Patent Application
20110059712
The present invention relates to a portable radio and, more particularly, to a portable radio that is equipped with a plurality of antennas and a receiver, which is connected to the antennas and which enables performance of diversity operation, and that can assure high receiving performance by improving deterioration of an antenna gain resulting from electromagnetic field coupling of the plurality of antennas.
a) shows an example general configuration of a related art portable radio. The portable radio has a first antenna 11; a first amplifier 12 that amplifies a signal received by the first antenna 11; a second antenna 13 for performing diversity combination receiving; a second amplifier 14 for amplifying a signal received by the second antenna 13; and a DTV (Digital Television) tuner module 15 capable of performing diversity combination by means of an output from the first amplifier 12 and an output from the second amplifier 14.
The first amplifier 12 and the second amplifier 14 are set such that input impedance characteristics of operating bands of the amplifiers become equal to each other.
Specifically, the second 50-ohm impedance matching section 22 is connected to an input stage of the first amplifier 12, and the first amplifier is then packaged. A fifth 50-ohm impedance matching section 25 is connected to an input stage of the second amplifier 14, and the second amplifier is then packaged. In this case, the packaged first amplifier 12 and the packaged second amplifier 14 are set such that their input impedance characteristics acquired at operating bands become equal to each other.
When the first antenna 11 and the second antenna 13 are pullout whip antennas, or the like, and when the antennas are applied to a foldable portable radio, a first 50-ohm impedance matching section 21 and a fourth 50-ohm impedance matching section 24 are provided in order to compensate for an impedance change incidental to opening and closing actions of enclosures. A third 50-ohm impedance matching section 23 and a sixth 50-ohm impedance matching section 26 are further interposed between the first amplifier 12, the second amplifier 14 and the DTV tuner module 15.
Meanwhile, attention has been paid to an Orthogonal Frequency Division Multiplexing (OFDM) scheme characterized by multipath fading and high ghost resistance, as a modulation scheme appropriate for an application to mobile digital transmission, a terrestrial digital television broadcast, or a wireless LAN. A proposed OFDM modulated signal receiver includes amplifiers connected to respective antennas; detects a carrier-to-noise ratio; calculates a weighting coefficient commensurate with the detected carrier-to-noise ratio; and can perform diversity combination (see; for instance, Patent Document 1).
Patent Document 1: JP-A-2005-175878
However, the related art receiver has a potential fear of encountering deterioration of antenna performance, which would be caused by electromagnetic field coupling between the diversity combination antennas. In particular, applications operating at a frequency band that is lower than operating bands of a portable phone and a PHS; for instance, a digital television broadcast, undergo great influence.
The present invention has been conceived in light of the foregoing circumstance and aims at providing a portable radio that enables viewing of a highly sensitive application; for instance, a digital television broadcast, or the like, by improving deterioration of an antenna gain attributable to electromagnetic field coupling between the plurality of antennas.
A portable radio of the present invention includes: a first antenna; a second antenna; a first low noise amplifier electrically whose one end is electrically connected to the first antenna; a second low noise amplifier whose one end is electrically connected to the second antenna; and a receiving circuit electrically connected to a remaining end of the first low noise amplifier and a remaining end of the second low noise amplifier, wherein an input impedance of the first low noise amplifier and an input impedance of the second low noise amplifier entirely differ from each other in a predetermined operating frequency band of the receiving circuit.
In the above configuration, an input impedance of the first low noise amplifier and an input impedance of the second low noise amplifier entirely differ from each other in a predetermined operating frequency band of the receiving circuit, and no overlapping domain exists in a Smith chart. Therefore, an impedance of the first antenna in an input stage of the first low noise amplifier and an impedance of the second antenna in an input stage of the second low noise amplifier differ from each other; hence, electromagnetic field coupling between the first antenna and the second antenna is diminished, so that gain deterioration attributable to electromagnetic field coupling is improved. It is also possible to view a highly sensitive digital television broadcast by improving gain deterioration of the first antenna and gain deterioration of the second antenna.
A portable radio of the present invention includes: a first antenna; a first impedance matching section whose one end is electrically connected to the first antenna; a first low noise amplifier whose one end is electrically connected to a remaining end of the first impedance matching section; a second antenna; a complex conjugate matching section whose one end is electrically connected to the second antenna; a second low noise amplifier whose one end is electrically connected to a remaining end of the complex conjugate matching section; a second impedance matching section whose one end is electrically connected to a remaining end of the second low noise amplifier; and a receiving circuit electrically connected to a remaining end of the first low noise amplifier and a remaining end of the second impedance matching section, wherein the first impedance matching section matches the input impedance of the first low noise amplifier to a predetermined input impedance of the receiving circuit, and wherein the complex conjugate matching section matches an impedance of the second antenna and an impedance of an input stage of the second low noise amplifier to a complex conjugate impedance; and the second impedance matching section matches an output impedance of the second low noise amplifier to a predetermined input impedance of the receiving circuit.
In the configuration, the complex conjugate matching section matches an impedance of the second antenna and an impedance of an input stage of the second low noise amplifier to a complex conjugate impedance. Therefore, even when the impedance of the second antenna has greatly differed from the input impedance of the second low noise amplifier, it becomes possible for a matching circuit entailing a little loss to perform matching. Moreover, the impedance of the first antenna is acquired by matching the input impedance of the first low noise amplifier to the predetermined input impedance of the receiving circuit. On the contrary, the impedance of the second antenna and the impedance of the input stage of the second low noise amplifier are matched to the complex conjugate impedance. Therefore, the impedance of the first antenna of the input stage of the first low noise amplifier and the impedance acquired as a result of the second antenna of an input stage of the second low noise amplifier being connected to the complex conjugate matching section can be made differ from each other, so electromagnetic field coupling between the first antenna and the second antenna can be diminished. Therefore, it is possible to view a highly sensitive digital television broadcast.
The portable radio of the present invention further includes: a third impedance matching section whose one end is electrically connected to the first antenna and whose remaining end is electrically connected to one end of the first impedance matching section, wherein the third impedance matching section matches an output impedance of the first antenna to a predetermined input impedance of the receiving circuit.
In the configuration, the third impedance matching section matches the impedance of the first antenna to a predetermined input impedance of the receiving circuit. Accordingly, a received signal loss can further be reduced and supplied to the receiving circuit more effectively.
The portable radio of the present invention further includes a fourth impedance matching section whose one end is electrically connected to a remaining end of the first low noise amplifier and whose remaining end is electrically connected to the receiving circuit, wherein the fourth impedance matching section matches an output impedance of the first low noise amplifier to a predetermined input impedance of the receiving circuit.
In the configuration, the fourth impedance matching section matches an output impedance of the first low noise amplifier to a predetermined input impedance of the receiving circuit. Hence, it becomes possible to reduce an output loss of the first low noise amplifier, thereby more effectively supply the output to the receiving circuit.
The portable radio of the present invention further comprises a diversity circuit for subjecting a signal from the first antenna and a signal from the second antenna to diversity processing, wherein the diversity circuit is included in the receiving circuit or electrically connected to the receiving circuit.
In the configuration, it is possible to efficiently view a highly sensitive digital television broadcast from the signals received by the first antenna and the second antenna.
Further, in the portable radio of the present invention, the diversity circuit is a diversity circuit for performing diversity combination processing.
In the configuration, it is possible to efficiently view a highly sensitive digital television broadcast from the signals received by the first antenna and the second antenna.
In the portable radio of the present invention, the first impedance matching section and the first low noise amplifier are built into a single module.
In the configuration, the input impedance of the amplifier can be matched to a predetermined impedance by means of one module, so that designing and maintenance of the portable radio are facilitated.
In the portable radio of the present invention, the first antenna is a whip antenna projecting out of enclosures of the portable radio; and the second antenna is an antenna element built in the enclosures of the portable radio.
In the configuration, an impedance of the whip antenna serving as the first antenna is matched to a predetermined impedance, and the built-in antenna element serving as the second antenna is subjected to matching by means of a complex conjugate impedance. The second antenna can thereby be connected to the second low noise amplifier with a smaller loss. Further, the impedance of the first antenna is matched to a predetermined impedance, whereas the impedance of the second antenna is matched to the complex conjugate impedance. Thus, the impedance of the first antenna and the impedance of the second antenna can be made differ from each other, so that electromagnetic field coupling between the first antenna and the second antenna can be diminished. In this case, gain deterioration occurring between the antennas can be lessened, and a highly sensitive digital television broadcast can be viewed.
The portable radio of the present invention further includes a first circuit board placed in a first enclosure and a second circuit board placed in a second enclosure. The first antenna is a dipole antenna including at least a portion of the first circuit board and a portion of the second circuit board; and the second antenna is an antenna element built in the enclosures of the portable radio.
In the configuration, an impedance of the enclosure dipole antenna serving as the first antenna is matched to a predetermined impedance, and the built-in antenna element serving as the second antenna is subjected to matching by means of the complex conjugate impedance. The second antenna can thereby be connected to the second low noise amplifier with a smaller loss. Further, an impedance of the first antenna is matched to a predetermined impedance, whereas the impedance of the second antenna is matched to the complex conjugate impedance. Thus, the impedance of the first antenna and the impedance of the second antenna can be made differ from each other, so that electromagnetic field coupling between the first antenna and the second antenna can be diminished. In this case, gain deterioration occurring between the antennas can be lessened, and a highly sensitive digital television broadcast can be viewed.
Deterioration of an antenna gain attributable to electromagnetic field coupling between a plurality of antennas is improved, whereby viewing of a highly sensitive digital television broadcast becomes possible.
A portable radio of an embodiment of the present invention is a portable radio that is equipped with a television receiving feature having a diversity combination function and that has two antennas and two amplifiers inserted in two signal lines connecting the two antennas to a television tuner capable of performing diversity operation. Amplifiers exhibiting different input impedance characteristics at an operating band are used for the two amplifiers.
The DTV tuner module 15 has a receiving circuit that performs tuning processing for selecting a signal with a frequency band, which is employed in the DTV and which is included in the received signals from the first antenna 11 and the second antenna 13, and demodulation processing for demodulating the signal with the frequency band selected through tuning. A common receiving circuit can be provided for both the first antenna 11 and the second antenna 13, or an individual receiving circuit may also be provided separately for the first antenna 11 and the second antenna 13. The DTV tuner module can subject the signal from the first antenna 11 and the signal from the second antenna 13 to diversity processing, such as diversity combination or diversity selection. Diversity processing may be performed by the receiving circuit. Alternatively, when the receiving circuit is separately provided for each of the antennas, each of the diversity circuits electrically connected to the respective receiving circuits may also perform diversity processing.
Electrical connections in the portable radio of the embodiment shown in
In the portable radio of the present embodiment, the two antennas 11 and 13 are connected to the respective amplifiers 12 and 14 exhibiting different characteristics (different impedance characteristics of the operating band). Therefore, the two antennas 11 and 13 also exhibit the different terminal impedances Z1 (33) and Z2 (34) at a certain frequency. Since the terminal impedances differ from each other, the electromagnetic field coupling between the antennas 11 and 13 decreases, whereby gain deterioration attributable to the electromagnetic field coupling is improved. Highly sensitive digital television broadcasts can be viewed by improving gain deterioration of the antennas 11 and 13.
As mentioned above, the portable radio of the present embodiment has the first antenna 11; the second antenna 13; the first low noise amplifier 12 connected to the first antenna 11; the second low noise amplifier 14 connected to the second antenna 13; and the DTV tuner module 15 that is connected to the first low noise amplifier 12 and the second low noise amplifier 14 and that can perform diversity combination. In the operating frequency band of the DTV tuner module 15 capable of performing diversity combination, the input impedance of the first low noise amplifier 12 and the input impedance of the second low noise amplifier 14 differ from each other.
Therefore, the terminal impedances of the two antennas 11 and 13 differ from each other in the operating frequency band, and the electromagnetic field coupling between the antennas 11 and 13 decreases. Gain deterioration attributable to electromagnetic field coupling is eventually improved. Highly sensitive digital television broadcasts can be viewed by improving gain deterioration of the antennas 11 and 13.
The second 50-ohm impedance matching section 22 and the first amplifier 12 can be assembled into a single module; namely, packaged. The first amplifier 12 and the second amplifier 14 are made up of transistors, or the like, that are formed from silicon germanium or gallium arsenide. The impedance of these amplifiers sometimes vary from 50-ohm. As mentioned above, as a result of the impedance matching section and the amplifier being packaged into a module, the package becomes equivalent to an amplifier whose impedance is matched to 50-ohm.
The input impedance characteristic of the first amplifier 12 and the input impedance characteristic of the second amplifier 14 may be set so as to partially become equal to each other or entirely differ from each other at the operating band of the DTV. The input impedance characteristic of the second 50-ohm impedance matching section 22 that can be packaged and the input impedance characteristic of the first amplifier 12 (in other words, the input impedance characteristic of the second 50-ohm impedance matching section 22) and an input impedance characteristic of the second amplifier 14 are set so as to entirely differ from each other at the operating band of the DTV.
Electrical connections in the portable radio of the present embodiment shown in
When compared with a related art configuration 2 shown in
In
For instance, in the portable radio shown in
b) shows a Smith chart showing operation of the complex conjugate matching section; namely, operation for matching a certain impedance (falling in a domain designated by a solid line 44) to an impedance designated by a solid line 46. The impedance designated by the solid line 46 is a complex conjugate impedance responsive to an impedance falling in the domain designated by a dotted line 45. Namely, complex conjugate impedances fall in domains that are linearly symmetrical about a resistance axis (X=0) on the Smith chart.
In this case, even if the impedance falling within the domain designated by the solid line 44 has greatly differed from a value of 50 ohms, it may be the case where even a matching circuit entailing a little loss can perform matching, so long as the impedance is changed to a complex conjugate impedance designated by the solid line 46 that is responsive to the impedance falling in the domain designated by the dotted line 45.
For instance, in the portable radio shown in
When a wire for electrically connecting the first amplifier 12 to the DTV tuner module 15 is shorter than a predetermined standard, the portable radio of the present embodiment does not need to be provided with the third 50-ohm impedance matching section 23, and the matching section can also be omitted. In this case, an output terminal of the first amplifier 12 is connected directly to an input terminal of the DTV tuner module 15.
Moreover, the portable radios shown in
A type of the portable radio of the present embodiment is now described.
The impedance of the first antenna 11 and the impedance of the second antenna 13 are designed so as to become equal to a predetermined input impedance (e.g. 50 ohms) of the receiving circuit included in the DTV tuner module 15. For instance, in the case of an antenna that is used while projecting out of the portable radio, like a whip antenna, an input impedance of the antenna approximates to the predetermined input impedance. For this reason, in relation to a receiving line connected to the whip antenna (i.e., a line extending from the antenna to the DTV tuner module 15), a matching circuit entailing a little loss can be used even when an impedance matching section performs impedance matching at a stage immediately subsequent to the antenna.
As compared with the case of the whip antenna, when a built-in antenna element is used as an antenna, the input impedance of the antenna and the predetermined input impedance differ from each other by means of a loss, or the like, attributable to an enclosure of the portable radio itself. Therefore, in relation to the receiving line connected to the built-in antenna element, a matching circuit entailing a little loss can be used even when the complex conjugate matching section performs matching of a complex conjugate impedance at a stage immediately subsequent to the antenna.
Consequently, when the whip antenna and the built-in antenna element are used as antennas, the whip antenna is used as the first antenna 11, and the built-in antenna element is used as the second antenna 13. It is thereby possible to efficiently improve deterioration of an antenna gain and view a highly sensitive digital television broadcast.
When an enclosure dipole antenna that is a dipole antenna arranged in the enclosure of the portable radio is compared with the antenna element built in the enclosure of the portable radio, the enclosure dipole antenna is easy to gain an antenna gain. Therefore, when the enclosure dipole antenna and the built-in antenna element are used as antennas, the enclosure dipole antenna is used as the first antenna 11, and the built-in antenna element is used as the second antenna 13. It is thereby possible to efficiently improve deterioration of an antenna gain and view a highly sensitive digital television broadcast.
The present invention is not limited to the embodiments and can be implemented in various forms without departing the scope of the gist of the invention.
For example, the present embodiments have provided the descriptions about the receiving function to be included by reference to a digital television broadcast. However, the present invention is not limited to the digital television broadcast. The present invention is applicable to a function that is implemented by means of receiving a radio wave by use of a plurality of antennas.
Although the present invention has been described in detail by reference to the specific embodiments, it is manifest to the persons who are skilled in the art that the present invention be susceptible to various alterations or modifications without departing the spirit and scope of the present invention.
The present patent application is based on Japanese Patent Application No. 2008-123155 filed on May 9, 2008, the entire subject matter of which is incorporated herein by reference.
The present invention makes it possible to view a highly sensitive digital television broadcast by improving deterioration of an antenna gain attributable to electromagnetic field coupling between a plurality of antennas.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-123155 | May 2008 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2009/000751 | 2/20/2009 | WO | 00 | 11/9/2010 |
