input ends 16a and 16b of the mixer 16 is determined in such a way that the expression Pa2=Pb2 holds. Specifically, a high-frequency signal passing through the modulator 13 placed in an OFF state is defined as Wa2, and a high-frequency signal that has been transmitted from the other output end 12c of the branching device 12 to the output end 13b of the modulator 13 by way of the mixer 16 and the circulator 14 and then reflected from the output end 13b of the modulator 13 is defined as Wb2. The intensity of the high-frequency signal Wa2 is represented by Pa2, whereas the intensity of the high-frequency signal Wb2 is represented by Pb2. Under these conditions, the transmission coefficient is adjusted so as for the expression Pa2=Pb2 to hold. In this case, the high-frequency signals Wa2 and Wb2 interfere with each other thereby to cause attenuation. This makes it possible to realize a high-frequency transmitting/receiving apparatus that is remarkable for constructional simplicity yet offers excellent transmission and reception performance, with high transmission power ON/OFF ratio, by preventing part of a high-frequency signal intended for transmission from being transmitted as an unwanted signal when the modulator 13 is kept in an OFF state.
By substantially equating the intensity Pa2 of the high-frequency signal Wa2 (unit: watt) with the intensity Pb2 of the high-frequency signal Wb2 (unit: watt), it is possible to cause the high-frequency signals Wa2 and Wb2 to interfere and weaken with each other effectively. That is, when the high-frequency signals Wa2 and Wb2 are synthesized, the resultant signal intensity is far smaller than the actual sum of the intensity Pa2 and Pb2: Pa2+Pb2. For this reason, it is desirable to satisfy the expression Pa2=Pb2. Theoretically, such a phenomenon takes place when two high-frequency signals interfere with each other. On the other hand, if the relationship between Pa2 and Pb2 is given by: Pa2≠Pb2, the high-frequency signals Wa2 and Wb2 interfere with each other insufficiently, with the result that there is not much difference between the signal intensity as observed when the high-frequency signals Wa2 and Wb2 are synthesized and the actual sum of the intensity Pa2 and Pb2: Pa2+Pb2. This makes it impossible to suppress production of an unwanted high-frequency signal when the modulator 13 is kept in an OFF state, leading to failure of attaining high ON/OFF ratio.
As still another advantage, the distance (line length) between one output end 12b of the branching device 12 and the modulator 13, or the distance (line length) between the other output end 12c of the branching device 12 and the output end 13b of the modulator 13, with the mixer 16 and the circulator 14 lying therebetween, is determined in such a way that the following expression holds: δ=(2N+1)·π (N represents an integer): where δ represents the difference in phase between the high-frequency signals Wa2 and Wb2 at a center frequency. In this case, in the region between the output end 13b of the modulator 13 and the circulator 14, the high-frequency signals Wa2 and Wb2 are synthesized in phase opposition and cancel out each other thereby to cause attenuation most effectively. This makes it possible to realize a high-frequency transmitting/receiving apparatus that offers excellent transmission and reception performance, with high transmission power ON/OFF ratio, by effectively preventing part of a high-frequency signal intended for transmission from being transmitted as an unwanted signal when the modulator 13 is kept in an OFF state.
Further, in the above constitution, it is preferable that an output end of the mixer 16 is provided with a switch 17 which performs opening/closing (switching) in accordance with an open/close controlling signal from the outside. When the switch 17 for performing opening/closing (switching) in accordance with the open/close controlling signal from the outside is provided on the output end of the mixer 16, that is the output portion 16c for outputting the generated intermediate frequency signal, even if, for example, an insufficient isolation between the first terminal 14a of the circulator 14 and the third terminal 14c causes a leakage of a part of the high-frequency signal intended for transmission into the third terminal 14c of the circulator 14, it is possible to operate the switch 17 so as to cut off such an intermediate frequency signal in order not to output the intermediate frequency signal to the leaked high-frequency signal and therefore, the high-frequency signal to be received can be made to be easily identified.
Next, the high-frequency transmitting/receiving apparatus 120 according to the second embodiment of the invention will be described. As shown in the block circuit diagram depicted in
Moreover, the high-frequency transmitting/receiving apparatus 120 of the invention shown in
More specifically, as shown in the plan view depicted in
The high-frequency transmitting/receiving apparatus 120 of the invention thus constructed is similar to the conventional high-frequency transmitting/receiving apparatus in terms of operation. However, in the high-frequency transmitting/receiving apparatus, by virtue of the mixer 16 of the invention, the mixing characteristics and the transmission characteristics of the mixer can be tuned appropriately in accordance with the property of the Schottky-barrier diode 45 acting as a high-frequency detection element, such as characteristics of noise generated by a resistance component of the Schottky-barrier diode 45, and the manner of mounting the Schottky-barrier diode 45. This makes it possible to realize a high-performance high-frequency transmitting/receiving apparatus that offers excellent reception sensitivity with stability.
Further, in the above constitution, it is preferable that an output end of the mixer 16 is provided with a switch 17 which performs opening/closing (switching) in accordance with an open/close controlling signal from the outside. When the switch 17 for performing opening/closing (switching) in accordance with the open/close controlling signal from the outside is provided on the output end of the mixer 16, that is the output portion 16c for putting the generated intermediate frequency signal, even if, for example, an insufficient isolation between the transmitting antenna 19 and the receiving antenna 20 causes a leakage of a part of the high-frequency signal intended for transmission into the receiving antenna 20, it is possible to operate the switch 17 so as to cut off such an intermediate frequency signal in order not to output the intermediate frequency signal to the leaked high-frequency signal and therefore, the high-frequency signal to be received can be made to be easily identified.
Next, the high-frequency transmitting/receiving apparatus 130 according to the third embodiment of the invention will be described with reference to
In other words, the RF selector switch 71 has an input portion 171a and two output portions 171b, 171c, of which input portion 171a is connected to the high-frequency oscillator 11. The RF selector switch 71 selectively outputs the high-frequency signal given by the high-frequency oscillator 11 to one output portion 171b or the other output portion 171c. The second RF selector switch 72 provided as a signal separating device has the first terminal 72b, the second terminal 72a, and the third terminal 72c. By switching a connection mode among the first terminal 72b, the second terminal 72a, and the third terminal 72c, the high-frequency signal intended for transmission is given from the RF selector switch 71 to the first terminal 72b so that the high-frequency signal inputted from the first terminal 72b is outputted from the second terminal 72a, and the high-frequency signal inputted from the second terminal 72a is outputted from the third terminal 72c. The mixer 16 is connected to the other output portion 171c of the RF selector switch 71 and the third terminal 72c of the second RF selector switch 72.
Further, in the above constitution, it is preferable that an output end of the mixer 16 is provided with a switch 17 which performs opening/closing (switching) in accordance with an open/close controlling signal from the outside.
When the high-frequency signal intended for transmission is outputted from the transmitting/receiving antenna 15, a control signal is given from the outside to the selector switch 71 and the second selector switch 72 so that the high-frequency signal given to the input portion 171a is outputted from one output portion 171b in the selector switch 71, and the high-frequency signal given to the first terminal 72b is given to the second terminal 72a in the second selector switch 72. Moreover, when the high-frequency signal is received by the transmitting/receiving antenna 15, the control signal is given from the outside to the selector switch 71 and the second selector switch 72 so that the high-frequency signal given to the input portion 171a is outputted from the other output portion 171c in the selector switch 71, and the high-frequency signal given to the first terminal 72b is given to the third terminal 72c in the second selector switch.
Moreover, the high-frequency transmitting/receiving apparatus 140 according to the fourth embodiment of the invention will be described with reference to
Further, in the above constitution, it is preferable that an output end of the mixer 16 is provided with a switch 17 which performs opening/closing (switching) in accordance with an open/close controlling signal from the outside.
When the high-frequency signal intended for transmission is outputted from the transmitting/receiving antenna 15, a control signal is given from the outside to the selector switch 71 so that the high-frequency signal given to the input portion 171a is outputted from one output portion 171b in the selector switch 71. Moreover, when the high-frequency signal is received by the transmitting/receiving antenna 15, the control signal is given from the outside to the selector switch 71 so that the high-frequency signal given to the input portion 171a is outputted from the other output portion 171c in the selector switch 71
Next, the high-frequency transmitting/receiving apparatus 150 according to the fifth embodiment of the invention will be described. As shown in the block circuit diagram depicted in
Next, the high-frequency transmitting/receiving apparatus 160 according to the sixth embodiment of the invention will be described. As shown in the block circuit diagram depicted in
In each of the high-frequency transmitting/receiving apparatuses 130, 140, 150, 160 embodying the invention, the high-frequency transmission line for use should preferably be selected from among a nonradiative dielectric line, a dielectric waveguide line, a waveguide, a dielectric waveguide, a strip line, a micro-strip line, a coplanar line, and a slot line.
Moreover, both the RF selector switch 71 and the second RF selector switch 72 may be designed in analogy to the design of the modulator 13.
Preferably, the RF selector switch 71 is provided with a branching device for branching an inputted high-frequency signal so that the branched high-frequency signal components may be outputted to one output end and the other output end thereof, respectively, and first and second PIN diodes connected to one output end and the other output end of the branching device, respectively. At least one of the first and second PIN diodes is connected with a bias circuit for applying a bias voltage in a forward direction. In this case, at least one of the first and second PIN diodes exhibits a low impedance, and therefore, even if switching is made to the first and second PIN diodes, the impedance can constantly be kept low and stabilized, when viewed as from the high-frequency signal input side (the high-frequency oscillator 11 side). This makes it possible to suppress load variation in the high-frequency oscillator 11 without employing an isolator or the like device, and thereby stabilize the oscillation frequency of the high-frequency signal.
In any of the high-frequency transmitting/receiving apparatuses 110, 120, 130, 140 embodying the invention, by virtue of the mixer of the invention, the mixing characteristics and the transmission characteristics of the mixer can be tuned appropriately in accordance with the property of the high-frequency detection element and the manner of mounting the high-frequency detection element. This makes it possible to realize a high-performance high-frequency transmitting/receiving apparatus that offers excellent reception sensitivity with stability.
In the high-frequency transmitting/receiving apparatus embodying the invention, each of the first through sixth dielectric strip lines 22, 23, 25 to 27, 32, 33, 35 to 37, and 39 should preferably be made of a resin material such as tetrafluoroethylene or polystyrene, and a ceramic material such as cordierite (2MgO.2Al2O3.5SiO2) ceramics having a low permittivity, alumina (Al2O3) ceramics, and glass ceramics. These materials exhibit low loss to high-frequency signals in a millimeter-wave band.
Moreover, although the first through sixth dielectric strip lines 22, 23, 25 to 27, 32, 33, 35 to 37, and 39 are each given a substantial rectangular cross-sectional profile basically in one virtual plane perpendicular to an extending direction, they may have their corners rounded off. That is, the dielectric strip line may have a cross-sectional profile of various shapes so long as high-frequency signals are transmitted properly.
As a material used for the ferrite plate 24, 34, it is preferable to use a zinc-nickel-iron composite oxide (ZnaNibFecOx) that is particularly desirable to high-frequency signals.
Moreover, although the ferrite plate 24, 34 is disc-shaped as is normally the case, it may have the shape of a regular polygon, as viewed plane-wise, that is as viewed from one side of a thickness direction. In this case, given the number of dielectric strip lines connected thereto of n (n represents an integer of 3 or more), then the planar configuration of the ferrite plate should preferably be m-sided regular polygon (m represents an integer of 3 or more, wherein m>n).
As a material used for the parallel plate conductor 21, 31 and the non-illustrated pair fellow thereto, it is preferable to use a conductor plate made of Cu, Al, Fe, Ag, Au, Pt, SUS (stainless steel), brass (Cu—Zn alloy), or the like material, from the viewpoint of high electric conductivity and excellent processability. It is also possible to use an insulation plate made of ceramics or resin having layers of such conductor materials as mentioned above formed on the surface thereof.
The nonreflective terminator 28, 38a, and 38b are connected with the fifth dielectric strip line 27, the fourth dielectric strip line 36, and the fifth dielectric strip line 37, respectively. Such a nonreflective terminator is fabricated by attaching a film-like resistive element or wave absorber to the upper and lower ends of each side face (the face disposed in face-to-face relationship with neither the inner face of the parallel plate conductor 21, 31 nor the inner face of the non-illustrated pair fellow thereto) at the end of its corresponding dielectric strip line. At this time, a nickel-chromium alloy or carbon is suitable for use as the resistive element, while permalloy or sendust is suitable for use as the wave absorber. By using such a material, it is possible to attenuate millimeter-wave signals with high efficiency. Note that the resistive element or wave absorber may be formed of any other given material so long as it enables attenuation of millimeter-wave signals.
The substrate 40, 44 is fabricated by forming, on one main surface of a platy base substrate made of tetrafluoroethylene, polystyrene, glass ceramics, glass epoxy resin, epoxy resin, and thermoplastic resin such as so-called liquid crystal polymer, the choke-type bias supply line 41, 46 formed of a strip conductor or the like made of aluminum (Al), gold (Au), copper (Cu), and the like metal.
It should be noted that a distinctive feature of the high-frequency transmitting/receiving apparatus 110, 120, 130, 140 of the invention is to include the mixer of the invention. In this construction, the high-frequency transmission line for providing connection among the circuit elements is not limited to the nonradiative dielectric line, but may be of another configuration such as a waveguide, a dielectric waveguide, a strip line, a micro-strip line, a coplanar line, a slot line, a coaxial line, or a modified form of a high-frequency transmission line of such a kind. The form selection is made in consideration of the frequency band for use and purposes. Moreover, the usable frequency band corresponding to high-frequency signals is not limited to a millimeter-wave band, but may be of a micro-wave band, or even below.
Instead of the circulator 14, it is possible to use a duplexer, a switch, a hybrid circuit, or the like. Moreover, for constituting the high-frequency oscillator, the modulator, and the mixer, it is possible to use a bipolar transistor, a field-effect transistor (FET), or an integrated circuit using such elements (CMOS, MMIC, etc) instead of a diode.
Next, a description will be given below as to a radar apparatus embodying the invention, a vehicle equipped with the radar apparatus, and a small boat equipped with the radar apparatus.
The radar apparatus according to one embodiment of the invention includes one of the high-frequency transmitting/receiving apparatuses of the invention and a distance information detector for detecting data on a distance to an object to be detected by processing the intermediate-frequency signal outputted from the high-frequency transmitting/receiving apparatus.
According to the radar apparatus of the invention, the high-frequency transmitting/receiving apparatus of the invention included therein enjoys higher performance, that is, offers excellent reception sensitivity with stability and allows transmission of high-frequency signals with high transmission power ON/OFF ratio. Thus, not only it is possible to detect an object to be detected swiftly without fail, but it is also possible to detect both nearby and far-off target objects successfully without fail.
The radar-bearing vehicle of the invention is equipped with the radar apparatus of the invention described just above. The radar apparatus is used to detect an object to be detected.
By virtue of its structure, the radar-bearing vehicle of the invention is, like a conventional radar-bearing vehicle, capable of controlling its behavior on the basis of the distance information detected by the radar apparatus and warning a driver of, for example, presence of an obstruction on the road or approach of other vehicles by sound, light, or vibration. In addition to that, in the radar-bearing vehicle of the invention, the radar apparatus acts to detect swiftly an object to be detected, for instance, an obstruction on the road or other vehicles without fail. This makes it possible to exercise proper control of the vehicle and to give a driver a warning appropriately without causing abrupt actions in the vehicle.
Further, even if the vehicle vibrates, the above described resistance of the trimmable chip resistor 3 is not caused to vary, and moreover even if the radar apparatus is disposed outside the vehicle, the resistance is hard to vary against temperature and moisture variation and therefore, the predetermined mixing characteristics and transmission characteristics can be favorably maintained so that the stable radar apparatus can realize a stable operation for detection.
Specifically, the radar-bearing vehicle of the invention finds a wider range of applications including a bicycle, a motor-assisted bicycle, a ride designed for use in an amusement park, and a cart used in a golf course, let alone a steam train, an electric train, an automobile, and a truck for transportation.
The radar-bearing small boat of the invention is equipped with the radar apparatus of the invention described above. The radar apparatus is used to detect an object to be detected.
By virtue of its structure, the radar-bearing small boat of the invention is, like a conventional radar-bearing vehicle, capable of controlling its behavior on the basis of the distance information detected by the radar apparatus and warning an operator of, for example, presence of an obstruction such as a reef or approach of other vessels or crafts by sound, light, or vibration. In addition to that, in the radar-bearing small boat of the invention, the radar apparatus acts to detect swiftly an object to be detected, for instance, an obstruction such as a reef or other vessels or crafts without fail. This makes it possible to exercise proper control of the small boat and to give an operator a warning appropriately without causing abrupt actions in the small boat.
Further, even if the boat vibrates, the above described resistance of the trimmable chip resistor 3 is not caused to vary, and more over even if the radar apparatus is disposed outside the boat, the resistance is hard to vary against temperature and moisture variation and therefore, the predetermined mixing characteristics, transmission characteristics and the like can be favorably maintained so that the stable radar apparatus can realize a stable operation for detection.
The radar-bearing small boat of the invention may be applied to boats of various kinds that can be operated by both licensed and unlicensed operators, specifically, a foyboat whose total tonnage is less than 20 tons; a dinghy; a wet bike; an outboat motor-mounted small bass fishing boat; an outboat motor-mounted inflatable boat (rubber boat); a fishing vessel; a leisure fishing boat; a working boat; an old-fashioned houseboat; a towing boat; a sport boat; a fishing boat; a yacht; an oceangoing yacht; a cruiser; and a pleasure boat whose total tonnage is 20 tons or above.
As described heretofore, according to the invention, there are provided: a mixer in which a bias supply circuit of a high-frequency detection element for constituting the mixer is provided with a pre-set variable resistor thereby to keep mixing characteristics and transmission characteristics of the mixer tuned satisfactorily; a high-frequency transmitting/receiving apparatus having the mixer that is remarkable for constructional simplicity and performance, and is capable of offering excellent reception performance, with high transmission power ON/OFF ratio, by preventing part of a high-frequency signal intended for transmission from being transmitted as an unwanted signal when a modulator is kept in an OFF state; a radar apparatus having the high-frequency transmitting/receiving apparatus of outstanding performance; a vehicle equipped with the radar apparatus; and a small boat equipped with the radar apparatus.
As an actual implementation example, the high-frequency transmitting/receiving apparatus 110 of the invention as shown in
Lastly, as the mixer 16, a balance-type mixer was formed as follows. As shown in
In the high-frequency transmitting/receiving apparatus thus constructed, at the outset, the resistance of the trimmable chip resistor 3 was adjusted properly. Then, a bias current passing through the Schottky-barrier diode 45 (2) of the mixer 16 was caused to vary within a range from 0 to 5 mA. In this state, the intensity Pa2 and Pb2 of the high-frequency signals Wa2 and Wb2 were measured in the following manner with use of a vector network analyzer designed for use in a millimeter-wave band. Firstly, the VCO was detached from the end of the waveguide so that a first test terminal (test port 1) of the vector network analyzer can be connected to the end. Subsequently, the transmitting/receiving antenna 19 was detached from the end of the third dielectric strip line 25 so that a second test terminal (test port 2) can be connected to the end. Then, the transmission characteristics S21 between the first and second test terminals was measured. At this time, in the case of conducting measurement on the high-frequency signal Wa2 transmitted through the modulator 13 placed in an OFF state, an electromagnetic wave-blocking metal plate is inserted between the first dielectric strip line 22 and the fifth dielectric strip line 27 to cut off the high-frequency signal Wb2. On the other hand, in the case of conducting measurement on the high-frequency signal Wb2 reflected from the output end 13b of the modulator 13, instead of the high-frequency modulation switch, an electromagnetic wave-blocking metal plate is inserted between the first dielectric strip line 22 and the second dielectric strip line 23 to cut off the high-frequency signal Wa2. That is, measurement of the transmission characteristics S21 was conducted for each of the high-frequency signals Wa2 and Wb2 on an individual basis. Here, under the condition that the intensity of a high-frequency signal outputted from the first test terminal is 0 dBm, the intensity Pa2 and Pb2 were derived on the basis of the measured values of the transmission characteristics S21.
As will be understood from
Next, the high-frequency transmitting/receiving apparatus 110 was operated under actual conditions to measure ON/OFF ratio characteristics at a bias current of 0 to 2.5 mA in the mixer. At the outset, the VCO was driven to oscillate stably, with its oscillation power kept invariant. Subsequently, the transmitting/receiving antenna 15 was detached from the end of the third dielectric strip line 25 so that a test terminal of a spectrum analyzer designed for use in a millimeter-wave band can be connected to the end. In this state, for each of the case where the modulator 13 is placed in an ON state and the case where it is placed in an OFF state, the intensity of a high-frequency signal outputted from the end was measured while performing frequency scanning step by step. Thereby, the ratio between two measurement values, namely, ON/OFF ratio, was obtained. The measurement results are shown in a chart depicted in
As will be understood from the measurement results shown in
When adjusting the mixing characteristics and transmission characteristics of the mixer, the resistance of the trimmable chip resistor 3 is made to be step-by-step larger from the lowest resistance of the trimmable chip resistor 3. By increasing the resistance of the trimmable chip resistor 3, it is possible to decrease the bias current passing through the Schottky-barrier diode 2. The resistance of the trimmable chip resistor 3 is increased until the current passing through the Schottky-barrier diode 2 reaches around 2.0 mA, thereby the transmission power ON/OFF ratio can be higher. Since the trimmable chip resistor 3 is an irreversible resistor, the adjustment of the mixing characteristics and transmission characteristics of the mixer is thus conducted by varying the bias current passing through the Schottky-barrier diode 2 in one direction, here by decreasing it.
Through an evaluation test similar to that conducted on the high-frequency transmitting/receiving apparatus of the invention thus far described, it has been confirmed that the high-frequency transmitting/receiving apparatus 120 of the invention also succeeds in providing high transmission power ON/OFF ratio.
Lastly, a radar apparatus equipped with the high-frequency transmitting/receiving apparatus of the invention was constructed. The radar apparatus was subjected to a radar detection test to evaluate its capability of detecting an approaching target object. It has been confirmed from the test result that the radar apparatus, in which tuning was made in the above-stated manner so as for the mixer to act properly, is capable of producing distance information swiftly without fail.
As described heretofore, according to the invention, there are provided: a mixer in which a bias supply circuit of a high-frequency detection element for constituting the mixer is provided with a pre-set variable resistor thereby to keep characteristics such as mixing characteristics and transmission characteristics of the mixer tuned satisfactorily; a high-frequency transmitting/receiving apparatus having the mixer that is remarkable for constructional simplicity and performance, and is capable of offering excellent reception performance, with high transmission power ON/OFF ratio, by preventing part of a high-frequency signal intended for transmission from being transmitted as an unwanted signal when a modulator is kept in an OFF state; and a radar apparatus capable of performing radar detection swiftly without fail.
It is to be understood that the application of the invention is not limited to the specific embodiments and examples described heretofore, and that many modifications and variations of the invention are possible within the spirit and scope of the invention. For example, the pre-set variable resistor may be constituted by a fixed resistor network formed by connecting together a plurality of fixed resistors, the contacts of which are relay switchable. In this case, the resistance of the fixed resistor network can be determined dynamically. For example, in response to changes in environmental conditions, a bias current present in the mixer 16 can be changed dynamically so as for the mixer 16 to act appropriately, or the bias current present in the mixer 16 can be changed in synchronization with the operation of the modulator 13.
The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and the range of equivalency of the claims are therefore intended to be embraced therein.
| Number | Date | Country | Kind |
|---|---|---|---|
| P2004-191733 | Jun 2004 | JP | national |
