SU444334A1 - Device for measuring the intensity of the noise signal in the background of impulse noise - Google Patents

Description

one

The invention relates to radio engineering, in particular to measurements in radio astronomy.

A device is known for measuring the intensity of a noise signal received against a background of impulse noise, based on the principle of finding a voltage level at which the number of intersections of the envelope of a mixture of a noise signal and impulse noise of this level is maximum.

The known device contains a detector around, connected to the signal input of a two-sided limiter, one of the outputs of which is connected to a recording unit, and an electric motor, one winding of which is connected to another output of the two-sided limiter through a pulse counter. Another motor winding is connected to an alternator connected to the control input of the two-sided limiter. The motor shaft is mechanically coupled to a double-sided potentiometer.

However, with a rapid decrease in the intensity of the noise at the input, the system may tune to a second maximum due to impulse noise. In addition, in the known device, the initial threshold of limitation is constant. At the same time, it is necessary that the initial limit threshold be less than the minimum measured noise signal.

However, with a rapid increase in the intensity of the noise signal, the sensitivity of the control system may be insufficient to trigger it.

The purpose of the invention is to expand the dynamic range and eliminate the possibility of tuning to a false maximum.

This is achieved by the fact that in the proposed device between the envelope detector and

the signal input of the double-sided limiter is connected to the limiter with the following threshold, which is connected by output through a low-pass filter with another control input of the two-sided limiter.

The drawing shows the block diagram of the device.

The envelope detector 1 is connected through limiter 2 to the next threshold with the signal input of double sided limiter 3,

one of the outputs of which is connected to the registering unit 4. The electric motor 5 is connected by one winding through a pulse counter 6 and an amplifier 7 to another output of the two-way limiter 3, and the other winding is connected to the output of the alternator 8 connected to the control input of the two-sided limiter 3 The motor shaft 5 is mechanically coupled to the potentiometer 9 of the two-sided limiter.

3. The output of limiter 2 with the following threshold is connected through a low-pass filter 10 to another control input of two-sided limiter 3.

The device for measuring the intensity of the noise signal against the background of impulse noise is based on the principle of finding the voltage level at which the number of intersections of the envelope of the received mixture of this level is maximum. This method of measurement in the presence of non-overlapping impulse noise is more accurate than other known methods.

A narrowband mixture of noise signal and impulse noise is detected by a linear envelope detector 1. The probability density distribution of the voltage U (t) at the output of the linear detector 1 in the detection of normal noise is Rayleigh.

The average number of intersections no (i / o) per unit time of a certain defined level L / o by the voltage U (t) is determined by the expression:

f / g

Uy

n, (U,)

 p - exp

5 V 9-,

 h

where p is a coefficient depending on receiver parameters;

a is the average normal noise power at the detector input;

o (o) - has a single maximum at.

Using this circumstance, the measurement of noise reduces to finding such a level of voltage, Wo. where the number of intersections by the noise signal of this level is maximum.

The voltage from the envelope detector enters the limiter 2 with the following threshold, which monitors the average value of the mixture envelope voltage and, thus, eliminates the possibility of tuning the device to a second maximum, which is caused by impulse noise. Next, the voltage goes to a two-sided limiter 3, which passes a relatively narrow strip of instantaneous values of the input voltage, ranging from UQ to t / o-f At /, to the pulse counter 6. The value of UQ is controlled by potentiometer 9.

From the output of limiter 3, a sequence of nearly rectangular pulses, the number of which is equal to the number of intersections of the envelope level UQ, goes to pulse counter 6, where these pulses are normalized in duration and amplitude and detected to restore the constant component proportional to nu (U (,)).

To generate an error signal controlling the level of the limitation of the two-sided limiter 3, the latter is modulated from the alternator 8 (alternating voltage source e) with the FM frequency. In this case, the pulse occurrence frequency at the output of the limiter 3 is also modulated by this frequency.

The DC voltage from the output of the counter b is filtered and amplified by the filter amplifier 7 tuned to the FM frequency to the value required for controlling the electric motor 5 and fed to one of its windings, the other winding is powered by an alternator 8 of alternating current (source alternating voltage).

The magnitude of the control voltage will be proportional to the modulus of the slope rto (t / o) and will tend to the minimum as it goes. The control voltage phase will change by 180 ° when f / o passes through the level

t / o.

In the case of a steady state of the system t / o, the voltage from the peptimeter 9 is fed to the recording unit 4. To bring the system out of state

when the input signal is necessary to have an initial level. In the proposed device, this level is determined by the level of the noise signal at the input and is accomplished by applying a voltage from the output

limiter with the following threshold 2 through a 10 low pass filter per potentiometer 9.

Subject invention

A device for measuring the intensity of a noise signal and a background of impulse noise based on the principle of finding the voltage level at which the number of intersections of the envelope of a mixture of the noise signal and impulse noise of this level is maximum, containing an envelope detector connected to the signal input of a two-way limiter connected to the recording unit,

and an electric motor, one winding of which through a pulse counter and amplifier filter is connected to another output of a double-sided limiter, another winding to an alternator connected to a control input of a double-sided limiter, and the motor shaft is mechanically connected to a double-sided potentiometer, characterized by that in order to broaden the dynamic range and eliminate

possibility of false tuning, between the envelope detector and the signal input of the two-way limiter, a limiter with the following threshold is turned on, the output of which is also connected via a low-pass filter

to the additional control input of the two-way limiter.

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