JPH1168647A - Diversity receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain the quality of a received signal by performing weighting from a reception level outputted from a plurality of reception level detection circuits and the phase error of demodulated signals outputted from a plurality of demodulation circuits. SOLUTION: Reception level detection circuits 10a and 10b detect received signal level from received signals outputted from antennas 1 and N and demodulation circuits 11a and 11b demodulate them so that phase information can be provided. Phase error calculation circuits 12a and 12b calculate the phase difference of this phase information and phase information outputted from a discrimination circuit 15. The found phase error is inputted to weight calculation circuits 13a and 13b, and the synthetic weight synthesizing the received signal level output and phase error output is found. The more the phase error is found, the more the weight is reduced. When the level weight of a received signal at a k-th branch and an m-th symbol is Akm and the weight caused by the phase error is Bkm , a signal synthesizing circuit 15 calculates synthetic weight Ckm as Ckm =aAkm +bBkm on the condition of a+b=1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a diversity receiver for preventing deterioration of transmission quality.

[0002]

2. Description of the Related Art Conventionally, diversity receivers have been used to prevent deterioration of transmission quality due to fading in which an electric field at a receiving point fluctuates with time. By the way, in mobile communication, a transmission path becomes a multipath transmission path, and fading occurs. If the reception level is attenuated or intersymbol interference occurs due to fading, the reception sensitivity is degraded. Therefore, fading countermeasures have become an important problem. As a measure for preventing reception sensitivity deterioration due to fading, diversity reception in which a plurality of antennas (branches) receive signals is used. In this diversity reception,
In general, demodulation is performed for each branch, and a demodulation output is selected or combined. Diversity reception in which a demodulated signal is weighted more heavily for a branch signal having a higher reception level and the respective demodulated signals are combined is called post-detection combined diversity reception.

FIG. 3 is a block diagram of a conventional diversity receiver using N antennas. In FIG.
50a, 50b, 50c are reception level detection circuits for detecting the reception signal levels of the antennas 1, 2, N, 51
a, 51b, and 51c are demodulation circuits for demodulating received signals received by the antennas 1, 2, and N, and 52a, 52b, and 5c.
2c denotes each of the reception level detection circuits 50a, 50b, 50
A weighting circuit that weights the output signals (demodulated signals) from the demodulation circuits 51a, 51b, and 51c in accordance with the output signal from c (signal indicating the level of the received signal). A signal synthesizing circuit 54 for synthesizing the output signal is a judgment circuit for judging a symbol (here, phase) based on the output signal from the signal synthesizing circuit 53.

The operation of the diversity receiver configured as described above will be described below. First, the reception signal levels of the antennas 1, 2, and N are obtained by the reception level detection circuits 50a, 50b, and 50. The signals received by each of the antennas 1, 2, N are demodulated by a demodulation circuit 51a,
Demodulated at 51b and 51c. Demodulated signals output from these demodulation circuits are weighting circuits 52a and 52a, respectively.
b, 52c, respectively, and each received level detection circuit 50
a, 50b, weighted by the output signals from 50. Each of the weighted signals is supplied to a signal combining circuit 53.
Synthesized by The synthesized signal is input to the determination circuit 54, and the symbol (here, phase) is determined.

[0005]

However, in the above-mentioned conventional diversity receiver, weighting is performed only with the received signal level, and the received signal level is large due to the influence of the same frequency interference or external noise, but the quality of the received signal is high. Even for a signal having a poor S / N ratio, for example, a large weighting is applied to combine the signals, so that there is a problem that the receiving sensitivity is deteriorated.

In this diversity receiver, it is required to perform weighting in consideration of not only the received signal level but also the quality of the received signal.

An object of the present invention is to provide a diversity receiver that can perform weighting in consideration of not only the level of a received signal but also the quality of the received signal.

[0008]

According to a first aspect of the present invention, there is provided a diversity receiver which demodulates a plurality of reception signals output from a plurality of reception antennas to obtain a plurality of reception signals. A plurality of demodulation circuits for outputting a demodulated signal; a plurality of reception level detection circuits for detecting respective levels of the plurality of received signals; and a plurality of detected phase errors of the demodulated signals output from each of the plurality of demodulation circuits. A plurality of weight calculating circuits for calculating weights from respective levels of the received signals, a signal combining circuit for combining a plurality of demodulated signals based on the weights, and a determination for determining a phase of a combined signal output from the signal combining circuit And a plurality of phase error calculation circuits for calculating a phase error based on the determined phase and outputting the calculated phase error to a plurality of weight calculation circuits.

As a result, it is possible to obtain a diversity receiver capable of performing weighting in consideration of not only the received signal level but also the quality of the received signal.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, there are provided a plurality of demodulation circuits for demodulating a plurality of received signals output from a plurality of receiving antennas and outputting a plurality of demodulated signals, A plurality of reception level detection circuits for detecting respective levels of the plurality of reception signals, and a weight is calculated from a phase error of a demodulation signal output from each of the plurality of demodulation circuits and each level of the detected plurality of reception signals. A plurality of weight calculation circuits, a signal synthesis circuit that synthesizes the plurality of demodulated signals based on the weights, a determination circuit that determines the phase of a synthesized signal output from the signal synthesis circuit, and a phase that is determined based on the determined phase. And a plurality of phase error calculation circuits for calculating an error and outputting the calculated error to a plurality of weight calculation circuits. It has the effect of but is calculated.

[0011] The diversity receiver according to claim 2 is
2. The diversity receiver according to claim 1, wherein the weight calculation circuit sets the weight value based on the received signal level to a first constant multiple obtained by multiplying the weight value based on the phase error of the demodulated signal by a first constant. Is added as a composite weight by multiplying the second constant multiplied value by the constant of (1), and an appropriate composite weight is obtained by adding the second constant multiplied value to the first constant multiplied value. Having.

According to a third aspect of the present invention, in the diversity receiver according to the first aspect, the weight calculation circuit multiplies the value of the weight due to the phase error of the demodulated signal by a first constant multiplied by a first constant. The value is multiplied by a second constant multiple obtained by multiplying the value of the weight of the received signal level by the second constant to obtain a composite weight.
This has the effect that an appropriate composite weight is obtained by multiplying the constant multiple by the second constant multiple.

Although the signal quality to be considered here is phase accuracy, even if the signal quality is amplitude accuracy and frequency accuracy,
The signal quality can be considered, and weighting can be performed in consideration of the signal quality.

An embodiment of the present invention will be described below with reference to FIGS. (Embodiment 1) Hereinafter, a diversity receiver according to Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a diversity receiver according to Embodiment 1 of the present invention. In FIG. 1, reference numerals 10a and 10b denote reception level detection circuits for detecting the reception signal levels of the antennas 1 and N, and 11a and 11b demodulate the reception signals from the antennas 1 and N and output demodulated signals indicating phases. A demodulation circuit 12a, 12b is a phase error calculation circuit for obtaining an absolute value of a difference between phase information, which is output information from the demodulation circuits 11a, 11b, and phase information, which is output information after determination in a determination circuit 15 described later, 13a , 13b respectively use the output signals from the reception level detection circuits 10a and 10b (signals indicating the reception signal level) and the output signals from the phase error calculation circuits 12a and 12b (signals indicating the phase error) to each branch (antenna). ) Is a weight calculation circuit for calculating a weight for weighting the signal (demodulated signal).
Demodulation circuit 1 according to the weight value output from 3a, 13b
A signal combining circuit that weights the demodulated signals from 1a and 11b and combines the weighted demodulated signals to obtain a combined signal. Reference numeral 15 denotes a symbol (here, a phase) using the combined signal output from the signal combining circuit 14. Is a determination circuit for performing the determination.

The operation of the diversity receiver configured as described above will be described below. First, the antennas (branches) 1 and N output a reception signal obtained by receiving a radio signal. The reception signals output from the antennas 1 and N are input to reception level detection circuits 10a and 10b and demodulation circuits 11a and 11b. Receive level detection circuit 10
a and 10b detect the level of the input received signal, and the demodulation circuits 11a and 11b demodulate the input received signal to obtain phase information. The phase information output from the demodulation circuits 11a and 11b is input to phase error calculation circuits 12a and 12b, and the phase error with the phase information output from the determination circuit 15 is calculated.

FIG. 2 is a phase diagram showing an example of a phase error when QPSK is used. In FIG. 2, the demodulation circuit 11
The phase values output from a and 11b are indicated by x points in P11, and the phase values output from the determination circuit 15 are indicated by ● points in 1a. If there is no noise or interference, the X point coincides with the ● point (1b, 1c, and 1d are other possible phase points after the determination of the QPSK signal. Here, the phase after demodulation is indicated by an X point P11. Because it is in the first quadrant, ● Point 1a (+ π
/ 4)). The phase of the above-mentioned x point P11 and ● point 1
The absolute value of the phase difference θ from the phase of a
a, 12b are the phase errors output from 12b.

The obtained phase error is calculated by a weight calculating circuit 13.
a and 13b. Weight calculation circuits 13a, 13b
Further, the reception signal level is input from the reception level detection circuits 10a and 10b, and a weight (combination weight) obtained by combining the reception signal level and the phase error is obtained. k (1 ≦ k ≦
The weight B _km due to the phase error θ _km of the m-th symbol in the N) -th branch is obtained by (Equation 1).

[0018]

(Equation 1)

Since the weight must be reduced as the phase error increases, f (θ) is a monotonically decreasing function, an example of which is shown in (Equation 2).

[0020]

(Equation 2)

Further, since the value of the phase error θ is at most π, it can be expressed by the equation (Equation 3).

[0022]

(Equation 3)

In equation (3), since division is unnecessary, D
It is suitable for processing such as SP (Digital Signal Processor). The value of the phase error θ is determined by the demodulation circuits 11a, 11b
Is φ _km and the phase value output from the decision circuit 15 is φ ′ _m , it is obtained by (Equation 4).

[0024]

(Equation 4)

That is, the value of the phase error θ _km of the m-th symbol in the k-th branch is the average value of the absolute value of the difference between φ _km and φ ′ _m in the past n symbols. (Equation 5) and (Equation 6) show calculation examples for obtaining the combined weight C _km when the weight based on the received signal level is A _km and the weight based on the phase error is B _km . Note that the weight A _km may be a value proportional to the received signal level value as in the conventional case.

[0026]

(Equation 5)

[0027]

(Equation 6)

In equation (5), when the weight A _km based on the reception level and the weight B _km based on the phase error are combined at the same ratio, that is, a = 0.5 (first constant) and b = 0.5
In the case of (the second constant), the composite weight C _km is the average of A _km and B _km . On the other hand, in equation (6), C _km is A _km
That the multiplication of B _miles since (first constant, 1 is a the second constant co) case A _miles than other branches B _miles is large, i.e. larger received signal level, when the phase error is small , The demodulated signal is weighted with a larger weight and synthesized. The signal synthesized by the signal synthesizing circuit 14 is input to the judging circuit 15, where the symbol is judged (here, the phase is judged).

As described above, according to the present embodiment, the composite weight C _{km is obtained} from the weight B _km based on the phase error of the demodulated signals output from the demodulation circuits 11a and 11b and the weight A _km based on the detected received signal level. Is calculated.
Weighting can be performed in consideration of not only the received signal level but also the phase error which is the quality of the received signal.

Further, the first constant multiple value bB_kmIs the second constant multiple
aA_kmAre added to obtain a first constant b and a second constant a
Of the composite weight C of various characteristics by changing the value of_kmCan get
In this case, an appropriate combined weight can be obtained. Furthermore, the first
Constant multiple B_kmIs the second constant times A _kmBy multiplying by
Weight A based on received signal level value compared to other branches _km
Is also a weight B based on the phase error value._kmIs also large
More weight on demodulated signal than just addition
Can further improve the quality of the synthesized signal.
Can be.

[0031]

As described above, according to the diversity receiver of the first aspect of the present invention, each of a plurality of received signals output from a plurality of receiving antennas is demodulated to output a plurality of demodulated signals. A plurality of demodulation circuits, a plurality of reception level detection circuits for detecting respective levels of the plurality of reception signals, and a phase error of a demodulation signal output from each of the plurality of demodulation circuits and each of the detected reception signals A plurality of weight calculation circuits that calculate the weight from the level of the signal, a signal synthesis circuit that synthesizes a plurality of demodulated signals based on the weight,
By having a determination circuit that determines the phase of the synthesized signal output from the signal synthesis circuit, and a plurality of phase error calculation circuits that calculate a phase error based on the determined phase and output the calculated phase error to a plurality of weight calculation circuits Since the demodulated signal can be weighted by the weight based on the phase error of the demodulated signal and the weight based on the detected received signal level, the weighting takes into account not only the received signal level but also the phase error that is the quality of the received signal. Can be obtained.

According to the invention described in claim 2, according to claim 1
In the invention described in (1), the weight calculation circuit sets the weight value based on the received signal level to a first constant multiple value obtained by multiplying the weight value based on the phase error of the demodulated signal by the first constant.
By adding a second constant multiplied value that is a constant multiplied by the constant to obtain a composite weight, it is possible to obtain composite weights of various characteristics by changing the values of the first constant and the second constant. An advantageous effect that weights can be obtained is obtained.

According to the invention described in claim 3, according to claim 1
In the invention described in (1), the weight calculation circuit calculates a first constant multiplied value obtained by multiplying the value of the weight due to the phase error of the demodulated signal by the first constant, and the weight value of the received signal level by the second constant. By multiplying by the multiplied second constant multiplication value to obtain a composite weight, when the received signal level is high and the phase error is small compared to the other branches, the corresponding demodulated signal is larger than in the case of simple addition. Since weighting can be performed, an advantageous effect that the quality of the synthesized signal can be further improved can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a phase diagram showing an example of a phase error when QPSK is used.

FIG. 3 is a block diagram showing a conventional diversity receiver.

[Explanation of symbols]

 10a, 10b Received level detection circuit 11a, 11b Demodulation circuit 12a, 12b Phase error calculation circuit 13a, 13b Weight calculation circuit 14 Signal synthesis circuit 15 Judgment circuit

Claims (3)

[Claims] 1. A plurality of demodulation circuits for demodulating a plurality of received signals output from a plurality of receiving antennas to output a plurality of demodulated signals, and a plurality of demodulation circuits for detecting respective levels of the plurality of received signals. A reception level detection circuit, a plurality of weight calculation circuits for calculating a weight from a phase error of a demodulated signal output from each of the plurality of demodulation circuits and a level of each of the detected plurality of reception signals, A signal combining circuit that combines the demodulated signal based on the weight, a determination circuit that determines the phase of the combined signal output from the signal combining circuit, and calculates the phase error based on the determined phase. A diversity receiver comprising: a plurality of phase error calculation circuits for outputting to a plurality of weight calculation circuits. 2. The weight calculation circuit according to claim 1, wherein the weight value based on the level of the received signal is a second constant value obtained by multiplying the weight value based on the phase error of the demodulated signal by a first constant. 2. The diversity receiver according to claim 1, wherein a second constant value multiplied by a constant by a constant is added as a composite weight. 3. The weight calculation circuit according to claim 1, wherein the first constant multiplied by a value obtained by multiplying the value of the demodulated signal by the phase error by a first constant is used as a second value by the level of the received signal. 2. The diversity receiver according to claim 1, wherein a multiplication weight is obtained by multiplying by a second constant multiplied value multiplied by a constant by a constant.