JPH1041867A - Diversity receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide with simple configuration a diversity receiver in which a cost is reduced. SOLUTION: Signals received by antennas 1 and 2 outputs values in proportion to the logarithm of a baseband signal and a reception signal field strength indicator (RSSI) in receiving parts 3 and 4. The baseband signals from the receiving parts 3 and 4 are digitized through an A/D converter 5. Weighting is selected by weighting tables 23 and 24, is accordance with RSSI, weighting is executed in the baseband signals by bit shifters 25 and 26 and, then they are synthesized and outputted. A weighting part consists only of an adder 10 and a bit shift 25, so that configuration is simplified and cost is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diversity receiver used for wireless communication and the like.

[0002]

2. Description of the Related Art A diversity receiver is an effective means for removing the effects of fading from a signal received by a receiver. The general method includes a post-detection maximum ratio combining diversity scheme in which baseband signals from a plurality of receiving sections are weighted by the square of the received field strength at each receiving section, combined and decoded, and , A post-detection selection diversity system that selects a signal having the highest received electric field strength from among the received signals and performs decoding. At present, it is known that the maximum ratio combining diversity scheme after detection is superior to the selection diversity scheme after detection.

FIG. 7 is a block diagram of a conventional maximum ratio combining diversity receiver after detection. In FIG. 7, the signals received by the antennas 1 and 2 are output by the receiving units 3 and 4 as RSSI signals proportional to the logarithmic (dB) value of the baseband signal and the received electric field strength. 5 is the RS from the receiving units 3 and 4
It is an A / D converter that converts SI signals and baseband signals into digital signals. Reference numerals 6 and 7 denote exponential converters that convert the input digitized RSSI value into an exponential number and make it an antilog. 8, 9 represent the R obtained from the exponential converters 6, 7
This is a multiplier that weights the baseband signal obtained from the A / D converter 5 according to the magnitude of the SSI signal. 1
An adder 0 adds and outputs the signals from the multipliers 8 and 9.

An outline of the operation of the diversity receiver is described below. When the received electric field strengths of the antennas 1 and 2 are S1 and S2, respectively, the R
The output of the SSI value is 20 log (S1), 20
log (S2). Therefore, S1 and S2 are output from the exponential converters 6 and 7, respectively. Then, multipliers 8 and 9 weight the baseband signals b1 and b2 by the square of the received electric field strength, and output S12b1 and S22b2, respectively. Finally, those signals are added to adder 1
A signal S12b1 + S22b2 is output as a demodulated output. In this way, it is possible to obtain a composite output in which the baseband signal is weighted by the square.

[0005]

However, since the above-described conventional configuration includes exponential conversion and multiplication processing, a complicated logic circuit or a high-speed digital signal processor (DSP) is required, and the circuit configuration is complicated. As a result, there is a problem that the manufacturing cost is increased.

Accordingly, an object of the present invention is to provide a diversity receiver which can be realized with a simple configuration and simple arithmetic processing.

[0007]

According to a first aspect of the present invention, there is provided an A / D converter for converting a received electric field strength and a baseband signal in each of a plurality of receiving units into a digital signal, and the A / D converter. Weighting means for weighting the baseband signal digitized by the device in accordance with the received electric field strength, and addition means for adding the weighted baseband signal, wherein the combined signal output by the addition means is A diversity receiver that outputs a baseband signal, wherein the weighting unit includes a storage unit that writes a weight corresponding to the reception electric field strength,
Weighting is performed by bit-shifting the digitized baseband signal.

According to a second aspect of the present invention, the weighting means performs weighting by performing a plurality of bit shifts with different shift amounts on the digitized baseband signal and adding the bit-shifted output. I did it.

According to a third aspect of the present invention, the receiving section outputs an RSSI signal proportional to the logarithm of the received electric field strength, and the weighting means detects the maximum value among the RSSIs of the receiving sections, and Maximum value and RSSI of each of the receiving units
The difference from the value is input to the weight table.

According to a fourth aspect of the present invention, the weighting means is performed by a microprocessor.

According to a fifth aspect of the present invention, the receiving section has an attenuator, and a means for adding the attenuation of the attenuator to the RSSI value.

[0012]

According to the first aspect of the present invention, since the weighting operation is performed by a bit shift, the configuration can be simplified.

According to the second aspect of the invention, there is an effect that a fine weighting other than the power of 2 can be performed.

According to the third and fifth aspects, it is particularly advantageous when the number of antennas is three or more.

According to the fourth aspect of the present invention, since multiplication and exponential conversion are not required, arithmetic processing can be performed by an inexpensive general-purpose microcomputer.

An embodiment of the present invention will be described below with reference to FIGS. (Embodiment 1) FIG. 1 is a configuration diagram of a diversity receiver according to Embodiment 1 of the present invention, and FIG. 2 is an example diagram of the same weight table. In FIG. 1, signals received by antennas 1 and 2 are output as a baseband signal and a received field strength (RSSI) signal by receiving units 3 and 4. Reference numeral 5 denotes an A / D converter for converting the RSSI signals from the receiving units 3 and 4 and the baseband signal into digital signals. 2
Reference numerals 1 and 22 denote subtracters that output the difference between the two RSSI signals that have been A / D converted. 23 and 24 are subtractors 21 and 22
Is a weight table that receives a signal from the controller and selects a weight according to the signal. Bit shifters 25 and 26 receive the signals from the weight tables 23 and 24 and shift the right bit accordingly. Numeral 10 denotes means for adding and outputting signals from the bit shifters 25 and 26.

Next, the detailed operation after the A / D converter 5 in FIG. 1 will be described. The RSSI values of the antennas 1 and 2 are S1 and S2, respectively, and the baseband signals are b1 and b2.
far. Since the RSSI values output from the receiving units 3 and 4 are generally values proportional to the dB values, the subtractor 21
g (S2) -20log (S1) = 20log (S2 /
The value S1) is output. Similarly, the subtractor 22 calculates
A value log (S1 / S2) is output. That is, the subtracters 21 and 22 output the decibel value of the ratio of S1 and S2. When the baseband signal is subjected to maximum ratio combining, weighting is performed according to this ratio.
That is, weighting may be performed based on the signals from the first and second signals.

Here, assuming that a weight table as shown in FIG. 2 is provided and 20 log (S1 / S2) = 8 [dB], the bit shifter 25 outputs b1 as it is, and the bit shifter 26 outputs the data of b2. Is shifted right by 2 bits and output. In this case, the output finally obtained from the adder 10 is b1 + (1/4) b2. In this way, simply using only the configuration of addition and subtraction and bit shift,
Maximum ratio combining diversity can be performed. In addition,
If the reception input has an attenuator (variable attenuator), the attenuation is added to the RSSI value.

(Embodiment 2) FIG. 3 is a configuration diagram of a diversity receiver according to Embodiment 2 of the present invention, and FIG. 4 is an example diagram of the same weight table. The configuration shown in FIG. 3 is obtained by adding bit shifters 31 to 34 and adders 35 and 36 to FIG. The bit shifters 31 and 32 receive the signal from the weight table 23 and shift the right bit accordingly. Similarly, the bit shifters 33 and 34 also receive the signal from the weight table 24 and shift the right bit accordingly. The adder 35 adds the outputs from the bit shifters 31 and 32. The adder 36 adds the outputs from the bit shifters 33 and 34. Then, the outputs from the adders 35 and 36 are added by the adder 10 to obtain a demodulated output. Note that the adders 35, 36, and 10 may be integrated.

By providing a plurality of bit shifters for one baseband signal as shown in FIG. 3, weights can be made finer than in the case of one baseband signal. For example, when there is one bit shifter, 1/2, 1/4, 1/8. . .
Weight is limited to a power of two, but if the number of bit shifters is two, it is possible to weight the baseband signal with the weight of the sum of powers of two, such as 3/4, 3/8, etc. .

Here, assuming that a weight table as shown in FIG. 4 is provided and 20 log (S1 / S2) = 8 [dB], the bit shifter 31 outputs b1 as it is, and the bit shifter 32 outputs 0. I do. The bit shifter 33 shifts the data of b2 right by 3 bits and outputs it, and the bit shifter 34 shifts the data of b2 right by 4 bits and outputs it. In this case, the output finally obtained from the adder 10 is b1 + (3/16) b2. In this manner, the characteristics can be further improved by simply performing weighting more finely than in the case of FIG. 1 using only the addition and subtraction and the bit shift.

(Embodiment 3) FIG. 5 is a configuration diagram of a diversity receiver according to Embodiment 3 of the present invention, and shows an embodiment of a diversity receiver when the number of reception input systems is three or more. Is shown. 3 antennas
More than books belong to this. In FIG. 5, the signals received by the antennas 41, 42, and 43 are output as baseband signals and RSSI by receiving units 44, 45, and 46, respectively. 47 is the RSS from the receiving units 44, 45 and 46
I, and A for converting the baseband signal to a digital signal
The / D converter 48 is maximum value detecting means for obtaining the maximum value of RSSI. 49, 50, 51 are RSS of each branch
This is a subtractor that outputs the difference between I and the maximum value of the RSSI obtained by the maximum value detecting means 48. 52, 53, and 54 are weight tables that receive signals from the subtractors 49, 50, and 51, respectively, and select weights according to the signals. 55, 56,
Reference numeral 57 denotes a bit shifter that receives signals from the weight tables 52, 53, and 54, and performs a right bit shift accordingly. Reference numeral 58 denotes an adder for adding and outputting signals from the bit shifters 55, 56, and 57.

Assuming now that there are three reception input systems and the RSSI of the second branch is the maximum, the subtractors 49 and 5
The outputs of 0 and 51 are 20 log (S2 / S1), respectively.
20log (S2 / S2), 20log (S2 / S3)
Becomes Hereinafter, as in the first embodiment, weights are selected from the weight table, the baseband signals are weighted by the bit shifter, and the weights are combined by the adder 58 to obtain a demodulated output.

(Embodiment 4) FIG. 6 is a configuration diagram of a diversity receiver according to Embodiment 4 of the present invention. In this configuration, the A / D converter 5 and the subsequent embodiments in the first embodiment are replaced with a microprocessor 61.

The operation of the microprocessor 61 is similar to the operation of the subtracters 21 and 22 of the first embodiment, the weight tables 23 and 24,
The operations performed by the bit shifters 25 and 26, the adder 10, and the corresponding elements in the second and third embodiments are performed by an operation defined by software. Since there is no multiplication in the above operation, this operation can be realized by an inexpensive general-purpose microcomputer.

[0026]

According to the present invention, in the means for weighting the baseband signal in the post-detection combining diversity system, the weighting portion can be realized only by addition and subtraction and bit shift without using exponential conversion or multiplication. Can be simplified and cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a diversity receiver according to Embodiment 1 of the present invention.

FIG. 2 is an example diagram of a weight table according to the first embodiment of the present invention;

FIG. 3 is a configuration diagram of a diversity receiver according to a second embodiment of the present invention.

FIG. 4 is an example diagram of a weight table according to the second embodiment of the present invention;

FIG. 5 is a configuration diagram of a diversity receiver according to a third embodiment of the present invention.

FIG. 6 is a configuration diagram of a diversity receiver according to a fourth embodiment of the present invention.

FIG. 7 is a configuration diagram of a conventional maximum ratio combining diversity receiver after detection.

[Explanation of symbols]

1,2,41,42,43 Antenna 3,4,44,45,46 Receiving part 5,47 A / D converter 10,58 Adder 21,22,49,50,51 Subtractor 23,24,52 , 53, 54 Weight tables 25, 26, 31, 32, 33, 34, 55, 56, 5
7-bit shifter 61 Microprocessor

Claims (5)

[Claims] An A for converting a received field strength and a baseband signal into a digital signal in each of a plurality of receiving units.
A / D converter, weighting means for weighting the baseband signal digitized by the A / D converter in accordance with the received electric field strength, and addition means for adding the weighted baseband signal. A diversity receiver that outputs a synthesized signal output from the adding unit as a baseband signal, wherein the weighting unit includes a storage unit in which a weight corresponding to the received electric field strength is written, and A diversity receiver for performing weighting by bit shifting a baseband signal. 2. The weighting means according to claim 1, wherein said weighting means performs a plurality of bit shifts having different shift amounts on said digitized baseband signal, and performs weighting by adding said bit shifted output. Item 7. The diversity receiver according to item 1. 3. The receiving section outputs an RSSI signal proportional to the logarithm of the received electric field strength, and the weighting means detects a maximum value among RSSIs of the receiving sections, and outputs a maximum value of the RSSI and each of the RSSIs. 2. The diversity receiver according to claim 1, wherein a difference from the RSSI value of the receiving unit is input to a weight table. 4. The diversity receiver according to claim 1, wherein said weighting means is performed by a microprocessor. 5. The diversity receiver according to claim 3, wherein said receiving section has an attenuator and means for adding an amount of attenuation of the attenuator to an RSSI value.