JPS61177828A - Combined diversity receiver - Google Patents

Abstract

PURPOSE:To synthesize received signals in the same phase by simple constitution by providing a phase adjusting device to a feedfoward loop that applies frequency conversion to input signals from plural antennas. CONSTITUTION:Input signals from antennas 1, 2 are mixed with a signal 14 from a feedback circuit 30 in the first mixers 3, 4 of feedfoward loops 40, 41, applied with frequency conversion, amplified b y amplifiers 7, 8 and inputted to the second mixers 9, 10 through transformers 16, 17, BPF 5, 6 and transformers 17, 18. Group delay time of the amplifiers 7, 8 are adjusted by transformer 16-19 and inputted to mixers 9, 10, mixed with input signals from antennas 1, 2, and the output is synthesized by a synthesizer 11. In such a case, transformers 16-19 are adjusted to make output of mixers 9, 10 same in phase and synthesized 11, and passed through a BPF 12 and a limiter 13 of the circuit 30, and the output signal 14 is sent to a detector 15.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a combining diversity receiving device that combines received signals of two or more antennas in the same phase in order to improve communication quality in wireless communication where fading occurs. It is related to.

[Conventional technology]

FIG. 2 shows a conventional synthetic diversity receiving apparatus disclosed in, for example, Japanese Patent Application Laid-Open No. 57-125536. In the figure, 1 and 2 are receiving antennas; 3.4 is a first mixer that takes the frequency of the difference between the received signal from the receiving antenna 1.2 and the output signal of a feedback circuit, which will be described later; 5;
6 is an amplifier that amplifies the output signal of the first mixer 3°4;
7 and 8 are band-pass filters connected to the output of the amplifier 5.6, and 9.10 is a filter that takes the frequency of the difference between the output signal of the band-pass filter 7.8 and the output signal from the receiving antennas 1 and 2. 2 mixer, 11 is a synthesizer that combines the outputs of the second mixer 9 and 10, 30 is a feedback circuit that feeds back the output signal to the first mixer 3, 4, and this feedback circuit 30 includes a band pass filter 12 and It has a limiter 13. 14 is an output signal, and 15 is a detector.

Next, the operation will be explained. Receiving antenna I.

2 received signals as fl m(tl+& , [1/m
(t) Set to 1. However, fl is the carrier frequency of the received signal, m (tl is the modulation signal, and θ1 and θ2 are random phases due to fading. This received signal passes through the feedback circuit routers 7 and 8 in the first mixers 3 and 4,
Its output signal is (fl-fo)ZLL, (fl f
o) Becomes ZLL. This output signal and the received signal are mixed in a second mixer 9.10. The output signals of the second mixer 9.10 are then combined by a combiner 11,
It is fed back to the first mixer 3.4 via the bandpass filter 12 and limiter 13. Also, the output signal 14 is transmitted to the detector 1
The wave is detected at 5.

[Problem that the invention seeks to solve]

Since the conventional synthetic diversity receiver is configured as described above, it has two feedforward loops 40,
There is a problem in that a difference occurs in the fixed phase shift in the detector 41, and this causes distortion and noise in the output signal of the detector 15.

The present invention has been made in order to improve such conventional problems, and an object of the present invention is to obtain a composite diversity receiving device in which a phase difference between feedforward loops 1 does not occur.

Here, the causes of problems in the conventional device described above will be explained below. The group delay time of bandpass filter 7.8 is τ
1. Let τ1'' be the delay time of the feedback circuit 30, and τ2 be the delay time of the feedback circuit 30. Further, the phases of the received signals of the receiving antennas 1.2 are respectively 2πflt+θ1 2πf1t+θ2, and the phase of the output signal 14 of the feedback circuit 30 is 2πfOt. In the first mixer 3.4, the received signal and the output signal 14 of the feedback circuit 30 are mixed, and the phases of the output signals are respectively 2π(fl-fo)t+01 2π(fl-fO)t+θ2. The output signal of 3.4 passes through a bandpass filter 7.8, and the phase of its output is 27E (fl-f□) (t rl) +
θl=2πflF(t-τ1)+01 2yc (fl-fo) (t-rl')
+θ2=2πflF(t-τ1”)+θ2. flF is the center frequency of the bandpass filter 7.8. The signal that has passed through the bandpass filter 7.8 is mixed with the received signal in the second mixer 9, 1o. and the phase of the output signal is 2rcr□ t+'1rcf
lFr1 −(1)2πf□ t+2yrfI
Ft1° ・(2).

Then, the signal having the phase of equations (11, (2)) is sent to the combiner 11
is synthesized with At this time, if τ1=τ1', the received signals are combined in the same phase, but in reality, τ1 and τ1' are not completely the same, so the second mixer 9. A phase difference occurs in the phase of the output signal of lO. Therefore, this causes distortion and noise in the detector output.

Here, the analysis of Ha I pern < IEEE Tra
ns, Common, +VO1, C0M-22, N1
81974 pp. 1099-1106), the frequency of the feedforward loop is expressed as τ1+τ2. k is an integer such that flF is pulled within the bandwidth of the bandpass filter 7.8.

Therefore, if there is a difference between τ1 and τ1°, the following will occur. That is, the receiving antenna 1 is mainly used as flF-(fl τ2 +k) / (τ1 +τ2
), the frequency fQ of the output signal 14 is: At this time, the frequency of the feedforward loop 141 of the receiving antenna 2 is also operating at fIF.

When the level of receiving antenna 1 decreases and the system of receiving antenna 2 becomes dominant, it operates as flF" - (flτ2 + k) / (2 at τ1° +), and the frequency of output signal 14 at that time is rO
'=r1-flF'. Therefore, the frequency of the output signal 14 changes from fQ to f
It will fly to Q'.

The phase shift of the feedforward loop can also be caused by components other than the bandpass filter 7.8.

Therefore, even if τ1=τ1', a phase shift difference between the feedforward loops 1 occurs.

[Means for solving problems]

Therefore, the combined diversity receiving apparatus according to the present invention is provided with phase adjustment means in each feedforward loop.

[Effect]

In this invention, the phase adjustment means prevents a fixed phase shift difference from occurring between each feedforward loop, making it possible to combine received signals in the same phase.

C Embodiment] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1st
In the figure, 16.17 is a transformer (phase adjustment means) that can adjust the group delay time, and 18.19 is a transformer (phase adjustment means) provided before and after the bandpass filter 8.
It is. Further, the other configurations are the same as those in FIG. 2.

Next, the operating principle and effects of this embodiment will be explained. To simplify the explanation, it is assumed that each mixer is ideal and there is no phase shift; however, this assumption does not affect the effectiveness of this embodiment in any way.

The group delay times of the amplifiers 5 and 6 are tl and t1', the group delay time of the bandpass filter 7 including the transformer 16.17 is t2, and the group delay time of the bandpass filter 8 including the transformer 18.19 is t2. '. The received signal and the output signal 14 of the feedback circuit 30 are transferred to a first mixer 3.
4, and the phase of the output signal is mixed by the second mixer 9.
．． 10, respectively 2π(fl-fo)(t-tl-t2)+θ12π(f
t-fo)(t-tt'-t2")+02. Therefore, the phase of the output signal of the second mixer 9.10 is:
2yrf□ t+2πflF (tl +t2)2πr, respectively
□t+2πfIF(tl'+t2''). At this time, by adjusting each transformer 16, 17, 18°19, the group delay time t2°t2' can be adjusted, and thereby 2πflF(tl+t2) = 2πflF(tl '+t2') - (3>), and the received signals can be combined in phase.

This in-phase signal passes through the feedback circuit 30 and the following relationship is established.

2πf□ t=2ycfo (t r2)+2πfI
According to F (tl +t2)-2, π follows. From equations (3) and (4), t2. By adjusting t2', the received signals can be synthesized in phase, and it is also possible to set fIF to the center frequency of the bandpass filter 7.8. Therefore, no distortion or noise occurs in the output of the detector 15.

In the above embodiment, the transformer is provided before and after the band-pass filter, but the transformer may be provided either before or after the band-pass filter. Further, it may be provided at the input or output of the first mixer, the amplifier, or the input of the second mixer. Furthermore, even if the transformer is replaced with a tuned circuit, the same effects as in the above embodiment can be obtained.

Further, in the above embodiment, each feedforward loop is provided with a phase adjustment means, but this may be provided in only one feedforward loop, and the same effect as in the above embodiment can be obtained.

Furthermore, the present invention can be applied to a receiver using an intermediate frequency, and the same effects as in the above embodiment can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, since the phase adjustment means is provided in the feedforward loop, it is possible to combine received signals in the same phase with a simple circuit.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a synthetic diversity receiver according to an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional synthetic diversity receiver. 1.2...Reception antenna, 3.4...First mixer, 7.8...Band pass filter, 9.10...Second
Mixer, 11...Synthesizer, 12...Band pass filter, 13...Limiter, 16.17.18.19.
...Transformer (phase shift adjustment means), 30...Feedback circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) A first mixer that mixes each of the received signals from at least two or more antennas and a signal from a feedback circuit described below; a bandpass filter connected to the output of each of the first mixers; a second mixer that mixes the output signal of the bandpass filter and each of the received signals; a synthesizer that combines the outputs of the second mixers; and a feedback that feeds back the output signal of the synthesizer to each of the first mixers. 1. A synthetic diversity receiver comprising: a circuit; and a phase adjustment means for adjusting a phase shift between each system from the first mixer to the second mixer.