JPH02248123A - Minimum phase deviation synthesis type sd receiver - Google Patents

Abstract

PURPOSE:To improve a code error rate or the like and to enhance the reception characteristic by synthesizing a main reception signal and a sub reception signal subject to phase adjustment respectively. CONSTITUTION:A relative phase between a main reception signal and a sub reception signal from a main antenna 1 and a sub antenna 2 is controlled respectively by a phase shift means 21. Then a phase detection means 22 detects a phase difference between reception signals at plural points of a center frequency and its vicinity frequencies, for example, in a spectrum of the main reception signal and the sub reception signal and a control means 23 controls the phase deviation of the phase shift means 21 so that the deviation of the phase difference of the frequency pints is minimized. Thus, the main reception signal and the sub reception signal subject to phase adjustment are synthesized by a synthesis means 24 to obtain a synthesized wave in which an interference wave is cancelled.

Description

[Detailed Description of the Invention] [Summary] An SD receiver used for digital multiplex wireless communication, more specifically a minimum phase deviation combining type SD receiver, improves the reception characteristics by improving the bit error rate etc. of the SD receiver. A phase shift means for controlling the relative phase of the main reception signal and the sub reception signal received by the main antenna and the sub antenna, respectively, and the main reception signal and the sub reception signal after phase control by the phase shift means, If the deviation of the phase difference between each frequency point detected by the phase detection means and two-phase detection means for detecting the phase difference between the main reception signal and the sub reception signal at a plurality of neighboring frequency points in the spectrum of the reception signal is small. and control means for controlling the amount of phase shift of the phase shift means so that the amount of phase shift of the phase shift means is controlled.

[Industrial application field]

The present invention relates to a space diversity (SD) receiver used in digital multiplex radio communications, and more particularly to a minimum phase deviation combining type SD receiver.

In a digital multiplexing radio device using a multilevel QAM modulation method, multipath fading and the like caused by the combination of interference waves arriving via a propagation path different from that of the main wave causes deterioration of the bit error rate. The minimum phase deviation combining type SD receiver according to the present invention is effective in reducing the effects of multipath fading and the like.

[Conventional technology]

Conventionally, as an SD receiver, an in-phase combining type SD receiver, a minimum amplitude deviation combining type SD receiver, etc. are known.

As shown in Figure 5, the in-phase composite SD receiver uses a phase shifter to control the phases of the two received waves received by the main antenna and the auxiliary antenna (SD address) so that their phases become the same. It is synthesized by

In addition, the minimum amplitude deviation composite type SD receiver detects the amplitude value of one composite output for the center frequency of the spectrum and frequencies in its vicinity, and performs phase control using a phase shifter to minimize the amplitude deviation of these detected amplitude values. As shown in FIG. 6, as a result, the phase is controlled and synthesized so as to cancel out the interference waves.

[Problem to be solved by the invention]

In the in-phase synthesis method, thermal noise can be alleviated, but as shown in FIG. 5, interference waves remain, which affects the reduction in the bit error rate due to waveform distortion.

On the other hand, in the minimum amplitude deviation composite SD reception method, it is necessary to obtain a detection curve representing the voltage corresponding to the level of the composite output using a three-wave detector.
and 2 due to the difference in detection curves at the three frequencies.
An error occurs in the detected output voltage with respect to the composite output detection level (amplitude).

Prevents precise synthesis control.

Also, in this minimum amplitude deviation composite SD reception system.

As shown in Figure 6, the influence of interference waves can be reduced, but 7
There is a risk that the power of the composite wave will decrease, and if this decrease in composite power occurs, thermal noise will become noticeable and there is a possibility that the bit error rate will deteriorate.

Therefore, an object of the present invention is to improve the reception characteristics by improving the code error rate and the like of an SD receiver.

[Means to solve the problem]

FIG. 1 is a diagram explaining the principle of the present invention.

The minimum phase deviation composite SD receiver according to the present invention is as follows.

Phase shift means 21 that controls the relative phase of the main reception signal and the sub reception signal received by the main antenna 1 and the sub antenna 2, respectively.
and phase detection means for detecting the phase difference between the main reception signal and the sub reception signal at a plurality of neighboring frequency points within the spectrum of the reception signals, for the main reception signal and the sub reception signal after phase control by the phase shifting means 21. 22 and 3. A control means 23 for controlling the amount of phase shift of the phase shift means 21 so that the deviation of the phase difference between each frequency point detected by the phase detection means 22 is small.
It is equipped with the following.

[Effect]

The phase detection means 22 detects the phase difference between the received signals at multiple points in the spectrum of the main received signal and the sub received signal, for example, at the center frequency and the frequency adjacent to the center frequency, and the deviation of the phase difference at each of these frequency points is the minimum. The control means 23 controls the amount of phase shift of the phase shift means 21 so that . The main reception signal and the sub reception signal whose phases have been adjusted in this manner are synthesized by the combining means 24.
When combined, a composite wave is obtained in which the interference waves cancel each other out.

〔Example〕

The present invention will be described in detail below with reference to one drawing.

FIG. 2 shows a minimum phase deviation composite SD receiver as an embodiment of the present invention. In the figure, I is the main antenna, 2 is the sub antenna, the main reception wave received by the main antenna 1 is input to the mixer 3, the sub reception wave received by the sub antenna 2 is input to the mixer 4, and two local oscillators are input. By multiplying it by the oscillation output of No. 5, the frequency is converted from the RF band to the jF band. Here, 6 is an infinite phase shifter that varies the phase of the oscillation output of the local oscillator 5 according to the control signal from the control circuit 7 and supplies it to the mixer 4. This variable phase changes the phase of the oscillation output of the local oscillator 5 and supplies it to the mixer 4. The phase of Ss can be controlled.

The main reception signal SM converted into the 1F band is input to the synthesizer 11 and is also input to the three-component phase detector 8 via the amplifier 9. Similarly, the sub reception signal Ss converted to the IF band
is also input to the synthesizer 11 and also to the three-liquid phase detector 8 via the amplifier 10.

The wave phase detector 8 detects the center frequency fo of the spectrum of the received signal and the frequencies f on its left and right sides. Regarding the three points of ±Δf, the phase difference between the main reception signal SM and the sub reception signal Ss is θ1.
θ2. These circuits detect θ3, and include narrow band pass filters 81 to 86 whose center frequencies are fo and fo±8f, respectively, and these narrow band filters 81 to 8.
Phase detectors 87 to 8 detect the phase difference between the main received signal SM and the sub received signal Ss for the received signal components that have passed through the phase detectors 87 to 8.
9. Here, the two-phase detector 87 detects the phase difference θ1 at the frequency fo−Δf.

The phase detector 8th is the phase difference θ2 at frequency fo.

Further, the phase detector 89 detects the frequency f. Phase difference θ3 at 10Δf
Detect each. The detection outputs of the phase detectors 87 to 89 are output as analog voltage values proportional to the magnitudes of the phase differences θ1 to θ3.

These phase difference signals θ1 to θ3 are each input to the control circuit 7. This control circuit 7 receives an input phase difference signal θ,
The amount of phase shift of the infinite phase shifter 6 is controlled so that the deviation of ~θ3 becomes zero or minimum.

An example of the configuration of this control circuit 7 is shown in FIG.

As shown in the figure, a subtracter 71 calculates the difference between one phase difference signal θ1 and θ2, a subtracter 72 calculates the difference between two phase difference signals θ2 and θ3, and a subtracter 73 calculates the difference between the output signals of these subtractors 71 and 72. The output signal of the subtracter 73 is sent to the infinite phase shifter 6 as a control voltage signal.

The operation of the embodiment device will be explained below with reference to FIG.

It is now assumed that a received wave consisting of a combination of a main wave (direct wave) and an interference wave is input to the main antenna side and the sub antenna side, respectively. FIG. 4 shows these received waves in vector representation.

These received waves are converted from the RF band to the IF band by mixers 3 and 4, and are input to the three-component phase detector 8, respectively. The three-component phase detector 8 extracts three frequencies f from the IF spectrum of the main reception signal SM using narrow band filters 81 to 83. −Δf,
Extract the components of fo and fo+Δf. Similarly, from the IF spectrum of the sub-reception signal Ss, the narrowband filters 84 to 86
and three frequencies f. −Δf, fo, fo−Δf components are extracted. Phase detectors 87 to 89 detect each of these frequencies f.

The phase difference θ], θ2θ3 between the main reception signal SM and the sub reception signal Ss at -Δf, fo, fo+Δf is detected, and this detected voltage signal is output to the control circuit 7.

The control circuit 7 controls the phase amount of the infinite phase shifter 6 in a direction in which the phase deviation of these phase differences θ1 to θ3 becomes zero. As a result, as shown in FIG. 4, the phase of the sub-reception signal Ss changes, and the interference wave of the main reception signal SM and the interference wave of the sub-reception signal Ss cancel each other out in the combiner 11, resulting in two combined waves. will mainly consist of only the main wave component.

According to the above-mentioned method, since amplitude detection of the received signal is not performed during two-phase synthesis, there is no need to adjust the three-component detector, and errors caused by differences in detection curves are also eliminated.

Various modifications are possible in implementing the invention. For example, in the above embodiment, an infinite phase shifter that changes the phase of the sub-reception signal is provided in the frequency conversion circuit between the RF band and the IF band, but the invention is not limited to this, and for example,
It may be provided in the signal path of the sub-reception signal in the IF band, or may be provided in the signal path of the sub-reception wave in the RF band. It is also possible to provide it on the main reception signal side instead of on the sub reception signal side.

Further, although an infinite phase shifter is used as the phase shifting means, it is of course not limited to this, and other types of incest may also be used. The configuration of the control circuit for determining the phase deviation between the main reception signal and the sub reception signal is not limited to that of the embodiment, and various types of circuits for determining the five phase deviations can be used.

〔Effect of the invention〕

According to the present invention, compared to the minimum amplitude deviation composite SD receiver, there is no need to obtain the detection curve of the three-wave detector, so there is no reduction in the bit error rate due to amplitude errors generated in the three-wave detector. Receiving characteristics can be improved.

In addition, the amplitude level of the composite wave may decrease in the minimum amplitude deviation composite type SD, but the minimum phase deviation composite type S of the present invention
In D, since the received waves are combined in the increasing direction, there is no decrease in the ratio to thermal noise due to a decrease in level, that is, there is no deterioration in the code error rate.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention. FIG. 2 is a block diagram showing a minimum phase deviation combining type SD receiver as an embodiment of the present invention. FIG. 3 shows an example of the configuration of a control circuit in the embodiment device. FIG. 4 is a vector representation diagram of received waves for explaining the operation of the embodiment device. FIG. 5 is a diagram for explaining a conventional in-phase combining type SD receiving system, and FIG. 6 is a diagram for explaining a conventional minimum amplitude deviation combining type SD receiving system. In fig. 1 - Raw antenna 2 - Sub antenna (SD antenna) 3.4 ~ Mixer 5 = - Local oscillator 6 - Infinite phase shifter 7 - Control circuit 8 - Three-component phase detector 9, 1 (1---A G C amplifier 11 - combiners 71 to 73 - subtractors 81 to 86 - narrow band filters 87 to 89 - phase detector

Claims (1)

[Claims] Phase shifting means (21) for controlling the relative phase of the main received signal and the sub received signal received by the main antenna (1) and the sub antenna (2), respectively; phase detection means (22) for detecting the phase difference between the main reception signal and the sub reception signal at a plurality of neighboring frequency points in the spectrum of the reception signals, respectively, for the main reception signal and the sub reception signal after phase control by; and a control means (23) for controlling the amount of phase shift of the phase shift means (21) so that the deviation of the phase difference between each frequency point detected by the phase detection means (22) is small. Phase deviation composite space diversity receiver.