SU1084995A1 - Device for protecting against noise - Google Patents

Abstract

A INTERFERENCE PROTECTION DEVICE, containing a recorder and a wideband filter connected in series, an amplifier, a limiter and a narrowband filter, characterized in that, in order to increase the noise immunity with respect to impulse noise with random amplitude and duration, between the output of the narrowband filter and the recorder input are connected in series additional limiter, filter for odd harmonics and amplifier with minimum cutoff.

Description

00

4; ii. This 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. A protection device is known that contains a broadband filter connected in series, a limiter and a narrowband filter. However, the device must have a sufficiently narrowband filter to provide the required noise immunity, which leads to a delay in the input useful signal. The closest to the invention in technical terms is an anti-interference device containing a recorder and a coupled-in-consequence broadband filter amplifier, limiter and narrowband filter G2. However, the known device has insufficient noise immunity when exposed to pulsed noise with a random amplitude and duration, subject to the speed conditions, i.e. bandwidth of the .band filter. The purpose of the invention is to increase the immunity to impulse noise with a random amplitude and duration. This goal is achieved by the fact that in a noise protection device containing a recorder and a wideband filter connected in series, an amplifier, a limiter and a narrowband filter, an odd harmonic filter and a minimum cutoff amplifier are connected between the narrowband filter output and the recorder input. The drawing shows the structures on the electrical circuit of the proposed device. The anti-jamming device contains a wideband filter 1, amplifier 2, limiter 3, narrowband filter 4, additional limiter 5, odd harmonic filter b, amplifier 7 with minimum cutoff and recorder 8. The device works as follows. Consider the operation of the device with high-frequency signals manipulated in amplitude against the background of additive interference (both fluctuation and pulse). The sum of the manipulated signal and interference from the communication channel passes through (input ™) broadband filter 1, is amplified by amplifier 2 and fed to limiter 3 input. If you select a minimum incoming signal level 3 dB more than the average noise level at the output of wideband filter 1, then a 3 signal noise suppression will occur in the limiter 3. If the level is intense fur (both fluctuation and impulse) missed by broadband filter 1 exceeds the signal level by more than 3 dB, then suppressor 3 will suppress the signal by interference. In all cases, it can be considered that there is either a signal at output 3 power or interference power P, j, j, and J T Rsz where a is the limiter level of the limiter 3. Considering the above, further transmission of signals and interference in the receiver is considered separately. If we neglect the attenuation of the narrow-band filter 4 at the signal frequency, then at the output of this filter we have the RSZH RSZ 081a valid voltage value. Signal US 09 ", and the amplitude value of this voltage is 1.27a. MF max. S Intense fluctuation interference, suppressing the signal in the limiter 3, under the same conditions, has at the output of the high-pass filter 4 a power 4 at the R ... RP. and the effective value of the interference voltage, regardless of its magnitude in the communication channel, is where. E {- is the bandwidth {at the level of 0.707 e-bandpass filter 4; - bandwidth of broadband filter 1, Intense impulse, suppressing the signal in limiter 3, in the worst case, when the interval between 1111pulses at the output of broadband filter 1 is less than the duration of the pulses, has, regardless of the amplitude of these pulses, regardless of amplitude of these these pulses in the channel

connection the effective value of the voltage at the output of the narrowband filter 4

Yi.p, 9s, 6 ,.

If at the level of restriction of the additional limiter 5 E () set up the filter b

I am i.ji

for transmitting the k-th harmonic of the carrier frequency of the signal, then, decomposing a sinusoid bounded on both sides in the rd Fourier, we get the signal of the k-th odd harmonic at the filter output 6

4E

U (iccosoCsin -SinoLcoskoC)

 Jr (lc2-1) 1

  ji If

Sin1cuJt | U | sin4wt

EI

where (i-c (rc3iri

carrier frequency

cm msn signal; LO is the angle at which a sinusoidal signal begins to be limited in the additional limiter 5.

If the threshold is a minimum cut

amplifier 7 make equal

-175that if there is a signal at the device input, which corresponds to a logical unit, it continuously enters the registrar 8, and after j time at the output of reg 8, a Log, 1 signal (jump of the output voltage, actuation of the output relay, etc.) d.) From

the presence of a signal at the input of the device corresponds to the log. About at the output of the recorder 8.

Since the interference with a random amplitude smaller than E has a frequency approximately equal to the average tuning frequency of the UEband filter 4 and the wideband filter 1 - .ucp /, it passes through an additional limiter 5 without distortion and does not

O is passed by the filter b. Therefore, a false signal under the influence of interference can occur at the output of recorder 8, if the random amplitude of interference at the output of narrowband filter 4 exceeds the value of E. During this time, it should be noted that at 0 75 ° and E-, const, the decrease in emission amplitude interference up to 0 98ERC | d and an increase in the ejection amplitude to 1.03 Ej.y. leads to the fact that the amplitudes of the harmonics of the interference, starting from the third, are reduced compared with the amplitudes of the same harmonics of the signal

5 is more than 1.5 times, and the interference is not transmitted by the amplifier 7 with a minimum cutoff.

The bandwidth of the filter 6 is determined only by the detuning from the adjacent harmonics of the signal, and by choosing the appropriate harmonic number of the limited sinusoidal signal, it can be made arbitrarily large.

5 Thus, the proposed device allows, with the same signal delay as that of the known, to increase its noise immunity or, with the same noise immunity, to improve the speed, 0

Claims (1)

AN INTERFERENCE PROTECTION DEVICE, comprising a recorder and a broadband filter, amplifier, limiter and narrow-band filter connected in series, characterized in that, in order to increase the noise immunity with respect to pulsed noise with a random amplitude and duration, between the output of the narrow-band filter and the recorder input an odd harmonic filter, an odd harmonic filter and a cut-off amplifier to a minimum. ">