SU1249597A1 - Device for measuring signal-to-noise ratio - Google Patents

Abstract

The invention relates to radio engineering and can be used to control the quality of a communication channel and to detect weak signals. The purpose of the invention is to increase measurement accuracy. The device contains a band-pass filter I, a limiter 2, a pulse generator 3, a recording unit 7, a pulse counter 8 and a recording unit 9, and a pulse generator 10. The introduction of drivers A and 5 time intervals, element 6 and the formation of new connections in the device eliminates the delay line, and does not impose any amplitude response on the amplifying path, since only phase relationships are used for the measurements. In addition, the measurement result does not depend on the magnitudes of the path gains and their nodes. 1 il. (/: with lN3 4 SO SP with

Description

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The invention relates to radio engineering and can be used in radio devices for measuring the signal-to-noise ratio, for monitoring the quality of a communication channel and for detecting weak signals.

The purpose of the invention is to improve the accuracy of measurements.

This goal is achieved in that the device for measuring the signal / tau ratio, containing a band-pass filter, whose input is connected to the device input, and the output - to the input of the limiter, pulse generator, pulse generator, and recording unit consisting of a series-connected pulse counter and the registering unit, with the installation input of the pulse counter connected to the output of the pulse generator, the sequentially connected first and second time formers and an AND element are entered, including between the output of the pulse former and the counting input of the pulse counter, the second input of the AND element is connected to the output of the pulse former, the input of which is with the output of the limiter.

The drawing shows a structural electrical circuit of the device.

The device for measuring the signal-to-noise ratio contains a series-connected band-pass filter 1, a limiter 2, a pulse shaper 3, a shaper 4 and 5 time slots, an AND 6 element and a registering node 7, consisting of a series of pulses connected in series 8 and a recording unit 9. The second (setting) the input of the counter 8 pulses connected to the output of the generator 10 pulses. The second input element And 6 is connected to the output of the imaging unit 3 pulses.

The device for measuring the signal-to-noise ratio operates as follows.

The input process voltage is passed through a band-pass filter 1, is limited until a voltage limiter 2 is obtained at the output, from which a short pulse, which coincides with the positive (or negative) fronts of the input pulses, is generated using the pulse shaper 3. Thus, the period following them is 495972

pulses at the output of the imaging unit 3 is equal to the current value of the period of the frequency f of the input process.

The spectral density of the instantaneous frequency W (f) depends on the parameter, f and the signal / noise ratio S, where f. - the rms width of the noise spectrum, determined by the characteristic of the input bandpass

10 filter. Since f is constant, the value of the spectral density at the frequency of the signal W (fj) is uniquely related to the value of S.

Pulses from the shaper output

15 3 start the time interval shaper, at the output of which a voltage drop of the desired sign appears (for example, negative) only if the duration

20 of the current period T exceeds the interval, / 2. The value of LT is related to a frequency band of l. by ratio

2

, LT |, f J, which is chosen from the condition fjj, where f, is the frequency

25 beeps.

This differential triggers a shaper of 5 time intervals, at the output of which an impulse of duration dT is formed, arriving at the input of element AND 6. The second input of element 6 is directly fed to the day impulse from the output of shaper 3 (its duration is significantly shorter).

35

If the pulses at the inputs of the element

And 6 coincide in time, what happens under the condition

T + iTj / 2T T - Tr / 2,

40, at the output of the element AND 6, a pulse appears, which is registered by counting. 8 pulses.

To the installation input of the counter 8 short pulses arrive, next 45 with intervals T, from the generator output 10 pulses. Counter 8 during the interval T counts the input I1 pulses. At the end of the interval T., the result of the leading edge of the next 50 pulse of the generator of the 10 pulses is recorded in the counter memory, and the falling edge of this pulse of the counter 8 is set to the initial state. The result is registered

55 is controlled by block 9 and is determined by the ratio

(f) .T.f; - -. (one)

Since f is fixed, and the values of aTj and Tc can be specified with precise precision, the value of N depends only on W (f,), i.e. It is uniquely associated with the signal-to-noise ratio and characterizes it with high accuracy.

Thus, the introduction of two timers and the element I into the device and their corresponding inclusion can significantly improve the measurement accuracy, since the values of Tu and lT, on which the instrument reading N is, can be maintained with the accuracy of a quartz oscillator.

In addition, in comparison with the known, the proposed device has a significantly larger dynamic range D, which is defined as follows.

The smallest reading of the device N is determined when, at which W (f,) 0.5, The highest value of N ..

is at a ratio of

 As a result, the value of the dynamic range of the instrument can be found by the formula

.

(2)

From the expression (2) it follows that with decreasing dT one can get any necessary value of D.

An increase in D leads to an additional increase in the measurement accuracy in comparison with the known device, since the working part of the scale of the instrument is stretched, as it were, many times.

Editor I. Derbak Order 4334 / 5A

Compiled by N.Mikhalev

Tehred L. Serdyukov Proofreader E. Sirohman

Circulation 728 Subscription VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, st. Project, 4

2495974

Compared with other well-known devices, the measurement accuracy in the proposed device is higher due to the fact that there are no 5 delay lines at all, and the result does not depend on the magnitudes of the gains of the paths and their nodes.

In addition, in the proposed device. No requirements are imposed on the amplitude response of the amplifier path, since only phase relationships are used for the measurements. This makes the device much simpler. At the same time, unlike the known ones, the proposed device does not require any adjustment.

Claims (1)

Invention Formula A device for measuring the signal-to-noise ratio, which contains a bandpass filter, whose input is connected to the device input, and the output - to the limiter input, a pulse shaper, a pulse generator, and a registering node consisting of a series-connected pulse counter and a recording unit; impulses connected to the output of the impulse generator, characterized in that, in order to increase the measurement accuracy, the first and second time and / or serializer are connected in series th interval and the AND gate, connected between the output of the pulse shaper and pulse counting input of the counter, the second input of AND gate is connected to the output of the pulse shaper having an input coupled to an output limiter.