SU1167740A1 - Device for protection against interference - Google Patents

Abstract

A PSYCH PROTECTION DEVICE, containing a wide-width connected filter in series, whose input is the device's input, an amplifier, a limiter and a narrow-band filter, an odd-harmonic filter connected in series, an amplifier with a cut-off Minimum and a recorder that has that, in order to increase noise immunity, a threshold pulse shaper with an adjustable threshold level was introduced into it, the input and output were connected respectively with the output of the narrow-band filter and the input of the filter odd th harmonic.

Description

The invention relates to radio engineering and can be used to receive information using high-frequency signals manipulated in amplitude or frequency against a background of impulse noise with random amplitude and duration.

The purpose of the invention is to increase the noise immunity,

The drawing shows a structural electrical circuit of the proposed device to protect against interference

The anti-interference device contains a wideband filter 1, amplifier 2, limiter 3, narrowband filter 4, threshold shaper 5 pulses with adjustable threshold level, odd harmonic filter 6, amplifier 7 with minimum cut-off, recorder 8.

The threshold pulse shaper 5 with an adjustable threshold level contains an operational amplifier 9 with a resistor 10, a bridge 11 formed by diodes 12-15, a voltage regulator source 16 with variable resistors 17 and 18.

The anti-interference device operates as follows.

In the case of receiving high-frequency signals manipulated in amplitude against the background of additive interference (both fluctuating and pulsed), the sum of the manipulated signal and interference from the communication channel passes through broadband filter 1, is amplified by amplifier 2 and fed to the input of limiter 3. If you select the minimum the incoming signal level is 3 dB more than the average noise level at the output of wideband filter 1, then in limiter 3 the signal is suppressed. If the level of intense interference (both fluctuation and pulse), missed by broadband filter 1, exceeds the signal level by more than 3 dB, then in limiter 3 the signal is suppressed by interference. In this case, the output of the limiter 3 is either a signal with a power PJ .. or a disturbance with power P, and

 a 0.81 a

p P with

where a is the limiter limit level 3.

Further transmission of signals and interference in the device is considered separately.

If we neglect the attenuation of narrow-band filter 4 at the signal frequency, then at the filter output we have

P ,, P „0.81 a

effective value of signal voltage

 0.9 a

and.

C4 man

And the amplitude value of this voltage

 1.27a.

silt

 shah

Intense fluctuation interference, suppressing the signal in limiter 3, under the same conditions, has the output of narrowband filter 4

i,

I4

0.81 a

 1, & ii and the effective value of the interference voltage, regardless of its value, is early

6, JJ

uin

0.9 a,

  , but ,

where bf is the bandwidth (at the level of 0.707 x U) of the narrowband filter 4;

bf, - bandwidth of broadband filter 1

Intense impulse noise, suppressing the signal in limiter 3, in the case when the interval between pulses at the output of wideband filter 1 is less than the duration of the pulses themselves, regardless of the amplitude of these pulses in the communication channel (not shown), has an effective voltage value at the output of the narrowband filter four

 c

S ,.

0.9 a

I2ui,

Signal with ampshield U. „1.27a, or interference with the current

the value of 0.9a-4th f / f is fed to the threshold driver 5, which is, for example, the operational amplifier 9, in the circuit

the negative feedback of which is connected to a diode bridge 11. To the other diagonal of this bridge, an alternating current voltage En is applied through the variable resistors 17 and 18 of the value of R. Under stress

any polarity at the input of the op amp 9 and iUgxJ all diodes 12-15 are open and the output voltage

Claims (1)

INTERFERENCE PROTECTION DEVICE containing a broadband filter connected in series, the input of which is the input of the device, an amplifier, a limiter and a narrow-band filter, an odd-harmonic filter connected in series, an amplifier with a minimum cut-off and a recorder, which is connected with it, that, in order to increase noise immunity, a threshold pulse shaper with an adjustable threshold level is introduced into it, the input and output of which are connected respectively to the output of the narrow-band filter and the input of the odd harmonic filter nicks. 1 167740 '1