Patent Grant
7277063
This invention relates to a variable directivity antenna and a variable directivity antenna system using such antennas.
A directional antenna may be used to receive a radio wave from a particular direction better than waves from other directions. A Yagi antenna is well-known as a directional antenna. A variable directivity antenna is used to selectively receive a desired one of radio waves from various directions. An example of variable directivity antenna is disclosed in Japanese Utility Model Publication No. SHO 63-38574 Y2 published on Oct. 12, 1988.
The variable directivity antenna disclosed in this Japanese UM publication includes first and second antennas which lie to orthogonally intersect with each other in the same horizontal plane. Dipole antennas or folded dipole antennas are used as the first and second antennas. A signal received by the first antenna is applied through a first variable attenuator to a combiner, and a signal received by the second antenna is applied through a second variable attenuator to the combiner. The directivity of the variable directivity antenna can be varied by adjusting the amounts of attenuation provided by the first and second variable attenuators.
A Yagi antenna can receive better a radio wave from a fixed, particular direction, but it cannot receive well radio waves from other directions. The above-described variable directivity antenna has directivity that can rotate, and, therefore, it can receive only a radio wave from a desired direction selected from radio waves from various directions. However, the variable directivity antenna of Japanese Utility Model Publication No. SHO 63-38574 Y2 has an “8”-shaped directivity pattern, and, therefore, the antenna receives also a radio wave from the direction opposite to the desired direction. In other words, the antenna of Japanese Utility Model Publication No. SHO 63-38574 Y2 has a low F/B ratio.
An object of the present invention is to provide a small-sized antenna that has an improved F/B ratio and can selectively receive well radio waves from different two directions. Another object of the present invention is to provide an antenna system that can selectively receive desired ones of radio waves from various directions satisfactorily, by the use of the variable directivity antennas.
A variable directivity antenna according to one embodiment of the present invention has a first antenna group. The first antenna group includes first and second antennas for receiving radio waves in a first frequency band, which exhibit an 8-shaped directivity along a line perpendicular to the length direction of the antennas and are disposed in parallel with each other, being spaced from each other by a distance shorter than a half (½) of the wavelength of the first frequency band. Phase shifting means adjusts the phase of signals received by the first and second antennas and combines them, in such a manner that a resulting combined signal can be in selected one of a first directivity state in which the resultant signal exhibits directivity in a first direction, which is from the first antenna toward the second antenna, and a second directivity state in which the resultant signal exhibits directivity in a second direction, which is from the second antenna toward the first antenna.
The phase shifting means may include combining means to which the received signals from the first and second antennas are coupled. A first fixed phase shifter is disposed between the combining means and the first antenna. Variable phase shifting means is disposed between the second antenna and the said combining means. In the first directivity state, the variable phase shifting means couples the received signal from the second antenna as it is to the combining means, and, in the second directivity state, a second fixed phase shifter is connected between the second antenna and the combining means. The amount of phase shift provided by the first fixed phase shifter is so determined that, in the first directivity state, the received signals coming along the second direction received by the first and second antennas can have substantially opposite phases. The amount of phase shift provided by the second fixed phase shifter is so determined that, in the second directivity state, the received signal from the second antenna can be in substantially opposite phase with the output signal of the first fixed phase shifter.
The received signals from the first and second antennas are amplified respectively in first and second amplifiers and, then, coupled to the phase shifting means.
The first and second antennas may be formed on a single printed circuit board.
The first and second antennas may be first and second dipole antennas having their length so selected as to be able to receive radio waves in the first frequency band. Outward of the opposite ends of each dipole antenna, extension elements are disposed in line with that dipole antenna. The total length of the first dipole antenna and its extension elements disposed outward of the opposite ends of the first dipole antenna is determined such as to be able to receive radio waves in a second frequency band, which is lower than the first frequency band. The total length of the second dipole antenna and its extension elements disposed outward of the opposite ends of the second dipole antenna is determined such as to be able to receive radio waves in the second frequency band. Switching means are disposed between the first dipole antenna and the extension elements disposed outward of the opposite ends of the first dipole antenna, and between the second dipole antenna and the extension elements disposed outward of the opposite ends of the second dipole antenna.
A variable directivity antenna according to another embodiment of the present invention has first and second antenna groups. The first antenna group includes first and second antennas for receiving radio waves in a first frequency band, which exhibit an 8-shaped directivity along a line perpendicular to the length direction of the antennas and are disposed in parallel with each other, being spaced from each other by a distance shorter than a half (½) of the wavelength of the first frequency band. The second antenna group includes third and fourth antennas for receiving a radio wave in the first frequency band, which exhibit an 8-shaped directivity along a line perpendicular to the length direction of the third and fourth antennas and are disposed in parallel with each other, being spaced from each other by the said distance. The third and fourth antennas are disposed perpendicular to the first and second antennas. First phase shifting means adjusts the phase of received signals from the first and second antennas and combines them, in such a manner that a resulting combined signal can be in selected one of a first directivity state in which the resultant signal exhibits directivity in a first direction, which is from the first antenna toward the second antenna, and a second directivity state in which the resultant signal exhibits directivity in a second direction, which is from the second antenna toward the first antenna. Second phase shifting means adjusts the phase of received signals from the third and fourth antennas and combines them, in such a manner that a resulting combined signal can be in selected one of a third directivity state in which the resultant signal exhibits directivity in a third direction, which is from the third antenna toward the fourth antenna, and a fourth directivity state in which the resultant signal exhibits directivity in a fourth direction, which is from the fourth antenna toward the third antenna. Signal combining means adjusts the value of an output signal of the first phase shifting means in the first or second directivity state and the value of an output signal of the second phase shifting means in the third or fourth directivity state, combines the adjusted output signals, and develops an output signal exhibiting selective one of directivities in the first through fourth directions and directions between the respective ones of the first through fourth directions.
The signal combining means may include first level adjusting means, to which an output signal of the first phase shifting means is coupled. In this arrangement, an output signal of the second phase shifting means is coupled to second level adjusting means. Output signals of the first and second level adjusting means are combined in combining means. Each of the first and second level adjusting means is adapted to selectively assume a first factor state in which a signal inputted thereto is outputted with a level proportional to a first factor, a second factor state in which a signal inputted thereto is outputted with a level proportional to a second factor smaller than the first factor, and an intercepting state in which a signal inputted thereto is intercepted. Level control signal generating means provides first and second level control signals to first and second adjusting means. The first and second level control signals are switched successively to a first step in which the first level adjusting means assumes the first factor state and the second level adjusting means assumes the intercepting state, a second step in which the first level adjusting means assumes the first factor state and the second level adjusting means assumes the second factor state, a third step in which the first and second level adjusting means assume the first factor state, a fourth step in which the first level adjusting means assumes the second factor state and the second level adjusting means assumes the first factor state, a fifth step in which the first level adjusting means assumes the intercepting state and the second level adjusting means assumes the first factor state, a sixth step in which the first level adjusting means assumes the second factor state and the second level adjusting means assumes the first factor state, a seventh step in which the first and second level adjusting means assume the first factor state, and an eighth step in which the first level adjusting means assumes the first factor state and the second level adjusting means assumes the second factor state.
Directivity control signal generating means provides directivity control signals to the first and second antenna groups to change the directivities of the first and second antenna groups. In the first through fourth steps, the directivity control signals selectively place the directivities of the first and second antenna groups in a state in which the directivity of the first antenna group is in the first directivity state and the directivity of the second antenna group is in the third directivity state, and a state in which the directivity of the first antenna group is in the second directivity state and the directivity of the second antenna group is in the fourth directivity state. Further, in the fifth through eighth steps, the directivity control signals selectively place the directivities of the first and second antenna groups in a state in which the directivity of the first antenna group is in the second directivity state and the directivity of the second antenna group is in the third directivity state, and a state in which the directivity of the first antenna group is in the first directivity state and the directivity of the second antenna group is in the fourth directivity state.
The first through fourth antennas may be first through fourth dipole antennas having their length so selected as to be able to receive radio waves in the first frequency band. Outward of the opposite ends of each dipole antenna, extension elements are disposed in line with that dipole antenna. The total length of each of the first through fourth dipole antennas and the extension elements disposed outward of the opposite ends of that dipole antenna is determined such as to be able to receive radio waves in a second frequency band, which is lower than the first frequency band. Switching means are disposed between the first dipole antenna and the extension elements disposed outward of the opposite ends of the first dipole antenna, between the second dipole antenna and the extension elements disposed outward of the opposite ends of the second dipole antenna, between the third dipole antenna and the extension elements disposed outward of the opposite ends of the third dipole antenna, and between the fourth dipole antenna and the extension elements disposed outward of the opposite ends of the fourth dipole antenna, respectively. Switching control means opens the switching means when a radio wave in the first frequency band is to be received, and closes the switching means when a radio wave in the second frequency band is to be received.
Variable filter means may be used. The variable filter means includes a first variable filter which receives the received signals from the first antenna group and has its passband changed selectively to the first and second frequency bands in response to a first passband varying signal, and a second variable filter which receives the received signals from the second antenna group and has its passband changed in response to a second passband varying signal. Passband varying signal generating means provides the first and second passband varying signals to the first and second variable filters.
When the level control signal generating means and said directivity control signal generating means are generating the first and second level control signals and the directivity control signals to provide the antenna system with such a directivity as to receive a desired radio wave, the passband varying signal generating means provides the first and second variable filters with first and second passband varying signals to make the first and second variable filters pass therethrough the desired radio wave.
A receiving apparatus may be provided, to which the received signal is coupled from the antenna system through a transmission path. The receiving apparatus transmits, through the transmission path, antenna control data related to a channel of which the signal to be received is being transmitted through the transmission line.
The receiving apparatus may be provided with memory means for storing therein the antenna control data and data relating to the channels in correlation with each other. The first and second level control signals, the directivity control signals and the first and second passband varying signals for a desired channel are arranged to be generated in accordance with the antenna control data. When the receiving apparatus is receiving the desired channel, the antenna control data for the desired channel is read out of the memory means and transmitted through the transmission line to the level control signal generating means, the directivity control signal generating means and the passband varying signal generating means.
After the receiving apparatus is set to receive the desired channel, the first and second passband varying signals are applied to the first and second variable filters to make them pass the desired channel signal therethrough, and, while monitoring the receiving condition at the receiving apparatus, the first and second level control signals and the directivity control signals are changed to determine the first and second level control signals and the directivity control signals when an allowable receiving condition is attained. The data piece relating to the thus determined first and second level control signals and directivity control signals, and the data piece relating to the first and second passband varying signals applied by the passband varying signal generating means, are stored in the memory means as the antenna control data.
When the receiving condition for the desired channel signal at the receiving apparatus becomes intolerable, with the first and second passband varying signals being applied to the first and second variable filters to make them pass the desired channel signal therethrough, the first and second level control signals and the directivity control signals are successively changed, with the receiving condition at the receiving apparatus being monitored, and the first and second level control signals and the directivity control signals attained when the allowable receiving condition at the receiving apparatus is realized. The first and second level control signals and the directivity control signals attained in the allowable receiving condition are substituted for the previous data in the antenna control data relating to the first and second level control signals and the directivity control signals.
Received signals from the first through fourth antenna elements may be amplified in associated amplifying means.
The first and second antenna elements may be formed on a first printed circuit board, with the third and fourth antenna elements formed on a second printed circuit board.
A variable directivity antenna 1 according to a first embodiment of the present invention may be used to receive a radio wave in a first frequency band, e.g. in the UHF band (470-890 MHz) used for television broadcasting. As shown in
Feeding points 2a and 2b disposed in the center portion of the antenna element 2 are coupled to a matching device, for example, a balun 8. Similarly, feeding points 4a and 4b in the center portion of the antenna element 4 are coupled to a balun 10. The baluns 8 and 10 may be formed on the printed circuit board 6, too, together with the antenna elements 2 and 4. The outputs of the baluns 8 and 10 are amplified in amplifiers 11 and 13, respectively. The amplifiers 11 and 13 may be formed on the printed circuit board 6, too. The outputs of the amplifiers 11 and 13 are coupled through feeders 12 and 14 to inputs 16a and 16b, respectively, of combining means, e.g. a combiner 16. Combining the signals from the antenna elements 2 and 4 after they are amplified by the amplifiers 11 and 13, provides a better C/N ratio than amplifying the combiner output. The lengths of the feeders 12 and 14 are different from each other. For example, the feeder 12 may have a length of L+ΔL, whereas the feeder 14 may have a length of L. In other words, the feeder 12 has a length larger by ΔL than the feeder 14.
The value ΔL is determined in the following way. Let it be assumed that the side of the antenna 1 on which the antenna element 2 is disposed is the front side, and the side of the antenna 1 on which the antenna element 4 is disposed is the back side. A radio wave coming from a second direction, i.e. coming from the back, in parallel with the surface of the printed circuit board 6 and perpendicularly to the length direction of the antenna elements 2 and 4, is received by the antenna elements 2 and 4 and propagates through the feeders 12 and 14 to the inputs 16a and 16b of the combiner 16, respectively. The signal resulting from the radio wave from the second direction as received by the antenna element 2 has its phase delayed from the signal resulting from the same radio wave as received by the antenna element 4, by an amount corresponding to the distance d between the antenna elements 2 and 4, and reaches the input 16a of the combiner 16, being delayed by an amount corresponding to ΔL, the difference in length between the feeders 12 and 14. In other words, the signal based on the radio wave from the second direction received by the antenna element 2 has its phase delayed from the signal based on the same radio wave received by the antenna element 4, by an amount corresponding to ΔL+d, when they reach the inputs 16a and 16b of the combiner 16, respectively. The value ΔL is determined such that the two signals at the inputs of the combiner 16 are opposite in phase.
A radio wave coming from a first direction, i.e. coming from the front, in parallel with the surface of the printed circuit board 6 and perpendicularly to the length direction of the antenna elements 2 and 4, is received by the antenna elements 2 and 4 and propagates through the feeders 12 and 14 to the inputs 16a and 16b of the combiner 16, respectively. The signal resulting from the radio wave from the first direction as received by the antenna element 4 has its phase delayed from the signal resulting from the same radio wave from the first direction as received by the antenna element 2, by the amount corresponding to the distance d between the antenna elements 2 and 4. The delay is reduced by ΔL.
For example, ΔL is determined such as to provide a delay corresponding to about 0.37λ. Then, although the radio wave from the first direction or front received by the antenna element 4 has a phase difference of +λ/20 (=0.05λ) relative to the same radio wave from the front received by the antenna element 2, the signals from the antennas 2 and 4 resulting from that radio wave are combined with a phase difference equal to 0.32λ (=0.37λ−0.05λ) because they propagate through the feeders 12 and 14 before reaching the inputs 16a and 16b of the combiner 16. Also, the radio wave from the second direction or back received by the antenna element 4 has a phase difference of −0.05λ relative to the same radio wave from the back received by the antenna element 2. The signal from the antenna element 2 is provided with a delay of −0.37λ when it is transmitted through the feeder 12, and exhibits a phase difference of −0.42λ (=−0.05λ−0.37λ) relative to the signal from the antenna element 4 at the input 16a of the combiner 16. This phase difference is approximately Δ/2, and, therefore, the signal from the back of the antenna 1 is substantially cancelled.
Then, the signals resulting from the radio wave from the front of the antenna 1 received by the antenna elements 2 and 4 are combined with a reduced phase difference, whereas the signals resulting from the radio wave from the back received by the antenna elements 2 and 4 are combined, being substantially oppositely phased. As a result, the antenna 1 operates as a directional antenna with no backward main lobe. Generally, if the lengths of the feeders from the antenna elements 2 and 4 to the combiner 16 are equal, the distance d between the antenna elements 2 and 4 must be λ/4 in order to couple signals resulting from a radio wave from the front as received by the antenna elements 2 and 4, in phase with each other to the inputs 16a and 16b of the combiner 16, and to couple signals resulting from a radio wave from the back as received by the antenna elements 2 and 4, in opposite phase to the inputs 16a and 16b of the combiner 16. Such larger distance d of λ/4 makes the antenna larger. In contrast, according to the first embodiment of the present invention, the distance d between the antenna elements 2 and 4 can be smaller, e.g. λ/20, than λ/4 because the difference of ΔL is provided between the length of the feeder 12 and the length of the feeder 14, and, therefore, the size of the antenna 1 can be smaller.
The antenna 1 with the above-described arrangement is adapted to receive well only a radio wave coming from the front side of the antenna 1. However, it may become necessary for the antenna 1 to receive a radio wave coming thereto from the back. For that purpose, variable phase means, for example, a variable phase device 18 is connected to the input 16b of the combiner 16 as shown in
The variable phase device 18 has selecting means, for example, a selector switch 20 that has contacts 20a and 20b. The switch 20 also has a contact element 20c that is selectively brought into contact with the contacts 20a and 20b. The contact element 20c is connected to the feeder 14, and the contact 20a is connected to the input 16b of the combiner 16. Connected between the contacts 20a and 20b is a delay element, e.g. a delay line 22 having such a length as to provide a delay of 180° for the signal at the above-stated center frequency. With the contact 20a contacted by the contact element 20c, the signal transmitted through the feeder 14 is coupled to the input 16b of the combiner 16 without being delayed. With the contact 20b contacted by the contact element 20c, the signal transmitted through the feeder 14 has its phase inverted by the delay line 22 before being coupled to the input 16b of the combiner 16. The selector switch 20 may be an electronic selector switch, e.g. a semiconductor switching device. The semiconductor switching device may be, for example, a PIN diode. With an electronic selector switch, directivity switching can be remote controlled. The variable phase device 18 may be connected to the feeder 12 instead of the feeder 14. Further, the variable phase device 18 may be formed on the printed circuit board 6.
As described above, the antenna 1 exhibits directivity in selected one of the forward and backward directions, and can be small in size because it is formed on the printed circuit board 6.
The above-described antenna 1 is for receiving radio waves in the UHF band. An antenna 30 according to a second embodiment of the invention shown in
Outward of and close to the respective opposite outer ends of the antenna element 32, extension elements 36 and 38 are disposed in line with the antenna element 32. Similarly, extension elements 40 and 42 are disposed in line with the antenna element 34 outward of and close to the respective opposite outer ends of the antenna element 34. The extension elements 36, 38, 40 and 42 are also formed on the printed circuit board by etching metal layers on the board. The length of each of the extension elements 36, 38, 40 and 42 is about 100 mm. Accordingly, the sum in length of the antenna element 32 and its extension elements 36 and 38 is about 450 mm, and the sum in length of the antenna element 34 and its extension elements 40 and 42 is also about 450 mm.
Switching means, which may be semiconductor switching devices, e.g. PIN diodes 44 and 46, are connected between the outer ends of the antenna element 32 and the extension elements 36 and 38, respectively. The PIN diodes 44 and 46 have their anodes connected to the antenna element 32 and have their cathodes connected respectively to the extension elements 36 and 38. Similarly, PIN diodes 48 and 50 are connected between the outer ends of the antenna element 34 and the extension elements 40 and 42, respectively. The PIN diodes 44 and 46 have their anodes connected to the antenna element 34 and have their cathodes connected respectively to the extension elements 40 and 42. With the PIN diodes 44, 46, 48 and 50 being conductive, the antenna element 32 is connected to the extension elements 36 and 38, and the antenna element 34 is connected to the extension elements 40 and 42, so that the antenna elements 32 and 34 with their extension elements can operate as VHF antennas. With the PIN diodes 44, 46, 48 and 50 rendered nonconductive, only the antenna elements 32 and 34 operate and act as UHF antennas.
In order to render the PIN diodes 44, 46, 48 and 50 conductive and nonconductive, the extension elements 36, 38, 40 and 42 are connected to a point of reference potential, e.g. a point of ground potential, via respective current supply paths, e.g. high-frequency blocking coils 52, 54, 56 and 58. In order to cause DC current to flow from the antenna element 32 through the PIN diodes 44 and 46 and the high-frequency blocking coils 52 and 54, a switch 64 and a DC supply 68 are connected to a balun 60 to which central feed points of the antenna element 32 are connected. Similarly, in order to cause DC current to flow from the antenna element 34 through the PIN diodes 48 and 50 and the high-frequency blocking coils 56 and 58, a switch 66 and a DC supply 70 are connected to a balun 62 to which central feed points of the antenna element 34 are connected. Instead of using the DC supplies 68 and 70 in association with the switches 64 and 66, respectively, a single DC supply may be connected to the switches 64 and 66.
The baluns 60 and 62 have the same configuration, and, therefore, only the balun 62 is described in detail. Respective one ends of inductors 72 and 74 are connected to the two feeding points of the antenna element 34. The other end of the inductor 72 is grounded via a capacitor 76, and the other end of the inductor 74 is connected to an output terminal 78 of the balun 62. An inductor 80 is disposed with respect to the inductor 72 in such a way that they are inductively coupled with each other, and an inductor 82 is disposed with respect to the inductor 74 in such a way that they are inductively coupled with each other. The inductors 80 and 82 have their one ends interconnected, with the other end of the inductor 80 connected to the other end of the inductor 74, and with the other end of the inductor 82 connected to the other end of the inductor 72. A series combination of the switch 66 and the DC supply 70 is connected via a low-pass filter 84 to the junction of the inductors 74 and 80. The low-pass filter 84 includes a high-frequency blocking coil 84a and a capacitor 84b.
With the switch 66 closed, current from the DC supply 70 flows through the inductor 74, the antenna element 34 and the PIN diode 50 to the high-frequency blocking coil 58, and also flows through the inductors 80, 82 and 72, the antenna element 34, and the PIN diode 48 to the high-frequency blocking diode 56. This renders the PIN diodes 48 and 50 conductive for receiving the UHF band. If the switch 66 is opened, no DC current flows from the DC supply 70, rendering the PIN diodes 48 and 50 nonconductive, for receiving the UHF band.
Similarly, by opening or closing the switch 64 associated with the balun 60, the UHF or VHF band reception mode can be selected. It is desirable to operate the switches 64 and 66 in synchronization with each other. By using semiconductor switching devices as the switches 64 and 66, and supplying external switching control signals to the switches 64 and 66, remote control is possible.
The remainder of the antenna 30 is similar to the antenna 1 of
The above-described arrangement makes it possible to selectively receive radio waves in the UHF and VHF bands coming to the antenna 30 from the front and back thereof.
A variable directivity antenna system 90 according to a third embodiment of the invention is shown in
The antenna system 90 receives, at its input terminal 90a, a satellite broadcast intermediate-frequency signal resulting from a satellite broadcast signal received by a satellite broadcast receiving antenna, e.g. a satellite broadcast receiving parabolic antenna 92, and frequency-converting in a converter 94 provided in association with the parabolic antenna 92. The satellite broadcast intermediate-frequency signal is mixed with a UHF or VHF band television broadcast signal received by the antenna system 90, and the mixture signal is outputted from an output terminal 90b of the antenna system 90. The mixture signal at the output terminal 90b is coupled through a transmission line 96 to a splitter 98 where the mixture signal is split into the satellite broadcast intermediate-frequency signal and the VHF or UHF band television broadcast signal. The satellite broadcast intermediate-frequency signal is coupled to a satellite broadcast intermediate-frequency signal input terminal 100a of a receiving apparatus 100, and the VHF or UHF band television broadcast signal is coupled to a VHF/UHF band television broadcast signal input terminal 100b.
The antennas 30a and 30b of the antenna system 90 are disposed to orthogonally intersect with each other as shown in
Signals from the antennas 30a and 30b are coupled to variable filter means, e.g. variable filters 102 and 104. The variable filters 102 and 104 are bandpass filters each having a passband variable to a desired one of the UHF band and the VHF band, for example, and the passband is varied in response to a passband varying signal supplied by passband varying control means, e.g. a control unit 106. The passbands are varied so that the frequencies of the radio waves to be received by the antenna system 90 can lie in the passbands. In place of the bandpass filters, variable cutoff frequency high-pass or low-pass filters may be used. The cutoff frequencies of such high-pass or low-pass filters are so varied that the frequencies of the waves to be received can be within the passbands of the filters.
Output signals of the variable filters 102 and 104 are amplified in amplifiers 108 and 110, respectively, and coupled to level adjusting means, e.g. variable attenuators 112 and 114, respectively. The variable attenuators 112 and 114 may include a semiconductor device, e.g. a PIN diode, having its conductivity varied in response to a respective level control signal supplied to it from level control signal generating means, which may be the control unit 106. Variable gain amplifiers may be used in place of the variable attenuators 112 and 114.
The output of the variable attenuator 112 is the output signal from the amplifier 108 multiplied by a factor K1, and the output of the variable attenuator 114 is the output signal from the amplifier 110 multiplied by a factor K2. The factor K1 is variable in response to the level control signal for the variable attenuator 112, and the factor K2 is variable in response to the level control signal for the variable attenuator 114. As shown in
The control unit 106 provides the antennas 30a and 30b with frequency-band switching signals for switching the antenna 30a and 30b between the UHF receiving mode and the VHF receiving mode, i.e. selectively opening and closing the switches 64 and 66 shown in
Output signals of the variable attenuators 112 and 114 are combined with each other in combining means, e.g. a combiner 116. Thus, the directivity of the combined signal of the antennas 30a and 30b as combined in the combiner 116 can be varied to any desired direction by changing the factors K1 and K2, as is well known. Let it be assumed that the phase shifters 18b and 18c are so adjusted to provide, for example, the antenna 30a with the upward directivity in the plane of the sheet of
As described above, since the directivity of the antenna system 90 can be changed to any direction over 360°, it can receive well any desired one of radio waves from various directions. The control unit 106 controls the passbands of the variable filters 102 and 104 to pass therethrough the desired radio wave when it is being received by the antenna system 90, whereby the antenna system 90 is prevented from receiving undesired radio waves, which can improve a D/U ratio.
An output signal from the combiner 116 is amplified by an amplifier 118 and, then, coupled through a DC blocking capacitor 120 to a mixer 122. The mixer 122 receives also the satellite broadcast intermediate-frequency signal from the input terminal 90a of the antenna system 90. The output signal of the combiner 116 and the satellite broadcast intermediate-frequency signal are mixed with each other in the mixer 122, and the mixture signal developed at the output terminal 90b of the antenna system 90 is coupled via the transmission line 96 to the splitter 98 where the output signal of the mixer 116 and the satellite broadcast intermediate-frequency signal are separated for application to the satellite broadcast intermediate-frequency signal input terminal 100a of the receiving apparatus 100, and to the television broadcast signal input terminal 100b, as described previously.
A television broadcast signal processing unit of the receiving apparatus 100 includes, as shown in
The receiving apparatus 100 includes also memory means, e.g. a memory 131. The memory 131 stores therein antenna control data necessary for the antenna system 90 to receive desired radio waves (e.g. a television broadcast channel desired to be received). Such control data is stored, being correlated with corresponding channel data indicative of respective desired television broadcast channels, and indicates the receiving band to be received, i.e. the UHF or VHF band, the desired direction of directivity, the passbands of the variable bandpass filters, and the phase conditions of the variable phase devices 18b and 18c. When the tuner 126 reads out channel data from the memory 131, the associated antenna control data is supplied to an antenna control commander 132. The antenna control commander 132 converts the antenna control data to an FSK signal or an ASK signal. The resulting FSK or ASK signal is applied to the control unit 106 through the input terminal 100b, the splitter 98, the transmission line 96, the output terminal 90b of the antenna system 90, and the mixer 122. When receiving the FSK or ASK signal, the control unit 106 demodulates the FSK or ASK signal to the antenna control data. In accordance with the demodulated antenna control data, the switches 66 and 68 of the antennas 30a and 30b are ON-OFF controlled, the passbands of the variable filters 102 and 104 are modified, and the factors K1 and K2 for the variable attenuators 112 and 114 are altered, and the variable phase devices 18b and 18c of the antennas 30a and 30b are set to provide in-phase or 180°-out-of-phase condition.
In order for such control to be provided, it is necessary to store the receiving channel data and the corresponding antenna control data in association with each other, in the memory 131. For that purpose, the processing as shown in
First, an automatic channel mode is selected (Step S2). This causes the channel designating value in a channel counter n to be set to an initial value. The channel counter n is for designating a channel to be received. Then, the value in the channel counter n is increased by one for designating a certain channel to be received (Step S4), whereby this channel is selected in the tuner 126, and, at the same time, data for making the variable filters 102 and 104 have passbands for receiving that channel is transmitted from the antenna control commander 132 to the control unit 106. Then, the tuner 126 makes a judgment as to whether the selected channel is an analog_television broadcast channel or not (Step S6).
If the selected channel is an analog television broadcast channel, a command is transmitted from the antenna control commander 132 to the control unit 106 to successively change K1 and K2 and also to adjust the variable phase devices 18b and 18c to provide the in-phase or 180°-out-of-phase condition, whereby the direction of directivity of the antenna is successively changed. The reception level for each direction is measured in the tuner 126 and stored (Step S8). In Step S10, whether the directivity of the antenna has been measured for all the predetermined directions in the angular range of 360° or not is judged. If it has not, the execution of Steps S8 and S10 is repeated in loop until the answer to the query in Step S10 becomes YES. When the answer to the query in Step S10 becomes YES, whether or not the largest one of the measured levels is at or above a predetermined reference level is examined (Step S12). In other words, whether or not there is directivity providing an acceptable receiving condition is judged. If the answer is YES, the direction of directivity providing the largest reception level is stored together with the largest reception level in the memory 131 (Step S14). At the same time, the data representing the passbands of the variable filters 102 and 104, and the data indicating which condition, in-phase or 180°-out-of-phase condition, the variable phase devices 18b and 18c provided, employed when the largest reception level has been attained, are stored in the memory 131 in association with the largest directivity providing direction and the largest reception level. After that, whether the value in the channel counter n is the value for the last one of the receiving channels is judged (Step S16). If the answer is NO, it means that there are channels left for which the direction of directivity has not yet been determined. Then, the processing is repeated from Step S4 until the answer to the query in Step S16 becomes YES.
The answer of NO to the query in Step S12 indicates that there is a possibility that no radio wave is broadcast in that channel. In this case, Step S4 is executed to designate the next receiving channel.
If the selected channel is judged to be a digital television broadcast channel in Step S6, the direction of directivity of the antenna system 90 is varied, and the bit error rate (BER) for each direction is measured and stored (Step S18), as shown in
The answer of NO to the query in Step S22 may mean that no wave is broadcast in that channel, and, therefore, the processing is repeated from Step S4.
In this way, the storing in the memory 131 of the antenna control data necessary for the antenna system 90 to receive desired radio waves is completed.
It may occur that, while a radio wave of a certain television channel is being received by the tuner 126, a broadcast signal condition worsens to an unacceptable condition. In such a case, processing as shown in
Referring to
If it is judged, in Step S36, that the received signal level is lower than the reference level, the direction of antenna directivity is successively altered, and the signal level at each of the altered directions is measured and stored (Step S38). Then, whether the signal levels for all the predetermined directions in the 360° angular range have been measured and stored is judged (Step S40), and, if not, Steps S38 and S40 are repeated in loop until the answer to Step S40 becomes YES. When it is judged, in Step S40, that the signal levels at all of the predetermined directions have been measured and stored, the highest one of the measured signal levels is examined as to if it is equal to or above the reference level (Step S42). If the answer is YES, the direction in which the highest level is obtained and the reception level are stored in the memory 131 (Step S44). Then, the antenna directivity is set for that direction (Step S46), and the processing resumes from Step S34.
The answer of NO to the query in Step S42 may mean that the signal in the channel cannot be received in an allowable condition with any directivities or the signal has disappeared. Accordingly, the reception of the signal in that channel is abandoned.
If the desired signal to be received is judged to be a digital television broadcast channel signal in Step S30, the processing shown in
The answer of NO to the query in Step S58 may mean that the signal in the channel cannot be received in an allowable condition with any directivities or the signal has disappeared. Accordingly, the reception of the signal in that channel is abandoned.
A variable directivity antenna according to a fourth embodiment differs from the variable directivity antenna according to the third embodiment in the arrangement of the level adjusting means as shown in
For that purpose, the variable attenuator 1136a has switching elements, e.g. PIN diodes 1140a and 1142a connected in series between the amplifier 108 and the combiner 116. The PIN diode 1140a has its cathode connected to the output of the amplifier 108, the anodes of the PIN diodes 1140a and 1142a are connected together, and the cathode of the PIN diode 1142a is connected to the input of the combiner 116. The anodes of the PIN diodes 1140a and 1142a are connected through a resistor 1144a to a voltage supply unit 1146a, and the cathodes of the PIN diodes 1140a and 1142a are connected through high frequency blocking coils 1148a and 1150a, respectively, to a point of reference potential. Accordingly, when a positive voltage is coupled to the voltage supply unit 1146a, the PIN diodes 1140a and 1142a are rendered conductive, so that the signal from the amplifier 108 is coupled to the combiner 116 without being attenuated.
The variable attenuator 1136a has a fixed attenuator, e.g. a T-type attenuator 1154a. The attenuator 1154a is comprised of three resistors 1152a and provides attenuation of 7 dB. A switching element is connected to the input of the attenuator 1154a. For example, a PIN diode 1156a has its anode connected to the input of the attenuator 1154a, and has its cathode connected to the cathode of the PIN diode 1140a. Similarly, a switching element, e.g. a PIN diode 1158a has its anode connected to the output of the attenuator 1154a, and has its cathode connected to the cathode of the PIN diode 1142a. The junction of the three resistors of the T-type attenuator 1154a is connected through a resistor 1160a to a voltage supply unit 1162a. Accordingly, when a positive voltage is coupled to the voltage supply unit 1162a, the PIN diodes 1156a and 1158a are rendered conductive, so that the T-type attenuator 1154a is coupled between the amplifier 108 and the combiner 116, and, therefore, the signal from the amplifier 108 is attenuated by 7 dB.
Further, the variable attenuator 1136a has a matching resistor 1164a having an impedance equal to the impedance of the antenna 30a. The matching resistor 1164a has its one end connected to a point of reference potential, and has the other end connected through a DC blocking capacitor 1170a to a switching element, e.g. a PIN diode 1166a at its anode. The PIN diode 1166a has its cathode connected to the cathode of the PIN diode 1140a, and has its anode connected through a resistor 1172a to a voltage supply unit 1174a. Accordingly, when a positive voltage is coupled to the voltage supply unit 1174a, the PIN diode 1166a is rendered conductive, so that the output of the amplifier 108 is connected through the matching resistor 1164a to a point of reference potential, which results in infinite attenuation.
Since the arrangement of the variable attenuator 1136b is similar to the variable attenuator 1136a, a suffix “b” is substituted for the suffix “a” attached to the reference numerals for the components equivalent to the ones of the attenuator 1136a, and no description is made.
To attain a variable directivity described above in the multiple frequency band antenna, for the azimuth of from 0 degrees to 67.5 degrees, the antenna 30a is made to exhibit the forward directivity, with the antenna 30b made to exhibit the rightward directivity. For the azimuth of from 90 degrees to 157.5 degrees, the antenna 30a is made to exhibit the backward directivity, while the antenna 30b is made to exhibit the rightward directivity. For the azimuth angle of from 180 degrees to 247.5 degrees, the antenna 30a is made to exhibit the backward directivity, while the antenna 30b is made to exhibits the leftward directivity. For the azimuth angle of from 270 degrees to 387.5 degrees, the antenna 30a is made to exhibit the forward directivity, while the antenna 30b is made to exhibit the leftward directivity.
For the azimuth of from 0 degrees to 45 degrees, the variable attenuator 1154a provides zero (0) attenuation, but its attenuation increases from 7 dB to infinity (∞) for the angle of from 67.5 degrees to 90 degrees. The amount of attenuation decreases from 7 dB to zero (0) for the angle of from 112.5 degrees to 135 degrees, and remains zero (0) for the angle of from 157.5 degrees to 225 degrees. For the angle of from 247.5 degrees to 270 degrees, the amount of attenuation increases from 7 dB to infinity (∞), decreases from 7 dB to zero (0) for the angle of from 292.5 degrees to 315 degrees, and is zero (0) for the angle of 337.5 degrees.
As for the variable attenuator 1154b, the amount of attenuation decreases from infinity (∞) to 7 dB and to zero (0) for the azimuth angle of from 0 degrees to 45 degrees, and remains zero (0) for the angle of 67.5 degrees to 135 degrees. For the azimuth angle of from 157.5 degrees to 180 degrees, the amount of attenuation increases from 7 dB to infinity (∞). The amount of attenuation given by the variable attenuator 1154b decreases from 7 dB to zero (0) for the angle of from 202.5 degrees to 225 degrees, remains zero (0) for the angle of from 247.5 degrees to 315 degrees, and is 7 dB for 337.5 degrees. Like this, when the amount of attenuation of one attenuator is zero (0), the amount of attenuation of the other increases or decreases.
The variable attenuators 1154a and 1154b of this embodiment employ 7 dB as one of the variable amounts of attenuation. The reason why the value of 7 dB is employed is that the half-width of the combined directivity of the antenna system 90 is from 75 degrees to 80 degrees. If the half-width of the combined directivity of the antenna system 90 is different from the value of from 75 degrees to 80 degrees, an amount of attenuation other than 7 dB is employed. For example, if the half-width of the combined directivity of the antenna system 90 is wider than the range of 75 degrees to 80 degrees, the amount of attenuation employed is larger than 7 dB. If the half-width of the combined directivity of the antenna system 90 is narrower than the range of 75 degrees to 80 degrees, the amount of attenuation employed is smaller than 7 dB.
The antenna 1 shown in
In the antenna 1 shown in
The antenna system according to the third embodiment uses two antennas 30a and 30b, but the number is not limited to two, and a larger number of antennas may be used. Furthermore, instead of using dipole antennas as the antennas 30a and 30b, folded dipole antennas as used in the antenna 1 shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-099639 | Apr 2003 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2004/004793 | 4/1/2004 | WO | 00 | 9/27/2005 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2004/091043 | 10/21/2004 | WO | A |
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| Number | Date | Country | |
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| 20060050005 A1 | Mar 2006 | US |
