JPH0336823A - Diversity reception circuit after detection - Google Patents

Abstract

PURPOSE:To realize a circuit comprising a single series AGC circuit and a detector and to simplify the circuit constitution by using a frequency conversion means so as to convert reception signals received by plural antennas into a frequency region not overlapped with each other, and synthesizing them. CONSTITUTION:Signals A1(t), A2(t) of a frequency fC received by plural antennas 21, 26 are inputted respectively to mixers 23, 28 and mixed with signals of local oscillation frequencies fL1, fL2 outputted from local oscillators 22, 27 and signals of frequencies (fIF- f), (fIF+ f) are inputted to a synthesizer 25 via BPFs 24, 29. The output of the synthesizer 25 is a synthesizing signal (A1+A2) having two frequency components, amplified by one AGC circuit 40, detected by one synchronization detector 50 and subject to diversity synthesizing 59.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a post-detection diversity receiving circuit that detects and then combines a plurality of received signals in diversity reception of wireless communication.

[Conventional technology]

Guibersich reception is a multiplex reception synthesis technique that combines multiple received signals with little correlation to relieve fluctuations in the received electric field in order to reduce the effects of multipath fading, rain attenuation, and the like.

FIG. 6 is a diagram showing the configuration of a conventional two-branch detection post-diversity receiving circuit.

In the figure, a first antenna 81. The signal AH(t) of frequency fc received by mixer 83. The signal is input to the oscillator 82, is mixed with a signal having a local oscillation frequency fL which is the output of the local oscillator 82, and is extracted as a signal having an intermediate frequency flF via a band pass filter (hereinafter referred to as rBPFJ) 84I. The output of BPF841 is an automatic gain adjustment amplifier (r
(referred to as "AGC circuit") 85. is amplified. This amplified output is sent to the synchronous detector 86. is input to the local oscillator 87, and is detected by a signal having the same frequency as the intermediate frequency rap output from the local oscillator 87 and whose carrier phase is not synchronized. This detection output is the in-phase component amplitude 11(t) and the quadrature component amplitude Ql(t) of the signal received by the first antenna 81□. Second antenna 81. The signal Az(t) received at
Similarly, mixer 83□, BPF84□, AGC circuit 8
5□, the in-phase component amplitude 12 (t
) and the orthogonal component amplitude QzD).

When the diversity combining circuit 89 performs maximum ratio combining in which the detection outputs weighted in proportion to each carrier-to-noise ratio of a plurality of received signals are added and combined so that the carrier-to-noise ratio is maximized. , the in-phase component amplitude 1(t) and the quadrature component amplitude Q(t) are 1 (t) −a, (1, cos θ1 − b, sin θ1
)+a2(12cosθ2−Q2sinθ2)---
−−−−−−(t)Q(t)−a, (1, sinθ, +
Q, cos θ1) + ax(Izsinθz+Qzco
sθ2 ) ”-”'-”'-' (2) is synthesized.

Here, the coefficients a, , az are respectively antenna 81.8
It is a value proportional to the square value of the carrier-to-noise ratio of 8. In addition, θ and θ2 are complex numbers (1+ J Q +), (
+2 +J
) θ2−−θ2 , −−−−−−−−
- There is a relationship shown in (4).

FIG. 7 shows the same 1υ1 detector 86. It is a figure showing an example of composition (quadrature detector).

In the mixers 104 and 106, the output signal of the AGC circuit 85 inputted from the 3y:4i child 101,
The output signal of the local oscillator 87 input from 3 (frequency f
IF) are combined. However, the output signal of the local oscillator 87 inputted to the mixer 106 is
05 and is transferred and summed by π/2. Low-pass filters (hereinafter referred to as rLPF) 107 and 108 extract the Haesband relative portions of the in-phase component amplitude i (t) and the quadrature component amplitude q (t) from each output signal of the mixer 104 and 106, respectively.

In the configuration shown in FIG. 7, the in-phase component amplitude t(L) and the quadrature component amplitude q(t) are converted to
The signal is converted into a digital signal and output to the diversity combining circuit 89.

[Problem to be solved by the invention]

In the above-mentioned post-detection diversity receiving circuit, the signals A+(t) and Az(L) input to the ACC circuit have large fluctuations of, for example, about 50 (dB) due to fading. Therefore, in the AGC circuit, it is necessary to linearly amplify the human input signal that fluctuates greatly and to increase the dynamic range in order to maintain the output at a constant level, making it difficult to design and adjust the circuit as an analog circuit.

Furthermore, an independent detector corresponding to each received signal is required before diversity combining, resulting in an increase in the overall size of the circuit.

The present invention is intended to solve these problems,
It is an object of the present invention to provide a post-detection diversity receiving circuit that can be realized using one series of AGC circuits and a detector.

[Means to solve the problem]

FIG. 1 is a principle block diagram of the post-detection diversity receiving circuit of the present invention.

In the figure, in a post-detection diversity receiving circuit that performs diversity synthesis after amplifying and detecting each received signal received by a plurality of antennas, a frequency conversion means that converts each received signal to a frequency domain in which the signal spectra do not overlap with each other, and A synthesizing means for synthesizing the frequency-converted signals of the signals into one synthesized signal, an automatic gain adjustment amplifying means for amplifying the synthesized signal, and detecting the amplified synthesized signal with a predetermined signal corresponding to each frequency domain. Features [Function] The received signals received by the plurality of antennas are converted by the frequency converting means into frequency regions that do not overlap with each other, and the receiving signals are converted by the frequency converting means into frequency regions that do not overlap with each other. is synthesized with At this time,? Since the received signals of j[ are in frequency regions that do not overlap with each other, they are combined without interfering with each other. This composite signal is one signal having a plurality of frequency components, is amplified as it is by the automatic gain adjustment amplification means, and is input to the detection means.

The detection means extracts a detection output corresponding to each received signal from a plurality of frequency components.

That is, by converting a plurality of received signals into a frequency domain that does not overlap with each other, detection outputs corresponding to the plurality of received signals can be extracted using the l-series automatic gain adjustment amplification means and detection means, and in the same manner. Diversity synthesis is possible.

〔Example〕

FIG. 2 is a block diagram showing the configuration of an embodiment of the present invention.

In the figure, a signal A received by the first antenna 21,
(t) is manually input to the mixer 23. The mixer 23 is
This signal is mixed with a signal of local oscillation frequency rt+ output from local oscillator 22. The output of the mixer 23 is B
It is manually input to the synthesizer 25 via the PF 24. Also, the second
The signal Az(u) received by the antenna 26 of
28. Mixer 28 mixes this signal with a signal of local oscillation frequency fL2 output from local oscillator 27. The output of the mixer 2 is input to the combiner 25 via the BPF 29.

The output of the synthesizer 25 is 3tJ via the AGC circuit 40.
The mixer 51 and mixer 52 of the l-detector 50 are manually powered.

The mixer 51 receives the local oscillation frequency Cf from the local oscillator 53.
.
/2 phase shift 2S54.

The outputs of mixers 51 and 52 are each branched into two branches, one of which is connected to A/D converters 56 and 58 via LPFs 55 and 57.
The other input is input to the A/D converter 64.66 via the BPF 63.65.

Output 11 (t
), Q+(t), IzD), and Q2(t) are input to the diversity combining circuit 59 as detection outputs of the synchronous detector 50.

Here, the correspondence between FIG. 1 and FIG. 2 will be explained.

The frequency conversion means includes a local oscillator 22, a mixer 23, and a BP
Corresponds to F24, local oscillator 27, mixer 2, and BPF29.

The combining means corresponds to the combiner 25.

The automatic gain adjustment amplification means corresponds to the AGC circuit 40.

The detection means corresponds to a synchronous detector 50 including a local oscillator 53.

The antennas 21 and 26 and the diversity combining circuit 59 shown in FIG. 2 are the same as the corresponding parts of the conventional Daihar Sochi receiving circuit.

The operation of the embodiment will be described below.

Signal AI of frequency fc received by first antenna 21
(t) is mixed with a signal of local oscillation frequency f, and B
A signal with a frequency (r+F-Δr) is extracted via the PF 24. Similarly, the signal A2(t) of frequency fc received by the second antenna 26 is sent to the mixer 28 and the BPF 29.
A signal of frequency (r IF + Δr) is extracted via the .

The frequency-converted signals are combined in a combiner 25. FIG. 3 is a diagram showing the frequency spectrum of the composite signal. In the figure, the horizontal axis shows the frequency, the vertical axis shows the signal level of each frequency-converted signal, and A1 is BPF2
A2 corresponds to the frequency (f+rAf) (7) signal output from BPF29, and A2 corresponds to the frequency (f+F) signal output from BPF29.
+Δf).

The AGC circuit 40 is manually supplied with a composite signal (A, 10A2) having two frequency components as shown in FIG.
amplified.

FIG. 4 is a diagram showing the configuration of the AGC circuit 40.

In FIG. 4, the AGC circuit 40 amplifies the manually input composite signal (A I+A 2 ) and outputs the output signal (Ant
+AQ2), a square law detector 43 and an LPF 45, which obtain a gain control voltage (6) for the amplifier 4I from this output signal.

FIG. 5 is a diagram showing fluctuations in received signal level due to fading. In the figure, the vertical axis shows the received signal level, and the horizontal axis shows time. The solid line represents the square value A,+2 of the received signal level of the first antenna 21, the thin dotted line represents the square value lA212 of the received signal level of the second antenna 26, and the dotted line represents the sum of the square values of each signal level ( IAI 12+ lA
21”).

Gain control obtained from the output signal (Ant + AO2) of the AGC circuit 40? ff1l voltage ■6 is Vc = 1A
O112 + 1AOZl - (s), and amplifier 4
The gain G of 1 is approximately as follows.

Note that since the numerator is approximately constant, the gain G changes in accordance with changes in the denominator.

In the conventional circuit shown in FIG. 6, for example, the AGC circuit 8
5. The gain G1 is as follows, and its denominator lA112 is 5 as shown in FIG.
There is a fluctuation of about 0 (dB). In order to keep this fluctuation constant, the AGC circuit 85I required a wide dynamic range of about 50 dB:1.

Further, the same was true for the AGC circuit 85□.

However, in this embodiment, the AGC
The variation in human care health of circuit 40 is IAl+2 1A212
is smaller than when it fluctuates independently. That is, (6
) The fluctuation in the denominator (IA112+lA2+2) of the equation is small, and the dynamic range of the AGC circuit 40 can be made smaller than conventionally.

The signal amplified by the AGC circuit 40 is detected by a synchronous detector 50. In this synchronous detector 50, by mixing with the local oscillation frequency (foF-Δr) signal (one phase shifted by π/2), the signal from the LPF 55.57 to the first antenna 21 is
The in-phase component amplitude 1 + (t
) and the orthogonal component amplitude Q, (L) are output. On the other hand, 2
Second antenna 2 from BPF63.65 tuned to Δf
The in-phase component amplitude 1zD of the signal A2(t) received at 6
) and the orthogonal component amplitude Q2(t) are output.

However, this in-phase component amplitude 1z(t) and quadrature component amplitude Q
Since z(t) rotates at an angular frequency of 2π (2Δf), θ of the diversity combining circuit 59.

Add -4πΔf to , stop the rotation, and synthesize.

That is, the operation of the diversity combining circuit 59 shown in equations (1) and (2) is as follows by replacing θ2 with (θ2−4πΔr), and 1(L)=a+(Itcosθ′Ω,sinθI)+
az(Izcos(θ 2−4π Δf)−Qzsi
n(θ 2-4π Δf)) (8) Q(t)=a+ (1, sin θ1+mouth, cos θ1)
+ az(Izsin(θ2−4πΔf)+QzcoS
(θ2−4πΔf)) (9) It becomes.

In this way, the signals received by the two antennas 21 and 26 are converted into different frequency domains, combined, amplified by one AGC circuit 40, detected by one synchronous detector 50, and then -Synthesized.

[Effects of the Invention] As described above, according to the present invention, the post-detection diversity receiving circuit can be constructed using the automatic gain adjustment amplifier and the wave detector of the (1) series, so that the circuit configuration can be simplified.

In addition, by using a composite signal of multiple received signals,
Since the accuracy of the AGC circuit with respect to fluctuations in the received signal level can be reduced, the design and adjustment of the AGC circuit becomes easier.

In this way, the structure and design are simplified and miniaturization is possible, so it can be applied to a receiver for mobile communication.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the principle of the present invention. FIG. 2 is a block diagram showing the configuration of the embodiment. FIG. 3 is a diagram showing the frequency spectrum of the composite signal. FIG. 4 is a diagram showing the configuration of the AGC circuit. FIG. 5 is a diagram showing fluctuations in received signal level due to fading. FIG. 6 is a diagram showing the configuration of a two-branch detection Da.f. Haschi receiving circuit. FIG. 7 is a diagram showing the configuration of a synchronous detector. 21.26.81...Antenna 22.27.53.82.87...Local oscillator 23.
28.5 l, 52.83, 104, 106...Bone consolidator 24, 29, 63, 65, 84...BPF25
...Synthesizer 40.85...AGC circuit 41...Amplifier 43...Square detector 45.55.57...LPF 50.86...Synchronized detector 54.106... Phase shifter 56.58.64.66.109.110...A/D
Converter 59.89...Diversity synthesis circuit

Claims (1)

[Claims] (1) In a post-detection diversity receiving circuit that performs diversity synthesis after amplifying and detecting each received signal received by a plurality of antennas, a frequency conversion means that converts each of the received signals to a frequency domain in which signal spectra do not overlap with each other; combining means for combining the frequency-converted signals of each received signal into one composite signal; automatic gain adjustment amplification means for amplifying the composite signal; and detection of the amplified composite signal with a predetermined signal corresponding to each frequency domain. and a detection means for extracting a detection output corresponding to each of the received signals.