SU987785A1 - Device for measuring signal-noise ratio - Google Patents

Description

(B) DEVICE FOR MEASURING RELATIONSHIPS

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The invention relates to a radio measuring technique and can be used in monitoring channels with noise-like signals.

A known device for measuring the signal-to-noise ratio containing an inverter connected in series, the first adder, the weight filter, the noise detector and the signal-to-noise ratio calculator, to the other of which the output of the signal detector t1 X is connected

However, the known device has a low accuracy of measuring the signal-to-noise ratio in discrete channels with noise-like signals.

The purpose of the invention is to improve the accuracy of measuring the signal-to-noise ratio of k discrete channels with noise-like signals.

This goal is achieved by the fact that in the device FOR: measurement. signal-to-noise ratio containing after signal / noise

the inverter, the first adder, the weight filter, the noise detector and the signal-to-noise ratio calculation unit, to the other input of which the output of the signal detector is connected, the first and second band-pass filters, the correlation receiver consisting of the first multipliers and narrow-band filters, the second adder and shaper noise-like

“0 signal containing the second multipliers and the third adder, while the output of the first bandpass filter is connected to the second input of the first adder and the first inputs of the first multipliers 15, whose outputs are connected to the corresponding inputs of the second adder and to the first inputs of the second multipliers through one of the filters , the output of the second multipliers

20 is connected to the corresponding inputs of the third adder, the iratoporo output is connected via the second bandpass filter to the inverter input, the output 398 of the second adder is connected to the input of the signal detector, and the second inputs of the first and second multipliers receive a pseudo-random video sequence copy generator. The drawing shows a structural electrical circuit of the proposed device. A device for measuring the signal-to-noise ratio contains; the first and second bandpass filters 1 and 2, respectively, the first and second adders 3 and, respectively, the correlation receiver 5, consisting of the first multiplier 6 and narrowband filters 7, inverter 8, weight filter 9, noise detector 10, calculation block 11 the signal-to-noise ratio, the detector 12 of the signal and the shaper 13 of the noise-like signal, consisting of the second multipliers And and the third adder 15. The device operates as follows. The device receives an additive, a mixture of a useful broadband noise-like signal and white noise. After filtering, a noise-like signal whose spectrum occupies a band equal to the band of the main lobe of the spectrum of the output signal of the first band-pass filter 1 is fed to the first input of the first adder 3 and the correlation receiver 5 to the control inputs of which, respectively, copies of pseudorandom video sequences of signals of units and zeros are received. As a result of the correlation processing, monochromatic signals separated in time in accordance with the alternation of information signals of units and zeros are fed to the inputs of the second adder and to the inputs of the second multipliers T of the imaging unit 13 of the noise-like signal. The latter, together with the second band-pass filter 2, generates a copy of the received noise-like signal, which is practically free of additive noise. From the output of the second band-pass filter 2, the noise-like signal through the inverter 8, which changes the phase of the high-frequency oscillations to the opposite one, is fed to the second input lution of a useful regular noise supportive signal and accumulation of additive noise noise. the output of the first adder 3, the noise pressure through the weight filter 9, which gives the envelope of the comb characteristic a kind of weight function, is applied to the noise detector 10 with a quadratic characteristic. From the noise detector TO, the effective voltage of the minds is fed to the first input of the signal-to-noise ratio calculation unit 1, and the second input of which from the output of the signal 12 is supplied to the effective voltage of the signal. From the operation of the device it can be seen that the value of the signal-to-noise ratio is equal, PC is the power of the useful signal; f is the spectral density of hell (Surround noise. Ac1p is the bandwidth of a narrowband filter. Since for communication systems with noise-like signals, it is always :- the condition that the bandwidth of the main lobe of the spectrum of a noise-like signal and Fiatrc is significantly greater than the filter bandwidth of the correlation receiver, and in our servants of tea 4f hf1. Then the magnitude of the methodical error of the proposed device is determined by the value of the ratio Uhf / Lff. The evaluation of the accuracy of the control of the signal-to-noise ratio when using the proposed device is the value of PC. 4mtcr - Pi, tT where pit is the number of elements in the M sequence. The value of B is a complex value that directly depends on the true value of the signal-to-noise ratio at the channel input and on the correlation link. between M sequences of parcels zero and one.

Thus, with the introduction of a first and second bandpass filters, a correlation receiver, a second adder and a noise-like signal generator, the accuracy of monitoring the signal-to-noise ratio in communication systems with noise-like signals by eliminating the possibility of penetration of a useful signal about the separation channel and the formation of an effective voltage by a considerable amount.

At the same time, the control accuracy is higher, the higher the true value of the signal-to-noise ratio at the input of the transmission channel.

Claims (1)

1. USSR author's certificate Vf 399081, cl. H Oil B 7/02, 1973. F one one I j L.