JPH01151323A - Synthetic diversity receiver - Google Patents

Abstract

PURPOSE:To prevent distortion from being generated in the demodulated output of a detector by providing attenuators between two amplifiers and between two second mixers, respectively. CONSTITUTION:The attenuators 21 and 22 are provided at the output of the amplifiers 11 and 12. When reception signals are inputted from reception antennas 1 and 2 to the second mixers 13 and 14 via RF amplifiers 3 and 4, and power distributors 5 and 6, the levels of the output signals from the amplifiers 11 and 12 are set at low levels even when the levels of the reception signals exceed the dynamic ranges of the second mixers 13 and 14, therefore, spurious in the neighborhood of the desired output signals of the second mixers 13 and 14 can be suppressed sufficiently at minimum levels compared with the desired output signal, or no spurious is generated. In such a way, no distortion can be generated in the demodulated output of the detector.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a receiving device for a communication device used in an environment where fading exists, and in particular, the present invention relates to a receiving device for a communication device used in an environment where fading exists. This invention relates to a combining diversity receiving device that combines received signals of 2 in phase.

[Conventional technology]

FIG. 2 shows a conventional synthetic diversity receiver disclosed in, for example, Japanese Patent Laid-Open No. 57-125536. In the figure, 1.2 is a receiving antenna, 3.4 is an RF amplifier, and 5.
6, 17.19 is a power divider, 7.8 is a first mixer that takes the difference frequency, 9.10 is a narrow band pass filter, 11
．． 12 is an amplifier, 13.14 is a second mixer that takes the difference frequency, 15 is a combiner, 16 is a bandpass filter, 18
is a limiter, and 20 is a detector. Further, 30 is a feedback circuit, and a band pass filter 16. Power divider 17, limiter 18. It is composed of a power divider 19.

Next, the operation will be explained.

The received signal of receiving antenna 1.2 is calculated by the following formula (%). However, AI(t) and At(t) are for receiving antenna 1.2.
, fc is the carrier frequency, θ(1) is the modulation signal, θ1. θ2 is a random phase due to fading.

Each received signal is sent to RF amplifiers 3, 4 and power divider 5.
, 6, the first mixer 7.8, the second mixer 13.
14. The output signal of the power divider 19 of the feedback circuit 30 is expressed by the following equation.

cos(2πfot+φ(t)) −
(3) fo is the center frequency of the bandpass filter 16 of the feedback circuit 30, and φ(1) is the phase to be determined later.

Each received signal and the signal from the feedback circuit 30 are frequency-mixed in the first mixer 7.8. Since the first mixer 7.8 takes the frequency component of the difference, its output 1g is expressed by the following equation.

IAA+(t)cos(2rt frtt10<1)+
θ1-φD))・(4)%Az(t)cos(2rt
fret+θ(1) +θ2-φ(t) ) ・f
5) However, f, ,=fc−f.

The output signal of the first mixer 7.8 passes through narrow band pass filters 9 and 10 and amplifiers 11 and 12, and becomes a signal expressed by the following equation.

! 4CA+(t)cos(2rt LtL+θ+)
−(61% CAt(t)cos(2rc frrt
+θz) −(7, where C is the amplifier 11.12
is the gain.

In the second mixer 13.14, the signal of equation (61, +71) and the received signal from the receiving antenna L, 2 are frequency-mixed, and the second mixer 13.1 takes the difference frequency component.
The output signal from 4 is given by the following equation.

'A CA +”(t) cos (Z rc fat
+θ(t)) ・(81'A CAt"(t)cos
(2rc fat 10(t)) −+91 formula (81
, (9), the output signals of the second mixers 13 and 14 have random phases θ1. It is found that θ2 is not included, and therefore, the received signals are combined in the same phase in the combiner 15. The output signal of the synthesizer 15 is passed through a bandpass filter 16. Power divider 17, limiter 18. Via the power divider 19, it is fed back to the first mixer 7.8. Since the signal to be fed back must be equal to equation (3), φ
(t)=θ(1) ・・・αυ
Therefore, the feedback phase φ(1) is equal to the modulation signal of the received signal. Further, the output signal of the power divider 17 is demodulated by the detector 20.

[Problem that the invention seeks to solve]

Since the conventional composite diversity receiving device is configured as described above, the received signal from the receiving antenna 1.2 is input to the second mixer 13.14 via the power divider 5.6, where it is input to the second mixer 13.14. However, the signal level from the amplifier 11.12 is near the saturation level of the amplifier 11.12, and the received signal from the receiving antenna 1.2 is mixed in frequency with the signal from the second mixer 13.14. If the signal is input to the second mixer 13.14 at a level exceeding the dynamic range of the second mixer 13.14, many spurious components will be generated from the second mixer 13.14.

Among these spurious components is the second mixer 13.1.
There is a lot of noise in the vicinity of the frequency of the desired signal output from 4. Since such spurious components are not removed by the bandpass filter 16, they appear as distortion in the demodulated output of the detector 20.

The above problem will be explained using a specific example. carrier frequency 'f
c = 55.7 MHz, frequency f o of the output signal of limiter 18 = 10.7 MHz, narrow band pass filter 9
．． 10 center frequency f IF=45M)12. Since the first mixer 7 takes the difference frequency, the first mixer 7
The frequency of the output signal is 45 MHz. This desired signal passes through a narrow band pass filter 9 and is amplified by an amplifier 11. Due to this amplification effect, when the 45MHz signal level reaches the saturation level of the amplifier 11, the 55MHz, 7MHz
If the received signal of z exceeds the dynamic range of the second mixer 13, the desired signal frequency 1 is
0.7 MI (many spurious components occur in addition to z. The spurious component near the desired signal output from the second mixer 13 is 4x far-3x fc =
12.9 (MHz). This spurious component is input to the band pass filter 16. “IEEE Transactions on Communications” (IEEE Trans, On COM, Vo.
l, C0M-22, No, 8.1974゜pp, 10
Halpern (99-1106)
According to the paper of rn), the bandpass filter 1 of the feedback circuit
The bandwidth B+ of 6 must satisfy the condition B, >>Bo...@ with respect to the bandwidth B0 of the received signal.

Now, considering the FM broadcast wave and assuming that Bo is -270 KHz, B1 must be much wider than 270 KHz. However, since the 12.9 MHz spurious component is near 10.7 M)lz, it is not attenuated by the bandpass filter 16, or even if it is attenuated, it is not attenuated sufficiently. Therefore, it appears as distortion in the demodulated output of the wave detector 20.

The present invention has been made in order to improve the above-mentioned drawbacks of the conventional ones, and is to provide a composite diversity reception system in which spurious signals near the desired frequency outputted from the second mixer 13 and 14 do not cause distortion in the wave detector 20. The purpose is to obtain equipment.

[Means for solving problems]

The combined diversity receiving device according to the present invention includes an amplifier 1
An attenuator is provided for the output of 1.12.

[Effect]

In the combined diversity receiving device of the present invention, when the received signals from the receiving antennas 1 and 2 pass through the RF amplifier 3.4 and the power divider 5.6 and are input to the second mixer 13.14, the level thereof is Even if the dynamic range of the second mixer 13.14 is exceeded, the level of the output signal from the amplifier 11.12 is lowered by the attenuator, so the spurious near the desired output signal of the second mixer 13.14 is reduced to the desired output signal. It is either sufficiently low compared to the above, or it does not occur at all.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a composite diversity receiving apparatus according to an embodiment of the present invention, and in the figure, the same reference numerals as in FIG. 2 indicate the same parts. In this embodiment, attenuators 21 and 22 are provided at the outputs of amplifiers 11 and 12.

The operating principle of the present invention will be explained. The operating principle is the same as in Fig. 2, but the output signal of the first mixer 7.8 is sent to the amplifier 11.
．． 12 to the saturation level of amplifier 11.12, the level is lowered by attenuator 21.22. Therefore, as in the conventional example, the carrier frequency f c = 55
．． 7M1 (the level of the received signal of z is the second mixer 13.
Even if the dynamic level is higher than the dynamic level of 1-4, the 12.9 MHz spurious component near the desired output signal frequency 10.7 MHz of the second mixer 13.14 does not occur, or the level is sufficiently low compared to the desired signal level. Become.

Therefore, no distortion appears in the demodulated output of the detector 20.

〔Effect of the invention〕

As described above, according to the composite diversity receiving device according to the present invention, since the attenuator is provided at the output of the amplifier, even if the received signal from the receiving antenna exceeds the dynamic range of the second mixer, Since the spurious components near the desired signal of the two mixers are sufficiently low or do not occur at all, they can be sufficiently removed by the bandpass filter of the feedback circuit. Therefore, even if the reception level is high, this combined diversity method is possible.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of a synthetic diversity receiving apparatus according to the present invention, and FIG. 2 is a diagram showing an embodiment of a conventional synthetic diversity receiving apparatus. In the figure, 1.2 is a receiving antenna, 3.4 is an RF amplifier, 5, 6, 17.19 is a power divider, 7.8 is a first mixer that takes the difference frequency, and 9. 10 is a narrow band pass filter, 11.12 is an amplifier, 13.14 is a second mixer that takes the difference frequency, 15 is a synthesizer, 16 is a band pass filter, 18 is a limiter, 20 is a detector, 21.22 is a The attenuator 30 is a feedback circuit.

Claims (1)

[Claims] (1) A first system that mixes received signals from at least two or more antennas and a signal from a feedback circuit, which will be described later.
a mixer, a bandpass filter connected to the output of each of the first mixers, an amplifier that amplifies the output of each of the bandpass filters, and a first mixer that mixes the output signal of each of the amplifiers with the received signal. 2 mixers; a combiner for combining the output signals of each of the second mixers; and a feedback circuit having a bandpass filter connected to the output of the combiner and a limiter connected to the output thereof. A receiving device comprising: an attenuator between each of the amplifiers and each of the second mixers.