JPS6238623A - Combined diversity receiver - Google Patents

Abstract

PURPOSE:To eliminate the effect of the 2nd mixer due to an undesired wave outputted from the 1st mixer and due to load noise in a system from the 1st mixer to the 2nd mixer onto an output signal of the 2nd mixer by inputting an output signal from the 1st mixer to the 2nd mixer from an amplifier via a BPF. CONSTITUTION:BPFs 25, 26 are connected respectively to the output of the 1st mixers 3, 4 and the band is broad in a degree to eliminate an undesired wave outputted from the mixers 3, 4. Then the output signal of the BPFs 25, 26 is outputted from narrow band BPFs 5, 6 via limiters 7, 8 respectively. The signal outputted from the 2nd mixer 9 becomes a signal (d) having a spectrum component. THe power of noise 30 is sufficiently small and there is no problem on the effect of an output signal 14 of a feedback circuit given onto a signal outputted from a mixer 9.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a composite diversity reception method in which received signals from two or more antennas are combined in phase in order to improve reception quality in a wireless communication device where fading occurs. It is related to the device.

[Conventional technology]

FIG. 2 shows, for example, Halpern-(IEEE Tr
ans,Comm-un,,COM-22,No,8
1974. PP, 1099-1106). In the figure, 1,
2 is a receiving antenna, 3.4 is a first mixer that takes the frequency of the difference between the received signals from the receiving antennas 1 and 2 and the output signal of a feedback circuit to be described later, and 5.6 is a first mixer 3, 4. a bandpass filter connected to the output of 7
, 8 is a limiter, 9.10 is a second mixer that takes the frequency of the difference between the output signals of the limiters 7 and 8 and the output signal from the receiving antenna 1.2, and 11 is the output of this second mixer 9.10. 40 is a feedback circuit that feeds back the output signal to the first mixer 3.4, and the feedback circuit 40 includes the band pass filter 2 and the limiter 13.
have. 14 is an output signal.

Next, the operation will be explained.

Each received signal of the receiving antenna 1.2 is expressed by the following equation.

El a(t)=A(t) cos (27Rct +
m(t)+θ1)El bit)=B(t)cos
(2rcfct +m(tl+θ2) where fc is the carrier frequency, A(t) and B(t) are the amplitudes subjected to fading, m(t) is the modulation signal, and θ1 and θ2 are random phases due to fading.

It is assumed that the output signal 14 of the limiter 13 of the feedback circuit 40 can be expressed by the following equation.

EQ (t)=cos (2πfot +m<tl)
However, fO is the center frequency of the bandpass filter 2.

In the first mixer 3.4, each received signal and EO(t)
are mixed and the output is E 2a ft) = −A (t)cos (2π
fit+01)E2 b(tl=-B(tlcos
(2Tcf 1 tl01). However, f 1 (
-fc-fo) is the center frequency of the bandpass filters 5 and 6.

E2a(t) and E2b(t) are bandpass filters 5.6
Then, in the limiter 7.8, the faded amplitude @A(t), B(tl is set to a constant amplitude, and a signal with random phases θl, θ2 due to fading is output. Therefore, the limiter 7, 8 The output of E3 a(tl=cos (2if 1 t+θ1)
E3 b(tl=cos (2πflt+01)).

In the second mixer 9.10, each received signal E
1 a, El b and output signal E3 a of limiter 7.8
, E3 b are mixed, and the output is E4 b(t)−
−B(t) cos (2ffff Q t +m(t)
).

In this way, the random phase θ1. The in-phase signals E4 a and E4 b from which θ2 has been removed are combined in a combiner 11,
The signal passes through a bandpass filter 12, has a constant amplitude at a limiter 13, and is fed back. And the EQ assumed above
(t).

In order for this synthetic diversity to operate in this way, the bandpass filters 5 and 6 are required to have narrow band characteristics.
The bandwidth must be wide enough to accurately reflect the random phase, yet narrow enough to filter out noise and modulation components.

Next, random phase θ1. Let θ2 be a function of time, i.e. θ1−
01(t) and θ2-02(t). If the group delay time of the band pass filters 5 and 6 is tl, and the group delay time of the limiter 7.8 is t2, then the random phases θ1 and θ2 that have passed through the band pass filter 5.6 and the limiter 7.8 are θ1
θ1 (t-tl-t2), θ2=02 (t-tl
-t2). In the second mixer 9.10, in order to remove the random phase θ1°θ2, Δθ1=01(t)-θ1(t-t1t2)...(1
) Δθ2: θ2(t)-θ2 (t-tl-t2)・
...(2) needs to be sufficiently small.

Here, the group delay time t1 is determined by the bandpass filter 5.6.
Since the bandwidth is ±2 to 3 KHz, it is on the order of several hundred μSec. On the other hand, random phase θ1 due to fading. The frequency component of θ2 exists up to several hundred Hz.

From the above, Δθ1. In order for Δθ2 to become sufficiently small, tl
>t2, therefore, limiter 7.
8 is a wide band.

[Problem that the invention seeks to solve]

The conventional synthetic diversity receiver is configured as described above, and the limiters 7 and 8 are required to have a wide band. Therefore, in the second mixers 9, 10, there is a problem in that the self-noise of the limiters 7.8 is superimposed on the desired signal, degrading the carrier-to-noise power ratio. Furthermore, the output signal 1 of the limiter 13
4 is a high level, and is output from the first mixer 3.4 as a high level unnecessary wave. Therefore, although this is attenuated by the bandpass filters 5 and 6, it is amplified by the limiter 7.8, and there is a problem in that it affects the desired signal in the second mixer 9.10.

This will be explained below by showing a specific example.

For simplicity, we will consider one branch here. Figure 3 (a
) shows the spectral components of the FM signal at the receiving antenna 1. However, the modulation frequency fm of the modulation signal is outside the band of the bandpass filter 5, and 1. Regarding the spectrum of the modulated signal, only the fundamental wave component is considered. In the figure, 15 is the spectrum of the carrier wave, 16a is the upper wave of the modulation signal, and 16b is the lower wave of the modulation signal.

Output signal 1 of limiter 13 assuming normal operation
The spectral components of the FM signal at 4 are shown in FIG. 3 (bl), where the carrier frequency fc is converted to fO.

In the first mixer 3, FM signals having the spectra shown in FIGS. 3(a) and 3(b) are mixed, and the output from the first mixer 3 has a spectrum as shown in FIG. 3(C). In the figure, 17 is a component due to carrier wave cross-correlation, 18a
is a component due to cross-correlation of the upper side wave of the modulation signal, 18b is a component due to cross-correlation of the lower side wave of the modulation signal, 19 is the carrier wave of the feedback circuit output from the first mixer 3, and 20a is the component of the first
The upper wave 20b of the modulation signal of the feedback circuit output from the mixer 3 is the lower wave of the modulation signal of the feedback circuit output from the first mixer 3.

A signal with a spectrum as shown in Fig. 3 (C1) passes through the bandpass filter 5 and becomes as shown in Fig. 3 (d). As shown in Fig. 3(al), the output of the limiter 7 contains the spectral component (Fig. 3(d)) in the output of the bandpass filter 5 and the component amplified by the limiter 7. In addition, the self-noise 21 of the limiter 7 is included.

Therefore, in the second mixer 9, FIG. 3(a).

(When signals such as el are mixed, a component as shown in FIG. 3(f) is output. In this figure, the carrier spectrum 15 of FIG. 3(a) is converted into fO and the component is output. Figure 3 (
The component 22 on which the fo acid component outputted from the limiter 7 in e) is superimposed, the frequency-converted component of the upper side wave 16a of the modulation signal in FIG. 3(a), and the output from the limiter 7 in FIG. 3(Q) Component 23a on which f o + fm component is superimposed
, Fig. 3 (a component obtained by frequency-converting the lower side wave 16b of the modulated signal of al, and Fig. 3 (a component obtained by frequency-converting the lower side wave 16b of the modulated signal of al, Component 23b1 on which the output fo-fm component is superimposed
FIG. 3 (IJ of el) The self-noise 21 output from Mitsutaf shows the noise component 24 output from the second mixer 9.

As described above, in the second mixer 9, the received signal of FIG. 3 Ia) is distorted as shown in FIG. 3 (fl), and furthermore, the self-noise of the limiter 7 is added.

This invention was made to solve the above-mentioned problems. Even if the limiter has a wide band, the self-noise of the limiter does not affect the output signal from the second mixer, and It is an object of the present invention to obtain a composite diversity receiver in which one output signal of a circuit does not affect the output signal from a second mixer.

[Means for solving problems]

The synthesis dyno-chi receiving device according to the first invention of the present application is configured such that the output signal of the first mixer is inputted to the second mixer through an amplifier such as a limiter or a 7-stage amplifier, through a band-pass filter. .

Further, in addition to the configuration of the first invention, the composite diversity receiving device according to the second invention of the present application has a wide band in the output of the first mixer to the extent that unnecessary waves output from the first mixer can be removed. An unnecessary wave removal means such as a pass filter is inserted.

[Effect]

In the first invention of the present application, the self-noise of the amplifier is sufficiently reduced by a narrowband bandpass filter connected to the output of the amplifier, and in the second invention, in addition to this, the self-noise of the amplifier is The output signal of the feedback circuit is sufficiently reduced through a wideband bandpass filter to remove unnecessary waves, and the amplifier and narrowband bandpass filter.

〔Example〕

Hereinafter, embodiments of the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of a combined diversity receiver according to an embodiment of the second invention of the present application, and in the figure, the same reference numerals as in FIG. 2 indicate the same parts. 25 and 26 are band pass filters connected to the outputs of the first mixers 3 and 4, respectively, which have a wide band that can remove unnecessary waves output from the first mixers 3 and 4. ing. The output signals of the bandpass filters 25 and 26 are outputted from the narrowband bandpass filters 5 and 6 through limiters 7 and 8, respectively.

Next, the effects will be explained using specific examples.

Here, for simplicity, we will consider one branch.

Assume that an FM signal having a spectrum shown in FIG. 3(a) is input to the receiving antenna 1. Assuming normal operation, the spectral components of the FM signal in the output signal 14 of the limiter 13 are as shown in FIG. 3 tb).

In the first mixer 3, the signals of Fig. 3 (al, (bl) are mixed, and the spectral components of the output are
). The signal in FIG. 3(C) passes through the band-pass filter 25, which has a wide band that can remove unnecessary waves output from the first mixer 3, so fo-fm, fo, f
The o+fm components 20b, 19, and 20a are sufficiently attenuated, as shown in FIG. 4(a). A signal having a spectrum of Fig. 4(al) is amplified by the limiter 7,
'b). The signal in FIG. 4(b) passes through the bandpass filter 5 and becomes the signal in FIG. 4<e). In the figure,
27 is the self-noise of the limiter 7 output from the bandpass filter 5.

Therefore, the signal output from the second mixer 9 becomes a signal having spectral components as shown in FIG. 4 fd). In the figure, 28 is a component obtained by converting the carrier wave spectrum 15 of FIG. The lower side wave 16b of the modulated signal in a) is a frequency-converted component, and 30 is a component of the self-noise 21 of the limiter 7 passed through the band-pass filter 5 and output from the second mixer.

As described above, the power of the noise 30 is sufficiently small, and there is no problem that the output signal 14 of the feedback circuit affects the signal output from the second mixer 9.

Also, the group delay time of the bandpass filters 25 and 26 is t3
Then, the formula fi1. (21 is Δθ1-01(t) - θ1 (t-tl -t2-t3)...(1)'
Δθ2 θ1(t) - θ2 (t-tl -t2-t3)...(2)"
becomes. Here, since the band pass filters 25 and 26 have wide bands, t3 and t1 become t1, and together with the previous t24 and t3,
Δθ1. The condition that Δθ2 is sufficiently small is also satisfied.

In the above embodiment, the bandpass filter 25. of the bandpass filter 25. has a wide band enough to remove unnecessary waves output from the first mixer.
Although 26 has been connected to the output of the first mixer 3, 4, it could also be connected to the output of the limiter 7.8 or to the output of the bandpass filter 5.6.

Furthermore, the same effect can be obtained by replacing the bandpass filters 25 and 26 with trap circuits that remove the output signals of the feedback circuits.

In addition, in the above embodiment, a limit vine 7.8 having an amplification effect is used.
Although the configuration is shown using an amplifier, the same effect as in the above embodiment can be obtained even if this is replaced with an amplifier.

Further, even when the synthetic dipercussion receiving apparatus of the present invention is applied to a receiver using an intermediate frequency, the same effects as those of the above embodiments can be obtained.

Next, as an embodiment of the first invention of the present application, it is possible to omit the bandpass filters 25 and 26 in the embodiment shown in FIG. Since it is clear from the description of the embodiment, it will be omitted.

〔Effect of the invention〕

As described above, according to the present invention, the output signal from the first mixer is inputted from the amplifier to the second mixer through the bandpass filter.
Load noise in the system up to the mixer does not affect the signal output from the second mixer, and a wideband bandpass filter is provided to remove unnecessary waves output from the first mixer. 2nd wave caused by unnecessary waves
This has the effect of eliminating the influence on the output signal of the mixer.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a synthetic diversity receiving device according to an embodiment of the second invention of the present application, FIG. 2 is a block diagram of a conventional synthetic diversity receiving device, and FIG. 3 is a block diagram of a conventional synthetic diversity receiving device.
FIG. 4 is a diagram for explaining the problems that occur with the device shown in the figure, and FIG. 4 is a diagram for explaining that the problems of the conventional device are solved by the present invention. 1.2...Receiving antenna, 3.4...First mixer, 5.6...Band pass filter, 7.8...Limiter, 9.10...Second mixer, 11...・Synthesizer,
12...Band pass filter, 13...Limiter, 1
4...Output signal, 25.26...Band-pass filter with a wide band capable of removing unnecessary waves output from the first mixer, 40...Feedback circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts. Fig. 1 Fig. 2 Fig. 3 Fig. 3, m;it- Fig. 4 /W;/Di knee Jf&- Fig. 4, #fα- I7

Claims (2)

[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; an amplifier that amplifies the output signal from each of the first mixers; and each of the amplifiers. a narrow bandpass filter that is connected to the output of the amplifier and has a bandwidth that passes random phase components due to fading and the main component of the modulated signal contained in the output signal, and reduces self-noise of the amplifier; and the narrowband pass filter a second mixer that mixes the output signal of and each of the received signals, a combiner that combines the outputs of the second mixers, and a feedback circuit that feeds back the output signal of the combiner to the first mixer. A synthetic diversity receiving device characterized by: (2) 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; an amplifier that amplifies the output signal from each of the first mixers; and each of the amplifiers. a narrow band pass filter that is connected at a later stage and has a bandwidth that passes random phase components due to fading and main components of the modulated signal contained in the output signal of the amplifier, and reduces self-noise of the amplifier; an unnecessary wave removing means connected between the mixer and the second mixer for removing unnecessary waves output from the first mixer; and a third device for mixing the output signal of the narrow band pass filter and each of the received signals. 1. A combining diversity receiving device comprising: two mixers, a combiner that combines the outputs of the second mixers, and a feedback circuit that feeds back the output signal of the combiner to the first mixer.