JPS61161035A - Synthesized diversity receiver - Google Patents

Abstract

PURPOSE:To obtain a diversity effect by giving a band width eliminating a spurious wave giving disturbance to a passing signal of the 1st BPF of a diversity branch to a BPF of a feedback circuit through which a synthesized diversity signal passes. CONSTITUTION:Signals having a carrier frequency fC, a modulated signal m(t) and random phases theta1, theta2 inputted respectively from antennas 1, 2 are mixed with a carrier frequency f0 from a feedback circuit by the 1st mixers 3, 4, the frequency is converted into a frequency fC-f0, the result passes through BPFs 5, 6 respectively, is subjected to amplitude limit by limiters 7, 8 and mixed with the carrier frequency fC by the 2nd mixers 9, 10. Outputs of the mixers 9, 10 are converted into the frequency f0 and synthesized by a synthesizer 11. The signal having the frequency f0 whose phase difference is eliminated because of the synthesis at the synthesized 11 is outputted through a BPF15 and a limiter 13 and fed back to the mixers 3, 4. The delay times are selected as tau1>>tau2, where tau1 is the delay time of the BPFs 5, 6 and tau2 is the delay time of the BPF15, and the band width of the BPF15 is selected as a band width B0 passing through the f0 but rejecting center frequencies fIF and fC+fIF of the BPFs 5, 6.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention combines signals received by a plurality of antenna branches in phase in order to improve the reception quality of a communication device in a wireless transmission system where fading occurs. The present invention relates to a combining diversity receiving device.

[Prior Art] FIG. 2 is a block diagram of a conventional synthetic diversity receiver, for example, the Halpern (I E E ET
rans, Com5un, ■o1. COM-22,
No. 819740, 1099-1106). In FIG. 2, the first receiving antenna 1
The first diversity branch receives the received signal from the receiving antenna 1 and the signal from the feedback circuit described below, calculates the difference in frequency between the respective signals, and outputs a signal having the frequency of the difference. a first mixer 3 that receives the signal from the first mixer 3 and passes only a predetermined band component; and a bandpass filter 5 that receives the signal from the bandpass filter 5 and amplifies and limits the amplitude. and a second mixer 9 that receives the signal from the limiter 7 and the signal from the receiving antenna 1, mixes the frequencies, and outputs a signal having a frequency that is the difference between the frequencies of the respective signals. .

Similarly to the first diversity branch, the second diversity branch that receives the signal from the second receiving antenna 2 receives and frequency-mixes the signal from the receiving antenna 2 and the output signal from the feedback circuit described above. a first mixer 4; a first bandpass filter 6 that receives a signal from the first mixer 4 and passes only a signal in a predetermined band; and a first bandpass filter 6 that receives a signal from the first bandpass filter 6; a limiter 8 that performs amplification and amplitude limitation, and a second receiving antenna that receives the signal from the limiter 8 and the signal from the second receiving antenna 2, mixes the frequencies, and outputs a signal having a frequency that is the difference between the respective signal frequencies. It is composed of a mixer 10.

The feedback circuit includes a combiner 11 that combines the signals from the second mixers 9 and 10, and a second bandpass filter 12 that receives the signal from the combiner 11 and passes only predetermined band components. The limiter 13 receives the signal from the second bandpass filter 12 and amplifies and limits the amplitude.

Next, the operation will be explained. The received signals rc 1(j) +/9°re, 2-1), - of each of the receiving antennas 1 and 2 are sent to the first mixer 3.4 and the second mixer 9.10, respectively. Supplied.

Here, f is the carrier frequency of the received signal, m(t) is the modulated signal, and θ7. θ2 is a random phase due to fading. In addition, the limiter 13 of the feedback circuit
The output signal from t. 2d rx (tΩ-, and “
. is the output frequency of the feedback circuit. A first mixer 3.4 performs frequency mixing of the received signal from the receiving antenna 1.2 and the output signal from the limiter 13, and a bandpass filter 5.6, a limiter 7.
8 to a second mixer 9.10, respectively.

At this time, the output signals of limiter 7.8 are (f
c fo shitami, (f c fo )
Z! It is engineering. In the second mixer 9.10, the signal from the limiter 7.8 and the signal from the receiving antenna 1.2 are frequency mixed and applied to the combiner 11.

The output signals of the second mixer 9 and 10 are both r o and is (tΩ-). .4 and is fed back to the next stage circuit (not shown).

[Problems to be Solved by the Invention] The conventional synthetic diversity receiver is configured as described above, and the bandpass filter 12 of the feedback circuit has a bandwidth that eliminates spurious (unwanted wave) components. (Japanese Unexamined Patent Publication No. 125536/1983).

FIG. 3 shows the output signal components from the second mixer 9.10. In FIG. 3, r+r indicates the center frequency of the first band-pass filter, fo. is the frequency of the output signal (desired signal) from the feedback circuit, and W indicates the transmission bandwidth of the received input signal. Now, the delay time of the first bandpass filter 5.6 is τ7, and the delay time and bandwidth of the second bandpass filter 12 are each 2.8.
Then, the above diversity method is τ,〉〉τ
2. and W<<8...If the condition (1) is satisfied, it is possible to operate (that is, a diversity effect can be obtained). Therefore, if the value of τ2 is made small, that is, the value of B is made large, the above equation (1) is satisfied. However, in this case, as shown in FIG. 3, a spurious component exists in the bandwidth B of the second bandpass filter 12, causing the following problem.

When the second bandpass filter 12 passes the rIr component, it passes through the first mixer 3.4 to the bandpass filter 5.4.
6 center frequency. Also, the component of fC+fIr is mixed with the input received signal in the first mixer 3.4 to produce rIr.
This becomes the r component. In either case, spurious components will exist, and a sufficient diversity effect will not be obtained.

Therefore, the object of this invention is to eliminate the above-mentioned drawbacks and to
It is an object of the present invention to provide a synthetic diversity receiving device which can operate even when a feedback circuit uses a wideband bandpass filter that satisfies the conditions of 2 and W<<8 and allows spurious components to pass.

[Means for solving the problem] The bandwidth of the second bandpass filter included in the feedback circuit is set to the following bandwidth.

That is, in each diversity branch, among the four sufuria components generated by frequency mixing in the second mixer, when frequency-mixed in the first mixer and applied to the first band-pass filter, the first band-pass component is The bandwidth is wide enough to remove only spurious components that interfere with the desired signal passing through the filter.

[Operation] With the above configuration, the conditions τ, >>τ2 and 3>>W are satisfied, and there is no spurious component that becomes interference noise, so the composite diversity receiver can operate normally. .

[Embodiments of the invention] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a synthetic diversity receiving device according to an embodiment of the present invention, and parts that are the same as or equivalent to those of the conventional synthetic diversity receiving device shown in FIG. 2 are given the same numbers. ing. As a feature of the present invention, a bandpass filter 15 having a bandwidth different from that of the conventional one.
is provided in the feedback circuit. The bandwidth of this third bandpass filter 15 is the bandwidth B0 shown in FIG.
It is. That is, among the spurious components generated during frequency mixing in the second mixer 9.10, the first
to the mixer 3.4 of the receiving antenna 1.
．． After being frequency-mixed with the signal from 2, when applied to the first band-pass filter 5.6, only spurious components that interfere with the desired signal passing through the first band-pass filter 5.6 are removed. is the bandwidth So.

The operating principle of the circuit according to an embodiment of the present invention shown in FIG. 1 is the same as that of the conventional combined diversity receiver shown in FIG. 2, but as shown in FIG. The output components from .10 include the desired signal 'o', "-""≧Y", and spurious components. but,
The bandpass filter 15 according to the invention is 2f+ in FIG.
Components such as r, fo, and "." are passed, but f l r e
f C+ f Ir component is removed. therefore,
The output component from the first mixer 3.4 does not include the flr and fc+f+r components and is filtered by the bandpass filter 5.6.
It will never be a component within the band.

In the above embodiment, the limiter 7.8 is connected to the first bandpass filter 5.6, but it may be connected before the bandpass filters 5, 6, and the limiter 7.8 may be connected before the bandpass filters 5, 6. may be replaced with a band amplifier.

Further, the limiter 13 may be replaced with an amplifier.

Broadly speaking, even when the synthetic diversity receiving apparatus of the present invention is applied to a receiver that utilizes an intermediate frequency from a tuner, the same effects as in the above embodiments can be obtained.

[Effects of the Invention] As described above, according to the present invention, the bandpass filter included in the feedback circuit does not contain spurious components that do not interfere with the signal passing through the bandpass filter connected to the first mixer. Since the configuration is configured to pass only the desired signal components, the conditions τ,〉〉2 and W〈B are satisfied, and there are no problems caused by spurious components, so this composite diversity receiver can be operated. Become.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a composite diversity receiving apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram showing the configuration of a conventional synthetic diversity receiver. FIG. 3 is a diagram showing spurious components included in the output of the second mixer. In the figure, 3.4 is the first mixer, 5 and 6 are the first bandpass filters, 7.8 is the limiter, and 9.10 is the second
11 is a synthesizer, 12 is a conventional band-pass filter, 13 is a limiter, and 15 is a band-pass filter of the present invention. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] Signals from a plurality of antennas are combined by a combiner via a diversity branch provided in each of the plurality of antennas, and the output of the combiner has a first band-pass filter. A composite diversity receiver output via a feedback circuit, wherein each of the diversity branches includes a first mixer that receives a signal from the antenna and an output signal from the feedback circuit and performs frequency mixing. , a second bandpass filter that receives the signal from the first mixer and passes only a predetermined band component; and a second bandpass filter that receives the signal from the antenna and the signal from the second bandpass filter. a second mixer that performs frequency mixing and provides the result to the synthesizer, and the first bandpass filter filters out the second bandpass among unnecessary waves generated by frequency mixing in the second mixer. A synthetic diversity receiving device characterized by having a pass band that removes unnecessary waves that interfere with signals passed by a filter.