SU1660199A2 - Signal demodulator - Google Patents

Abstract

The invention relates to radio communications, and is intended primarily for work on the tropospheric radio channels of the millimeter wave range. The purpose of the invention is to improve the noise immunity under the conditions of varying the magnitude of the phase dispersion of the signal. To achieve this goal, an adder 10, a nonlinear converter 11, a comparator 12, and a delay line 13 with taps are entered into the demodulator. The newly introduced blocks make it possible to estimate the signal-to-noise ratio and, taking into account the current phase dispersion, the switch 4 of the signals is set to provide the best noise immunity for these conditions. 1 il.

Description

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The invention relates to radio communications and is intended primarily for work on tropospheric radio channels of millimeter wave range,

The purpose of the invention is to increase the noise immunity of a signal demodulator under conditions of a change in the magnitude of the phase dispersion of the signal and the signal-to-noise ratio.

The drawing shows a structural electrical circuit of a signal demodulator.

The signal demodulator contains analyzer 1, carrier recovery block 2, input filter 3, signal switch 4, multiplier S, delay line b, integrator 7, clock synchronization block 8, decision block 9, adder 10, nonlinear converter 11, comparator 12 and line 13 delays with taps.

The signal demodulator operates as follows.

The input of the demodulator is affected by an additive mixture of signal and white noise:

U (t) A COS fttet + #t) + fb + | (t), where A is the signal amplitude;

Odo - circular frequency signal;

p (t) is phase changing;

ro - instantaneous initial phase;

§ (t) - making noise.

The mixture of signals U (t) is fed to the signal input of the analyzer 1: to the input of the carrier recovery unit 2, to the input of the input filter 3 and to the input of the delay line 13 with taps. The signal U (t), having passed the input filter 3 (the bandwidth of which is wide enough compared to 1 / T), is fed to the input of multiplier 5 and the input of the delay line b, which passed through, delayed per clock, signal U (t-7) A COS fflb (tT) -f tft-T) + po + 4-(1-1),

comes next to the first input of the switch 4 signals.

From the carrier recovery unit 2, the reference oscillation G (t) A COS (ftfet 4- $) is fed to the second input of the switch A of the signals and to the reference input of the analyzer 1. The analyzer 1 (working according to the same algorithm as in the prototype) produces a voltage UA - 1 if there are frequency selective fading on the path of radio wave propagation. In the absence of fading, the signal UA 0 is produced. The signal from the output of the analyzer 1 is fed to the control input of the switch 4 signals. At the same time, the signal U (t) is fed to the input of the delay line 13 with taps and from the corresponding taps to the inputs of the adder 10, s which will generate the statistical values A {U (t) affecting the nonlinear converter 11, with the characteristic L / (L). The signal at the output of the nonlinear converter 11 will be proportional to Vh2 (A). . A comparator 12 from the received signal will generate a signal UK 1 if the amount of radiation on the propagation path is significant and

h 10, With the amount of radiation on the track

spread insignificant and

 the output of the comparator 12 will form a voltage of UK 0.

The signal UA from the output of analyzer 1 is fed to the control input of the switch 4 signals, and the UK signal from the output of comparator 12 to the additional (control) input of the switch 4 signals. In this case, in the switch A of signals, the signals UA and UK are compared by logical multiplication, i.e. the resulting voltage U 1, if UA UK 1. in all other cases, U 0. Control voltage U 1 translates the comparator 4 signals into the autocorrelation mode of operation. In this case, the signal U (t-T) from the first input of the switch 4 signals will go to the reference input of the multiplier 5. The product of the signals U (t) and U (t-T) is integrated in the integrator 7, at the output

which will be the result:

Lt And f / jAcosluJbt) + (+ Ј (t)} x

(n - i)

x (t-T) +) + po H- Ј (

- 0.5 A2 T cos) - + fl + & + 9h- In the subsequent decisive block 9, synchronized by the block 8 clock synchronization, decides on the value and sign I.

The control voltage U 0 translates the switch 4 signals into a coherent mode. In this case, the signal G (t) from the second input of the switch 4 signals will go to the reference input of the multiplier 5. The product of the signals U (t) and G (t) is integrated into the integrator 7, the output of which will be the result: ht I ,. JA COS ft) 0t + p (t) y X

(L

xA cos (ufe t +) dt 0.5 A2T cos p + c.

The decisive block 9 (as in the first case) decides on the value of the h sign on the value of the received signal. Thus, the proposed signal demodulator estimates not only the phase dispersion value, and hence the effect of frequency-selective fading, but also The h2 signal-to-noise ratios, and, consequently, the effect of radiation, thereby selecting a more optimal mode and increasing the noise immunity of the demodulation of an extremely high-frequency signal transmitted through the turbulent troposphere.

Claims (1)

Claims of the invention Signal demodulator according to aut. St. No. 1540029, characterized in that, in order to increase the noise immunity under the conditions of variation of the variance value 0 Signals of the signal and signal-to-noise ratio, a series-connected adder, a non-linear converter and a comparator, and delay lines with taps, the corresponding terminals of which are connected to the inputs of the adder, the comparator output connected to the auxiliary input of the signal switch, and the input of the delay line with taps with the input of the demodulator.