JPS61161036A - Synthesized diversity receiver - Google Patents

Abstract

PURPOSE:To bring a required signal to a higher level than that of spurious component at all times even when the reception level is lowered due to fading by amplifying an input signal from an antenna and supplying the result to the 1st and 2nd mixers. CONSTITUTION:A signal inputted from antennas 1, 2 whose phase is changed respectively by a carrier frequency fC is amplified by amplifiers 16, 17 and fed to the 1st mixers 3, 4 and the 2nd mixers 9, 10 respectively. The signal given to the mixers 3, 4 is mixed with a signal having a frequency f0 from a feedback circuit and outputs pass through BPFs 5, 6 and limiters 7, 8 respectively and are fed to the mixers 9, 10. The mixers 9, 10 mix two input signals, converts them into a signal having the frequency f0, both the output signals are synthesized by a synthesizer 11 and its output signal is outputted via a BPF15 and a limiter 13 and fed back to the mixers 3, 4. The band width of the BPF15 is selected as a band width rejecting a spurious wave giving disturbance to a passing signal of the BPFs 5, 6 among spurious waves generated by the mixers 9, 10 to actuate the diversity normally.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention aims to improve the reception quality of a communication device in an uncombined transmission system in which fading occurs, by in-phase transmitting signals received by a plurality of antenna branches. The present invention relates to a combining diversity receiving device that performs combining.

[Prior Art] FIG. 2 is a block diagram of a conventional synthetic diversity receiving device.
7rans, Go+uun, Vol, C0M-
22, No. 81974 0.1099-1106). In FIG. 2, the first diversity branch receiving the signal from the first receiving antenna 1 is
a first mixer 3 that receives a received signal from the receiving antenna 1 and a signal from the feedback circuit, calculates a difference in frequency between the respective signals, and outputs a signal having a frequency corresponding to the difference; A bandpass filter 5 receives the signal from the mixer 3 and passes only a predetermined band component; a limiter 7 receives the signal from the bandpass filter 5 and amplifies and limits the amplitude; A second mixer 9 receives the signal from the receiving antenna 1, performs frequency mixing, and outputs a signal having a frequency that is the difference between the frequencies of the respective signals.

Also, like 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 simulated feedback circuit. 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 for amplifying and amplitude components; and a second receiving antenna for receiving the signal from the limiter 8 and the signal from the second receiving antenna 2, frequency-mixing the signals, and outputting 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 'cl!' of each of receiving antennas 1 and 2 are ! −↓t)+1yu＊'
Ciii! - Engineering” - and 22! 1- is the first mixer 3゜4
and are supplied to second mixers 9 and 10, respectively. Here, fc is the carrier frequency of the received signal, -(1) is the modulated signal, θ4. θ2 is a random phase due to fading. Further, the output signal from the limiter 13 of the feedback circuit is fo/1 (1), where fo is the output frequency of the feedback circuit. The received signal from the receiving antenna 1.2 and the limiter 13 in the first mixer 3.4
Frequency mixing is performed with the output signals from the respective output signals, and the resulting signals are respectively applied to a second mixer 9.10 via bandpass filters 5, 6 and a limiter 7.8. At this time, the output signals of limiters 7.8 are <r cr−r, respectively. )
ZL Yu, (fc-r.) ZL Yo. 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 9.10 are both f. Z1 Yu Do Yu. The signal synthesized by the synthesizer 11 is fed back to the first mixer 3.4 via the second bandpass filter 12 and limiter 13, and is also applied 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. (See Japanese Unexamined Patent Publication No. 57-125536).

FIG. 2 is a diagram showing output signal components from the second mixers 9 and 10. In FIG. 2, flF is the center frequency of the first bandpass filter, and f is the center frequency of the first bandpass filter.

is the output signal (desired signal) frequency from the feedback circuit, and W is the transmission bandwidth of the input received signal.

Now, the delay time of the first bandpass filter 5.6 is τ1,
Assuming that the delay time and bandwidth of the second bandpass filter 12 are respectively τ21B, the above-mentioned diversity method has the following characteristics: τ1>>τ2. and W<<8...(1)
It is possible to operate (that is, a diversity effect can be obtained) if the following conditions are met. Therefore, if the value of τ2 is decreased, that is, the value of B is increased, the above equation (1)
is satisfied. However, in this case, as shown in FIG. 2, spurious components exist across the bandwidth of the second bandpass filter 12, causing problems as described below.

When the second bandpass filter 12 passes the r+r component, it passes through the first mixer 3.4 and passes through the bandpass filter 5.4.
6 center frequency. Also, the component of t(+f l y is mixed with the input received signal in the first mixer 3.4 and r
+r component. In either case, spurious components will exist, making it impossible to obtain a sufficient diversity effect.

Furthermore, the second bandpass filter 12 is "1r.

Even if r c+r l r can be removed, if the level of the spurious component within the band of the second bandpass filter 12 is higher than the level of the desired signal f0, the desired signal r. is not amplified by the limiter 13, and this composite diversity receiving device becomes inoperable.

Therefore, the object of this invention is to eliminate the above-mentioned drawbacks and to
,>>τ2 and W<<B, and is operable even when a wideband bandpass filter through which spurious components pass is used in a feedback circuit.

[Means for solving the problem] In the present invention, in each diversity branch, means for amplifying the signal from the receiving antenna is provided between the receiving antenna and the first mixer, and further included in the feedback circuit. The bandwidth of the second bandpass filter is assumed to be as follows. That is, in each diversity branch, among the spurious components generated by frequency mixing in the second mixer, when the spurious components are frequency-mixed in the first mixer and applied to the first band-pass filter, the first band-pass filter The bandwidth is wide enough to remove only spurious components that interfere with the desired signal passing through.

[Operation] With the above configuration, the conditions τ1>>τ2 and B>>W are satisfied, and there is no spurious component that becomes interference noise, and even if the reception level decreases due to fading etc. Since the received signal is amplified by the amplification means, the desired signal is always at a higher level than the spurious components, and the composite diversity receiver can operate normally.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described 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, the third bandpass filter 15 having a bandwidth different from that of the conventional one is connected to the feedback circuit synthesizer 11 and limiter 13.
established between. This third bandpass filter 15
The bandwidth of is shown in Figure 2? ! Range B. It is. That is, among the spurious components generated during frequency mixing in the second mixer 9 and 10, the first mixer 3
．． 4 and frequency mixed with the signal from the receiving antenna 1.2 in the rear cylinder 1.
respectively, the first bandpass filter 5
．． Bandwidth B for removing spurious components that interfere with the desired signal passing through 6. It is.

Roughly speaking, as a feature of this invention, each receiving antenna 1.2
and the first mixer 3.4, each receiving antenna 1
．． Amplifiers 16 , 17 are provided which amplify the input received signals from 2 to raise the level of the desired signal higher than the level of the spurious components passing through the third bandpass filter 15 .

The operating principle of the circuit shown in FIG. 1, which is an embodiment of the present invention, is the same as that of the conventional combined diversity receiver shown in FIG. However, as shown in the second factor, the output components of the second mixers 9 and 10 contain the desired signal "
. Contains Z1 and spurious components. but,
The bandpass filter 15 according to the invention is 2fI in FIG.
r, f. Although components such as and fc are passed through, f, , fc
+rlF component is removed. Therefore, the output components from the first mixers 3 and 4 include rIrj5 and fe+f,
component is not included and will not be a component within the band of the first bandpass filter 5.6.

Next, consider a case where the input received signal level drops. At this time, in the conventional receiving device, the second mixer 9.
10 outputs a spurious component 2f+r at a level higher than the level of the desired signal r0, making it impossible for the receiver to operate. However, in the receiving apparatus of the present invention, the amplifiers 16, 17 amplify the input received signals from the receiving antenna 1.2, and the first mixer 3.4
and a second mixer 9.10, respectively.

Therefore, the signals from limiters 7, 8 and amplifier 16
．． 17 are the amplified input received signals from the second
Since the frequency is mixed by the mixer 9.10, the level of the desired signal component 0 becomes higher than the level of the 2f1° component, and the desired signal component 0 becomes higher than the level of the 2f1° component.

can be amplified by the limiter 13, so the above-mentioned conventional problems are solved.

In the above embodiment, the amplifiers 16.17 input the received signal from the antenna 1.2 to the first mixer 3.4.
and the second mixer 9, 10, but so as to amplify only the input received signal component that is applied to the mixer 9, 10 of the rear tube 2 after the input received signal is distributed. It may also be provided before the second mixers 9 and 10.

Furthermore, the amplifiers 16 and 17 of the present invention may be band-limited amplifiers that do not amplify components other than the received signal.

Further, in the embodiment described above, the limiter 7.8 includes a bandpass filter 5.6 and a second mixer 9.10, respectively.
Although the first mixer 3.4 is connected between the first mixer 3.4 and the bandpass filter 5.6, it may be configured to be provided between the first mixer 3.4 and the bandpass filter 5.6.

The limiters 7.8 and 13 may also be amplifiers.

Further, even when the synthetic diversity reception equipment 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 separates the spurious components that do not interfere with the signal passing through the bandpass filter connected to the first mixer and the desired spurious components. It has a bandwidth that allows the signal components to pass through, and is configured to amplify the input received signal from the receiving antenna. Therefore, the conditions of τ1>>τ2 and W x B are satisfied, and no problem occurs due to spurious components, and this combined diversity receiving apparatus becomes operable.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a composite diversity receiver according to an embodiment of the present invention. FIG. 2 is a diagram showing spurious components included in the output of the second mixer. FIG. 3 is a block diagram showing the configuration of a conventional synthetic diversity receiver. In the figure, 3.4 is the first mixer, 5.6 is the first bandpass filter, 7.8 is the limiter, and 9.10 is the second
11 is a synthesizer, 12 is a conventional bandpass filter, 13 is a limiter, 15 is a bandpass filter of the present invention, and 16.17 is an amplifier. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (3)

[Claims] (1) 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 is sent through a feedback circuit having a first bandpass filter. a composite diversity receiving device that outputs a signal from the feedback circuit, each of the diversity branches comprising: a first mixer that receives a signal from the antenna and an output signal from the feedback circuit and performs frequency mixing; a second band-pass filter that receives the signal from the mixer and passes only a predetermined band component; and a second band-pass filter that receives the signal from the antenna and the signal from the second band-pass filter and performs frequency mixing. a second mixer that supplies the antenna to the combiner; and a second mixer provided between the antenna and the first mixer;
and an amplifying means for amplifying a signal from the antenna, and the first bandpass filter is configured to transmit a signal that the second bandpass filter passes among unnecessary waves generated by frequency mixing in the second mixer. 1. A synthetic diversity receiving device characterized by having a passband that removes unnecessary waves that cause interference. (2) The output signal of the amplifying means is provided to the first mixer and the second mixer.
The synthetic diversity receiving device described in . (3) The composite diversity receiving device according to claim 1, wherein the output signal of the amplifying means is provided only to the second mixer.