JP2002141844A - Diversity receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a synthesizing effect equal to the maximum ratio synthesizing diversity receiving by suppressing expansion in device scale by receiving with linear operation and unnecessitating weighting based on an RSSI signal. SOLUTION: An intermediate frequency(IF) band signal resulting from converting the frequency of a received signal by a front end part 22a of a receiver 20A, is variably amplified by a variable gain amplifier 24a. An envelop detector 25a outputs a baseband signal by demodulating the IF band signal from the variable gain amplifier 24a, and an A/D converter 28a converts the baseband signal from a quadrature demodulator 27a to a digital signal and outputs it. A gain controller 26a outputs a gain control signal, which is lowered when a voltage value from the envelop detector 25a becomes large, so that the quadrature demodulator 27a and the A/D converter 28a can be operated with linear characteristics without being saturated. A receiving device 20B is operated similarly thereto as well. A gain control signal from one of gain controllers 26a and 26b of receiving device 20A or 20B on the side of the maximum received signal is selected by a selector circuit 30 and outputted to any one of variable gain amplifiers 24a and 24b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a maximum ratio combining diversity receiving system having two or more branches (receiving devices), and more particularly to a diversity receiving device for performing a receiving process based on linear characteristics.

[0002]

2. Description of the Related Art With the recent increase in the number of radio stations, narrowing of the frequency used has been studied in order to improve the frequency use efficiency. This narrowing of the band requires reception processing based on linear characteristics. Until now, for example, in the case of an A / D converter, a reception signal (I
F-band signal) level is set. Therefore, a configuration is generally used in which automatic gain control (AGC) is performed so that the input of the A / D converter falls within a required power level range.

[0003] Further, as a receiving process based on linear characteristics,
There is a diversity reception method. In the diversity receiving method, it is possible to improve the transmission level of the uplink and downlink communication channels of the line and the bit error rate (BER) in fading. As a diversity receiving method, a maximum ratio combining method for performing a weighting process in proportion to the amplitude of a received signal is known.

FIG. 7 is a block diagram showing an example of the configuration of a receiving apparatus using a conventional maximum ratio combining diversity receiving system.
Referring to FIG. 7, in the receiver 1A, the antenna 1a
Is received by the front-end unit 2a, amplified there, and frequency-converted into an IF band signal. The IF band signal is band-limited through a band-pass filter (BPF) 3a, and removes spurious components such as adjacent channels. The band-limited IF band signal is represented by I
The signal is amplified by the F amplifier 4a and then input to the phase shifter 5a.

The phase shifter 5a processes the control signals from the phase detector 6a so that the phases from all branches are the same. This processed signal is input to the multiplier 7a. The multiplier 7a weights the IF band signal with an RSSI signal obtained by envelope-detecting the received field strength signal from the received field strength (RSSI) signal generator 8a, and outputs the result to the combiner 8. These operations and the operation of the receiver 1B are the same.

The combiner 8 combines the outputs of the multipliers 7a and 7b, and outputs the output to the A / D converter 10 and the delay detector 1
1 to demodulate into a baseband signal and output.

[0007]

In such a conventional example, it is necessary to provide an RSSI signal generation circuit, a phase shifter and a phase detector, and the circuit scale is large. Therefore, there is a disadvantage that it is difficult to reduce the size of a receiver employing such a maximum ratio combining diversity reception system.

The present invention solves such a problem in the prior art. By receiving linear operation such as AGC and A / D conversion, weighting by an RSSI signal becomes unnecessary. , Phase shifter and phase detector become unnecessary,
It is an object of the present invention to provide a diversity receiving apparatus capable of obtaining a combining effect equivalent to that of a conventional maximum ratio combining diversity receiving system.

[0009]

According to the present invention, there is provided a diversity receiver having at least two receivers for performing maximum ratio combining diversity reception, wherein each of the receivers (receivers 20A and 20B) includes an antenna (antenna). 2
Reception processing means (front-end sections 22a, 22b) for frequency-converting the received signals from
b) and variable amplifying means (variable gain controllers 24a, 24a) for variably amplifying the intermediate frequency band signal from the reception processing means.
b), an envelope detection means (envelope detectors 25a, 25b) for outputting a voltage value corresponding to an output signal level from the reception processing means, and an intermediate frequency band signal from the variable gain amplifying means. Quadrature demodulation means for outputting band signals (quadrature demodulators 27a and 27b)
Digital signal converting means (A / A) for converting the baseband signal from the quadrature demodulating means into a digital signal and outputting the digital signal.
D converters 28a and 28b) and a gain control signal that decreases as the voltage value from the envelope detector increases so that the quadrature demodulator and the digital signal converter operate with linear characteristics without saturation. Gain control means (gain controllers 26a and 26b), and selects the gain control signal from the gain control means of the receiving apparatus in which the receiving signal in each receiving apparatus (receivers 20A and 20B) is the largest. It is characterized by comprising a selection means (selector 30) for outputting to the variable amplification means. According to this configuration, the amplitude difference of the output signal from the quadrature demodulation means is equal to the conventional R
In order to cope with the weighting by the SSI signal, an RSSI signal generation circuit, a phase shifter, and a phase detector for the RSSI signal are not required.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the diversity receiver according to the present invention will be described in detail with reference to the drawings. In the following description of the first to sixth embodiments, the same components are denoted by the same reference numerals.

FIG. 1 is a block diagram showing a configuration of a diversity receiver according to a first embodiment of the present invention. FIG.
, The diversity receiver of the first embodiment is an example of a configuration including two branches (receivers 20A and 20B).

The receiver 20A is provided with a front end unit 22a for amplifying a signal received from the antenna 21a and converting the signal into an IF band signal. Further, the receiver 2
0A includes a band-pass filter 23a for band-limiting an IF band signal and removing spurious components such as adjacent channels and outputting the IF band signal from the BPF 23a to a predetermined reception signal level based on a gain control signal. A variable gain amplifier 24a for controlling (performing positive gain control on the AGC / gain control signal) is provided.

Further, the receiver 20A includes an envelope detector 25a for outputting an RSSI signal (corresponding to the received electric field strength) obtained by envelope-detecting the IF band signal, and a variable gain controller 24a based on the RSSI signal from the envelope detector 25a. And a quadrature demodulator 27a for demodulating an IF band signal from the variable gain amplifier 24a to a baseband signal. Also,
An A / D converter 28 for converting the baseband signal from the quadrature demodulator 27a into a digital signal is provided in the receiver 20A.
A delay detector 29a for detecting a symbol point from the baseband signal from the A / D converter 28a is provided in addition to a. The configuration of the receiver 20A is the same as that of the receiver 20B. In the receiver 20B, the same reference numerals as those of the receiver 20A are denoted by “b” after the numerals.

In FIG. 1, a selection circuit 30 for selecting output signals (RSSI signals) from the envelope detectors 25a and 25b having large (maximum in a plurality of branches) received signals at the two receivers 20A and 20B, and a delay circuit A combiner 31 for combining and outputting output signals from the detectors 29a and 29b is provided.

Next, the operation of the first embodiment will be described. In the receiver 20A, a reception signal from the antenna 21a is input to the front end unit 22a, where the reception signal is amplified and frequency-converted into an IF band signal. IF
The band signal is band-limited by the BPF 23a, and outputs after removing spurious components such as adjacent channels. This BPF
The IF band signal from 23a is input to variable gain amplifier 24a. The variable gain amplifier 24a outputs the IF band signal to the quadrature demodulator 2 based on the gain control signal from the selection circuit 30.
7a and the appropriate input level of the A / D converter 28a.

The generation of the gain control signal in this case is based on the following operation. (I) The IF band signal is band-limited by the BPF 23a to remove spurious components such as adjacent channels. (Ii) The IF band signal from the BPF 23a is envelope-detected by the envelope detector 25a to obtain a voltage value (RSSI signal) corresponding to the level of the received electric field strength. (Iii) This voltage value has a time constant of an AGC loop gain adjustment and a polarity inversion and a sufficient response characteristic to the fading frequency, and is provided with a well-known loop filter (not shown). 26a. (Iv) The output signal (gain control signal) from the gain controller 26a decreases as the level of the received electric field strength (received signal) increases. (V) With the decreasing gain control signal, the variable gain amplifier 24a having the positive polarity characteristic is controlled to have a large gain. (Vi) The input levels of the quadrature demodulator 27a and the A / D converter 28a do not saturate even if the level of the received electric field strength (received signal) changes due to the gain control from (i) to (v). It operates with linear characteristics. For example, the operation is performed within the dynamic range.

The operation of the receiver 20A and the operation of the receiver 20B operating in this manner are the same. Here, the variable gain amplifier 2
The gain control signals input to 4a and 24b are always minimum,
That is, the output from the receiver having the highest received signal level (here, one of the receivers 20A and 20B) is selected by the selection circuit 3.
0 is selected. Since the selected gain control signal is input to the variable gain amplifiers 24a and 24b of all receivers (here, both the receivers 20 and 20B), a baseband signal having an amplitude value corresponding to the received signal level is quadrature demodulated. Container 27
a and 27b.

The amplitude difference between the output signals from the quadrature demodulators 27a and 27b corresponds to the weighting by the RSSI signal. Therefore, by combining the output signals from the delay detectors 29a and 29b with the combiner 31, a combining effect similar to that of the conventional maximum ratio combining diversity receiving method of weighting with the RSSI signal can be obtained.

In addition to obtaining the synthesizing effect,
This synthesis is performed by the delay detector 29a by the A / D converter 28.
Since the detection is performed at the symbol point from the baseband signal from a, the combining can be performed by the combiner 31 without performing the phase adjustment by the phase shifter described in the conventional example. As a result, an increase in the scale of the device can be suppressed.

FIG. 2 is a block diagram showing a configuration in the second embodiment. In FIG. 2, the diversity receiver according to the second embodiment is a configuration example including two branches (receivers 30A and 30B) similar to the first embodiment. The receivers 30A and 30B include a variable attenuator 32a (32) instead of the variable gain amplifier 24a (24b) in the first embodiment.
b) is provided.

Other configurations are similar to those of the receiver 2 of the first embodiment.
It has the same configuration as that of 0A (20B). That is, the antenna 21a (21b) and the front end 22a (22
b), band-pass filter 23a (23b), envelope detector 25a (25b), gain controller 26a (26)
b), a quadrature demodulator 27a (27a), an A / D converter 28a (28a), a delay detector 29a (29b), a selector 30, and a combiner 31.

Next, the operation of the second embodiment will be described. The receiver 30A (30B) has a variable attenuator 32a (3
Operations other than 2b) are the same as those in the first embodiment, and a duplicate description will be omitted. The level of the gain control signal from gain controller 26a (26b) corresponds to the level of the received signal. As the level of the received signal increases, the level of the gain control signal also increases. As a result, the variable attenuator 32a (32b) having the characteristic of the positive polarity increases the attenuation when the level of the received signal increases, and decreases when the level of the received signal decreases.

As a result, the baseband signals having the amplitude values corresponding to the received signal levels are output from the quadrature demodulators 27a and 27b, and the combining effect similar to that of the conventional maximum ratio combining diversity receiving system as in the first embodiment. Is obtained. Furthermore, it is possible to perform the synthesis by the synthesizer 31 without performing the phase adjustment by the phase shifter described in the conventional example, thereby suppressing an increase in the device scale.

FIG. 3 is a block diagram showing a configuration according to the third embodiment. In FIG. 3, the diversity receiver according to the third embodiment is a configuration example including the same two branches (receivers 40A and 40B) as in the first embodiment. In FIG. 1, a receiver 40A (40B) is basically the same as the configuration of the first embodiment. That is, the receiver 40A (4
0B) includes an antenna 21a (21b), a front end unit 22a (22b), and a band-pass filter 23a (23
b), variable gain amplifier 24a (24b), envelope detector 25a (25b), gain controller 26a (26
b), a quadrature demodulator 27a (27a), an A / D converter 28a (28a), a delay detector 29a (29b), a selector 30, and a combiner 31.

In the third embodiment, the input side of the envelope detector 25a (25b) is connected to the variable gain amplifier 24a.
(24b) is connected to the output side. The output of the selector 30 is connected to the control terminal of the variable gain amplifier 24a (24b). This gain control is a closed loop method. The first embodiment is an open-loop system.

Next, the operation of the third embodiment will be described. The basic operation of the receiver 40A (40B) is as follows.
This is the same as the first embodiment, and a duplicate description will be omitted.
The level of the gain control signal from the gain controller 26a (26b) decreases as the level of the received signal increases. As a result, the variable gain amplifier 24a (24b) having positive polarity characteristics operates so that the amplification gain increases when the level of the received signal decreases, and decreases when the level of the received signal increases. Works like that.

As a result, the baseband signals having the amplitude values corresponding to the received signal levels are output from the quadrature demodulators 27a and 27b, and the combining effect similar to that of the conventional maximum ratio combining diversity receiving system as in the first embodiment. Is obtained. Furthermore, it is possible to perform the synthesis by the synthesizer 31 without performing the phase adjustment by the phase shifter described in the conventional example, thereby suppressing an increase in the device scale.

FIG. 4 is a block diagram showing a configuration in the fourth embodiment. In FIG. 4, the diversity receiver according to the fourth embodiment is a configuration example using the same two branches (receivers 50A and 50B) as in the first embodiment. In FIG. 4, a receiver 50A (50B) has the same configuration as in the second embodiment. That is, the antenna 21a (21
b), front-end section 22a (22b), band-pass filter 23a (23b), envelope detector 25a
(25b), gain controller 26a (26b), quadrature demodulator 27a (27a), A / D converter 28a (28
a), a delay detector 29a (29b), a selector 30, a combiner 31, and a variable attenuator 32a (32b).

In the fourth embodiment, the input side of the envelope detector 25a (25b) is connected to the variable gain amplifier 24a.
(24b) is connected to the output side. The output of the selector 30 is connected to the control terminal of the variable gain amplifier 24a (24b). Gain control is a closed loop method.

Next, the operation of the fourth embodiment will be described. The receiver 50A (50B) is the same as in the second embodiment, and a duplicate description will be omitted. Gain controller 26a
The level of the gain control signal from (26b) corresponds to the level of the received signal. When the level of the received signal increases,
The level of the gain control signal also increases. As a result, the variable attenuator 32a (32b) having the characteristic of the positive polarity increases the attenuation when the level of the received signal increases, and decreases when the level of the received signal decreases.

As a result, the baseband signal having the amplitude value corresponding to the received signal level is output from the quadrature demodulators 27a and 27b, and the combining effect similar to that of the conventional maximum ratio combining diversity receiving system as in the first embodiment. Is obtained. Furthermore, it is possible to perform the synthesis by the synthesizer 31 without performing the phase adjustment by the phase shifter described in the conventional example, thereby suppressing an increase in the device scale.

FIG. 5 is a block diagram showing a configuration in the fifth embodiment. In FIG. 5, the diversity receiver according to the fifth embodiment is an example of a configuration including two branches (receivers 60A and 60B) similar to the first embodiment.

In FIG. 1, receiver 60A (60B)
Is basically the same as the configuration of the first embodiment. That is, the receiver 60A (60B) receives the antenna 21a (21
b), front-end section 22a (22b), band-pass filter 23a (23b), variable gain amplifier 24a (24
b), envelope detector 25a (25b), gain controller 26a (26b), quadrature demodulator 27a (27a), A
/ D converter 28a (28a), delay detector 29a
(29b), a selector 30, and a synthesizer 31.

In the fifth embodiment, the input side of the envelope detector 25a (25b) is connected to the quadrature demodulator 27a (2b).
7a) is connected to the output side. The output of the selector 30 is connected to the control terminal of the variable gain amplifier 24a (24b). This gain control is a closed loop method.

Next, the operation of the fifth embodiment will be described. The basic operation of the receiver 60A (60B) is as follows.
This is the same as the first embodiment, and a duplicate description will be omitted.
The level of the gain control signal from the gain controller 26a (26b) decreases as the level of the received signal increases. As a result, the variable gain amplifier 24a (24b) having positive polarity characteristics operates so that the amplification gain increases when the level of the received signal decreases, and decreases when the level of the received signal increases. Works like that.

As a result, the baseband signals having the amplitude values corresponding to the received signal levels are output from the quadrature demodulators 27a and 27b, and the combining effect similar to that of the conventional maximum ratio combining diversity receiving system as in the first embodiment. Is obtained. Furthermore, it is possible to perform the synthesis by the synthesizer 31 without performing the phase adjustment by the phase shifter described in the conventional example, thereby suppressing an increase in the device scale.

FIG. 6 is a block diagram showing the configuration of the sixth embodiment. In FIG. 6, the diversity receiver according to the sixth embodiment is a configuration example including two branches (receivers 60A and 60B) similar to the first embodiment. In FIG. 6, a receiver 60A (60B) has the same configuration as in the fourth embodiment. That is, the antenna 21a (21
b), front-end section 22a (22b), band-pass filter 23a (23b), envelope detector 25a
(25b), gain controller 26a (26b), quadrature demodulator 27a (27a), A / D converter 28a (28
a), a delay detector 29a (29b), a selector 30, a combiner 31, and a variable attenuator 32a (32b).

In the sixth embodiment, the input side of the envelope detector 25a (25b) is connected to the quadrature demodulator 27a (2b).
7a) is connected to the output side. The output of the selector 30 is connected to the control terminal of the variable gain amplifier 24a (24b). Gain control is a closed loop method.

Next, the operation of the sixth embodiment will be described. The receiver 60A (60B) is the same as in the fourth embodiment, and a duplicate description will be omitted. Gain controller 26a (2
The level of the gain control signal from 6b) corresponds to the level of the received signal. As the level of the received signal increases, the level of the gain control signal also increases. As a result, the variable attenuator 32a (32b) having the characteristic of the positive polarity increases the attenuation when the level of the received signal increases, and decreases when the level of the received signal decreases.

As a result, the baseband signals having the amplitude values corresponding to the received signal levels are output from the quadrature demodulators 27a and 27b, and the combining effect similar to that of the conventional maximum ratio combining diversity receiving system is used as in the first embodiment. Is obtained. Furthermore, it is possible to perform the synthesis by the synthesizer 31 without performing the phase adjustment by the phase shifter described in the conventional example, thereby suppressing an increase in the device scale.

[0041]

As is apparent from the above description, according to the diversity receiver of the present invention, weighting by the RSSI signal becomes unnecessary by linear operation reception such as AGC and A / D conversion, and the RSSI signal generation circuit In addition, there is an effect that a synthesizing effect equivalent to that of a conventional maximum ratio combining diversity receiving system can be obtained without providing a phase shifter, a phase detector, or the like and suppressing an increase in the device scale.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a diversity receiver according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration according to a second embodiment.

FIG. 3 is a block diagram illustrating a configuration according to a third embodiment.

FIG. 4 is a block diagram illustrating a configuration according to a fourth embodiment.

FIG. 5 is a block diagram illustrating a configuration according to a fifth embodiment.

FIG. 6 is a block diagram illustrating a configuration according to a sixth embodiment.

FIG. 7 is a block diagram illustrating a configuration of a conventional diversity receiving apparatus.

[Explanation of symbols]

 20A, 20B to 60A, 60B Receiver 21a, 21b Antenna 22a, 22b Front end unit 23a, 23b Bandpass filter 24a, 24b Variable gain amplifier 25a, 25b Envelope detector 26a, 26b Gain controller 27a, 27b Quadrature demodulator 28a , 28b A / D converter 29a, 29b Delay detector 30 Selection circuit 31 Combiner 32a (32b) Variable attenuator

Claims (7)

[Claims] 1. A diversity receiving apparatus comprising at least two receiving apparatuses and performing maximum ratio combining diversity reception, wherein each of the receiving apparatuses performs frequency conversion of a signal received from an antenna into an intermediate frequency band, A variable amplifying means for variably amplifying an intermediate frequency band signal from the reception processing means; an envelope detection means for outputting a voltage value corresponding to an output signal level from the reception processing means; and an intermediate frequency from the variable gain amplifying means. Quadrature demodulation means for demodulating a band signal and outputting a baseband signal; digital signal conversion means for converting a baseband signal from the quadrature demodulation means into a digital signal and outputting the digital signal; quadrature demodulation means and the digital signal conversion The voltage value from the envelope detection means is large so that the means operates with linear characteristics without saturation. Gain control means for outputting a gain control signal that decreases as the frequency increases.The received signal in each receiving apparatus selects a gain control signal from the gain control means of the receiving apparatus on the maximum side and outputs the selected signal to the variable amplifying means. A diversity receiving device comprising: 2. A variable attenuating means is provided in place of said variable amplifying means, and said gain control means is said envelope detecting means for operating said quadrature demodulating means and digital signal converting means with a linear characteristic without being saturated. A gain control signal corresponding to the voltage value from is output to the variable attenuating means, and when the received signal level is large, the amount of attenuation in the variable attenuating means is controlled to be large, and when the level of the received signal is small, 2. The diversity receiver according to claim 1, wherein the amount of attenuation in said variable attenuation means is controlled to be small. 3. An output signal from the variable amplification means is input to the envelope detection means, and the gain control means operates the quadrature demodulation means and the digital signal conversion means with linear characteristics without being saturated. 2. The diversity receiver according to claim 1, wherein a gain control signal that decreases as the voltage value from the envelope detection means increases. 4. A variable attenuating means is provided in place of said variable amplifying means, an output signal of said variable attenuating means is input to said envelope detecting means, and said gain controlling means is said quadrature demodulating means and digital signal converting means. Outputs a gain control signal corresponding to the voltage value from the envelope detecting means to the variable attenuating means for operating with linear characteristics without saturation, and when the received signal level is large, the variable attenuating means 2. The diversity receiver according to claim 1, wherein the amount of attenuation is controlled to be large, and the amount of attenuation by said variable attenuating means is controlled to be small when the level of a received signal is small. 5. An output signal from the quadrature demodulation means is input to the envelope detection means, and the gain control means operates with linear characteristics without the quadrature demodulation means and the digital signal conversion means being saturated. 2. The diversity receiver according to claim 1, wherein a gain control signal that decreases as the voltage value from the envelope detector increases increases. 6. A variable attenuating means is provided in place of said variable amplifying means, an output signal of said quadrature demodulation means is input to said envelope detection means, and said gain control means is said quadrature demodulation means and digital signal conversion means. Outputs a gain control signal corresponding to the voltage value from the envelope detecting means to the variable attenuating means for operating with linear characteristics without saturation, and when the received signal level is large, the variable attenuating means 2. The diversity receiver according to claim 1, wherein the amount of attenuation is controlled to be large, and the amount of attenuation by said variable attenuating means is controlled to be small when the level of a received signal is small. 7. The receiving apparatus according to claim 1, further comprising a band-limiting filter for band-limiting the intermediate frequency band signal to remove at least adjacent channel spurious components. Any one
The diversity receiver according to the item.