JP4357732B2 - Diversity receiver - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a maximum ratio combining diversity reception system including two or more branches (reception apparatuses), and more particularly to a diversity reception apparatus that performs reception processing based on linear characteristics.
[0002]
[Prior art]
With the recent increase in radio stations, in order to improve the frequency utilization efficiency, the use of a narrower frequency band is being studied. This narrowing of the band requires reception processing based on linear characteristics. As a reception process using a linear characteristic for narrowing the band, for example, in an A / D converter, a reception signal (IF band signal) level is set within a dynamic range on the input side. For this reason, a configuration in which automatic gain control (AGC) is performed so that the input of the A / D converter is within the required power level range is common.
[0003]
In addition, as a reception process using linear characteristics, there is a diversity reception method. In the diversity reception system, it is possible to improve the transmission level of the uplink / downlink communication channel of the line and the bit error rate (BER) in fading. As a diversity reception method, a maximum ratio combining method that performs weighting processing in proportion to the amplitude of a received signal is known.
[0004]
FIG. 7 is a block diagram showing a configuration example of a receiving apparatus according to a conventional maximum ratio combining diversity receiving system.
Referring to FIG. 7, in the receiver 1A, the reception signal received by the antenna 1a is input to the front end unit 2a, amplified there, and then 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 amplified by the IF amplifier 4a and then input to the phase shifter 5a.
[0005]
The phase shifter 5a performs processing so that the phases from all the branches become the same phase by the control signal from the phase detector 6a. This processed signal is input to the multiplier 7a. The multiplier 7a weights the IF band signal with the RSSI signal obtained by envelope detection of the received electric field strength signal from the received electric 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.
[0006]
The synthesizer 8 synthesizes the outputs of the multipliers 7a and 7b, demodulates the output into a baseband signal through the A / D converter 10 and the delay detector 11, and outputs the baseband signal.
[0007]
[Problems to be solved by the invention]
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 drawback that it is difficult to reduce the size of a receiver that employs such a maximum ratio combining diversity reception system.
[0008]
The present invention solves such a problem in the conventional technique, and weighting by an RSSI signal becomes unnecessary by receiving linear operation such as AGC or A / D conversion. For example, an RSSI signal generation circuit, a phase shifter, etc. In addition, an object of the present invention is to provide a diversity receiver that eliminates the need for a phase detector and suppresses an increase in the device scale, and that can achieve a combining effect equivalent to that of a conventional maximum ratio combining diversity receiver.
[0009]
[Means for Solving the Problems]
The present invention is a diversity receiver that includes at least two receivers and performs maximum ratio combining diversity reception. Each receiver (receiver 20A, 20B) receives a received signal from an antenna (antenna 21a, 21b). Reception processing means (front end units 22a and 22b) for frequency conversion to an intermediate frequency band, variable amplification means (variable gain controllers 24a and 24b) for variably amplifying intermediate frequency band signals from the reception processing means, and the reception Envelope detection means (envelope detectors 25a and 25b) for outputting a voltage value corresponding to the output signal level from the processing means, and orthogonal to demodulate the intermediate frequency band signal from the variable gain amplification means and output a baseband signal Demodulating means (orthogonal demodulators 27a and 27b) and a baseband signal from the orthogonal demodulating means Digital signal conversion means (A / D converters 28a and 28b) for converting the signal into a clock signal and the envelope detection means so that the quadrature demodulation means and the digital signal conversion means operate with linear characteristics without saturation. Gain control means (gain controllers 26a, 26b) for outputting a gain control signal that decreases as the voltage value from the receiver increases, and the reception signal at each receiving device (receiver 20A, 20B) is the reception signal on the maximum side. The apparatus further comprises selection means (selector 30) for selecting a gain control signal from the gain control means of the apparatus and outputting it to the variable amplification means. According to this configuration, the amplitude difference of the output signals from the quadrature demodulating means corresponds to the conventional weighting by the RSSI signal, so that the RSSI signal generation circuit, the phase shifter, and the phase detector related to the RSSI signal are not required.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the diversity receiver of 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.
[0011]
FIG. 1 is a block diagram showing the configuration of the first embodiment of the diversity receiver of the present invention. In FIG. 1, the diversity receiver according to the first embodiment is a configuration example by two branches (receivers 20A and 20B).
[0012]
The receiver 20A is provided with a front-end unit 22a that amplifies a received signal from the antenna 21a and converts it into an IF band signal. Further, the receiver 20A limits the band of the IF band signal, removes a spurious component such as an adjacent channel and outputs the band-pass filter 23a, and outputs the IF band signal from the BPF 23a to a predetermined reception signal level as a gain control signal. A variable gain amplifier 24a that performs gain control based on the above (performs positive gain control on the AGC / gain control signal) is provided.
[0013]
Further, the receiver 20A includes an envelope detector 25a that outputs an RSSI signal (corresponding to the received electric field strength) obtained by envelope detection of the IF band signal, and gain control of the variable gain controller 24a by the RSSI signal from the envelope detector 25a. A gain controller 26a having a loop filter for performing the above is provided, and an orthogonal demodulator 27a for demodulating the IF band signal from the variable gain amplifier 24a into a baseband signal is provided. The receiver 20A includes a delay detector 29a that detects a symbol point from the baseband signal from the A / D converter 28a, as well as an A / D converter 28a that converts the baseband signal from the quadrature demodulator 27a into a digital signal. Is provided. The receiver 20A has the same configuration as the receiver 20B. In the receiver 20B, “b” is appended to the reference numerals of the same parts as those of the receiver 20A.
[0014]
In FIG. 1, a selection circuit 30 for selecting an output signal (RSSI signal) from envelope detectors 25a and 25b having large received signals at two receivers 20A and 20B (maximum in a plurality of branches), and a delay detector 29a. , 29b, a synthesizer 31 for synthesizing and outputting the output signals is provided.
[0015]
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. The IF band signal is band-limited by the BPF 23a, and spurious components such as adjacent channels are removed and output. The IF band signal from the BPF 23a is input to the variable gain amplifier 24a. The variable gain amplifier 24a controls the IF band signal to an appropriate input level of each of the quadrature demodulator 27a and the A / D converter 28a based on the gain control signal from the selection circuit 30.
[0016]
In this case, the gain control signal is generated by the following operation.
(I) The band of the IF band signal is limited by the BPF 23a, and spurious components such as adjacent channels are removed.
(Ii) The envelope detection is performed on the IF band signal from the BPF 23a by the envelope detector 25a to obtain a voltage value (RSSI signal) corresponding to the level of the received electric field intensity.
(Iii) This voltage value has the time constant of the response characteristic sufficient for the fading frequency, which reverses the adjustment and polarity of the AGC loop gain, 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 this decreasing gain control signal, the variable gain amplifier 24a having the positive polarity characteristic is controlled to a large gain.
(Vi) The input levels of the quadrature demodulator 27a and the A / D converter 28a are not saturated even if the level of the received electric field intensity (received signal) changes by the gain control from (i) to (v). Operates with linear characteristics. For example, it is operated within the dynamic range.
[0017]
The operations of the receiver 20A and the receiver 20B that operate in this way are the same. Here, the gain control signal input to the variable gain amplifiers 24a and 24b is always the minimum, that is, the selection circuit 30 selects the output from the receiver having the maximum received signal level (here, one of the receivers 20A and 20B). select. Since the selected gain control signal is input to the variable gain amplifiers 24a and 24b of all the receivers (in this case, both the receivers 20 and 20B), the baseband signal having an amplitude value corresponding to the received signal level is quadrature demodulated. Are output from the devices 27a and 27b.
[0018]
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 in which weighting is performed with the RSSI signal can be obtained.
[0019]
In addition, this combination effect is obtained, and the delay detector 29a detects this combination at the symbol point from the baseband signal from the A / D converter 28a, so that the phase adjustment by the phase shifter described in the conventional example is performed. Without being performed, the synthesizer 31 can synthesize. As a result, an increase in device scale can be suppressed.
[0020]
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 by two branches (receivers 30A and 30B) similar to those of the first embodiment. The receivers 30A and 30B are provided with a variable attenuator 32a (32b) instead of the variable gain amplifier 24a (24b) in the first embodiment.
[0021]
Other configurations are the same as those of the receiver 20A (20B) of the first embodiment. That is, antenna 21a (21b), front end 22a (22b), band pass filter 23a (23b), envelope detector 25a (25b), gain controller 26a (26b), quadrature demodulator 27a (27a), A / It comprises a D converter 28 a (28 a), a delay detector 29 a (29 b), a selector 30, and a combiner 31.
[0022]
Next, the operation of the second embodiment will be described. The operation of the receiver 30A (30B) other than the variable attenuator 32a (32b) is the same as that of the first embodiment, and redundant description is omitted. The level of the gain control signal from the 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 positive polarity characteristic increases the amount of attenuation when the level of the received signal increases, and decreases when the level of the received signal decreases.
[0023]
As a result, a baseband signal having an amplitude value corresponding to the received signal level is output from the quadrature demodulators 27a and 27b, and the same combining effect as that of the conventional maximum ratio combining diversity receiving method is obtained as in the first embodiment. . Furthermore, it is possible to synthesize by the synthesizer 31 without performing the phase adjustment by the phase shifter described with reference to the conventional example, and the increase in the scale of the apparatus can be suppressed.
[0024]
FIG. 3 is a block diagram showing a configuration in the third embodiment. In FIG. 3, the diversity receiver according to the third embodiment is a configuration example by two branches (receivers 40A and 40B) similar to those of 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 (40B) includes an antenna 21a (21b), a front end unit 22a (22b), a band pass filter 23a (23b), a variable gain amplifier 24a (24b), an envelope detector 25a (25b), and gain control. 26a (26b), quadrature demodulator 27a (27a), A / D converter 28a (28a), delay detector 29a (29b), selector 30, and synthesizer 31.
[0025]
In the third embodiment, the input side of the envelope detector 25a (25b) is connected to the output side of the variable gain amplifier 24a (24b). 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 system. The first embodiment is an open loop method.
[0026]
Next, the operation of the third embodiment will be described. The basic operation of the receiver 40A (40B) is the same as that of the first embodiment, and redundant description is 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 the positive polarity characteristic operates so that the amplification gain increases when the level of the reception signal decreases, and decreases when the level of the reception signal increases. To work.
[0027]
As a result, a baseband signal having an amplitude value corresponding to the received signal level is output from the quadrature demodulators 27a and 27b, and the same combining effect as that of the conventional maximum ratio combining diversity receiving method is obtained as in the first embodiment. . Furthermore, it is possible to synthesize by the synthesizer 31 without performing the phase adjustment by the phase shifter described with reference to the conventional example, and the increase in the scale of the apparatus can be suppressed.
[0028]
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 by two branches (receivers 50A and 50B) similar to those of the first embodiment. In FIG. 4, the receiver 50A (50B) has the same configuration as that of the second embodiment. That is, antenna 21a (21b), front end 22a (22b), band pass filter 23a (23b), envelope detector 25a (25b), gain controller 26a (26b), quadrature demodulator 27a (27a), A / It comprises a D converter 28a (28a), a delay detector 29a (29b), a selector 30, a combiner 31, and a variable attenuator 32a (32b).
[0029]
In the fourth embodiment, the input side of the envelope detector 25a (25b) is connected to the output side of the variable gain amplifier 24a (24b). 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 system.
[0030]
Next, the operation of the fourth embodiment will be described. The receiver 50A (50B) is the same as that of the second embodiment, and redundant description is omitted. The level of the gain control signal from the 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 positive polarity characteristic increases the amount of attenuation when the level of the received signal increases, and decreases when the level of the received signal decreases.
[0031]
As a result, a baseband signal having an amplitude value corresponding to the received signal level is output from the quadrature demodulators 27a and 27b, and the same combining effect as that of the conventional maximum ratio combining diversity receiving method is obtained as in the first embodiment. . Furthermore, it is possible to synthesize by the synthesizer 31 without performing the phase adjustment by the phase shifter described with reference to the conventional example, and the increase in the scale of the apparatus can be suppressed.
[0032]
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 a configuration example including two branches (receivers 60A and 60B) similar to those in the first embodiment.
[0033]
In FIG. 1, a receiver 60A (60B) is basically the same as the configuration of the first embodiment. That is, the receiver 60A (60B) includes an antenna 21a (21b), a front end unit 22a (22b), a band pass filter 23a (23b), a variable gain amplifier 24a (24b), an envelope detector 25a (25b), a gain. It comprises a controller 26a (26b), a quadrature demodulator 27a (27a), an A / D converter 28a (28a), a delay detector 29a (29b), a selector 30, and a combiner 31.
[0034]
In the fifth embodiment, the input side of the envelope detector 25a (25b) is connected to the output side of the quadrature demodulator 27a (27a). 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 system.
[0035]
Next, the operation of the fifth embodiment will be described. The basic operation of the receiver 60A (60B) is the same as that of the first embodiment, and a duplicate description is 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 the positive polarity characteristic operates so that the amplification gain increases when the level of the reception signal decreases, and decreases when the level of the reception signal increases. To work.
[0036]
As a result, a baseband signal having an amplitude value corresponding to the received signal level is output from the quadrature demodulators 27a and 27b, and the same combining effect as that of the conventional maximum ratio combining diversity receiving method is obtained as in the first embodiment. . Furthermore, it is possible to synthesize by the synthesizer 31 without performing the phase adjustment by the phase shifter described with reference to the conventional example, and the increase in the scale of the apparatus can be suppressed.
[0037]
FIG. 6 is a block diagram showing a configuration in the sixth embodiment. In FIG. 6, the diversity receiver according to the sixth embodiment is a configuration example using two branches (receivers 60 </ b> A and 60 </ b> B) similar to those in the first embodiment. In FIG. 6, the receiver 60A (60B) has the same configuration as that of the fourth embodiment. That is, antenna 21a (21b), front end 22a (22b), band pass filter 23a (23b), envelope detector 25a (25b), gain controller 26a (26b), quadrature demodulator 27a (27a), A / It comprises a D converter 28a (28a), a delay detector 29a (29b), a selector 30, a combiner 31, and a variable attenuator 32a (32b).
[0038]
In the sixth embodiment, the input side of the envelope detector 25a (25b) is connected to the output side of the quadrature demodulator 27a (27a). 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 system.
[0039]
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 is omitted. The level of the gain control signal from the 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 positive polarity characteristic increases the amount of attenuation when the level of the received signal increases, and decreases when the level of the received signal decreases.
[0040]
As a result, a baseband signal having an amplitude value corresponding to the received signal level is output from the quadrature demodulators 27a and 27b, and the same combining effect as that of the conventional maximum ratio combining diversity receiving method is obtained as in the first embodiment. . Furthermore, it is possible to synthesize by the synthesizer 31 without performing the phase adjustment by the phase shifter described with reference to the conventional example, and the increase in the scale of the apparatus can be suppressed.
[0041]
【The invention's effect】
As is clear from the above description, according to the diversity receiver of the present invention, weighting by the RSSI signal is not required by linear operation reception such as AGC or A / D conversion, and the RSSI signal generation circuit, the phase shifter, and the phase There is an effect that a synthesizing effect equivalent to that of the conventional maximum ratio combining diversity receiving system can be obtained by suppressing an increase in apparatus scale without providing a detector or the like.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration in a first embodiment of a diversity receiver of the present invention.
FIG. 2 is a block diagram showing a configuration in a second embodiment.
FIG. 3 is a block diagram showing a configuration in a third embodiment.
FIG. 4 is a block diagram showing a configuration in a fourth embodiment.
FIG. 5 is a block diagram showing a configuration in a fifth embodiment.
FIG. 6 is a block diagram showing a configuration in a sixth embodiment.
FIG. 7 is a block diagram showing a configuration of a conventional diversity receiver.
[Explanation of symbols]
20A, 20B to 60A, 60B Receivers 21a, 21b Antennas 22a, 22b Front end units 23a, 23b Bandpass filters 24a, 24b Variable gain amplifiers 25a, 25b Envelope detectors 26a, 26b Gain controllers 27a, 27b Quadrature demodulator 28a 28b A / D converters 29a, 29b Delay detector 30 Select circuit 31 Synthesizer 32a (32b) Variable attenuator

Claims (7)

In the diversity receiving device that includes at least two receiving devices and performs the maximum ratio combining diversity reception, each receiving device,
A reception processing means for converting the received signal from the antenna into an intermediate frequency band;
Variable amplification means for variably amplifying the intermediate frequency band signal from the reception processing means;
Envelope detection means for outputting a voltage value corresponding to an output signal level from the reception processing means;
And quadrature demodulating means for outputting a base band signal by demodulating the intermediate frequency band signal from the friendly Henzo width means,
Digital signal conversion means for converting the baseband signal from the quadrature demodulation means into a digital signal and outputting the digital signal;
Gain control means for outputting a gain control signal that decreases as the voltage value from the envelope detection means increases so that the quadrature demodulation means and the digital signal conversion means operate with linear characteristics without being saturated, and
Selecting means for selecting the gain control signal from the gain control means of the receiving device on the maximum side of the received signal in each receiving device and outputting the selected signal to the variable amplifying device ;
A diversity receiving apparatus characterized in that a combined signal is obtained by adaptively changing a combining ratio according to a level difference of a digital baseband signal output from a digital signal converting means of the receiving apparatus. A variable attenuation means is provided instead of the variable amplification means,
The gain control means outputs to the variable attenuation means a gain control signal corresponding to a voltage value from the envelope detection means for operating the linear demodulation means and the digital signal conversion means without saturation. The amount of attenuation in the variable attenuation means is controlled to be large when the received signal level is high, and the amount of attenuation in the variable attenuation means is controlled to be small when the level of the received signal is small. The diversity receiver according to 1. An output signal from the variable amplification means is input to the envelope detection means,
The gain control means outputs a gain control signal that decreases as the voltage value from the envelope detection means increases so that the quadrature demodulation means and the digital signal conversion means operate with linear characteristics without being saturated. The diversity receiver according to claim 1, wherein: A variable attenuation means is provided instead of the variable amplification means,
The output signal of the variable attenuation means is input to the envelope detection means,
The gain control means outputs, to the variable attenuation means, a gain control signal corresponding to the voltage value from the envelope detection means for allowing the quadrature demodulation means and the digital signal conversion means to operate in a linear characteristic without being saturated. The attenuation amount in the variable attenuation means is controlled to be large when the reception signal level is high, and the attenuation amount in the variable attenuation means is controlled to be small when the reception signal level is low. The diversity receiver according to Item 1. An output signal from the quadrature demodulation means is input to the envelope detection means, and
The gain control means outputs a gain control signal that decreases as the voltage value from the envelope detection means increases so that the quadrature demodulation means and the digital signal conversion means operate with linear characteristics without being saturated. The diversity receiver according to claim 1, wherein: A variable attenuation means is provided instead of the variable amplification means,
An output signal of the quadrature demodulation means is input to the envelope detection means,
The gain control means outputs, to the variable attenuation means, a gain control signal corresponding to the voltage value from the envelope detection means for allowing the quadrature demodulation means and the digital signal conversion means to operate in a linear characteristic without being saturated. The attenuation amount in the variable attenuation means is controlled to be large when the reception signal level is high, and the attenuation amount in the variable attenuation means is controlled to be small when the reception signal level is low. The diversity receiver according to Item 1. As the next stage of the reception processing means,
The diversity receiving apparatus according to claim 1, further comprising a band limiting filter that limits a band of the intermediate frequency band signal and removes at least an adjacent channel spurious component.

Images