SU1589401A1 - Interference suppression device - Google Patents

Abstract

The invention relates to radio engineering and can be used to extract a weak pulse signal from its additive mixture with much stronger than a useful signal by the receiver. The purpose of the invention is to increase the ratio of the power of the useful pulse signal to the power of the pulse interference at the output of the device, provided that the duration of the useful signal is shorter than the duration of the pulse interference, and the power of the pulse interference is much greater than the power of the useful signal. The elements 4, 5, filters 13, 17, switches 11, 18, 15, amplitude detector 7, blocks 10, 14, 6, peak detector 8, attenuator 9, as well as the amplitude limiter 1 with a controlled level of restriction provide at the output of a strong signal interference suppression device by subtracting it from a mixture with a weak useful signal. 3 il.

Description

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I The invention relates to radio engineering and can be used for 1 receiving a weak pulse signal from its additive mixture with a receiving device with much more strong interference than a useful signal.

The purpose of the invention is to increase the output power of the useful pulse signal to the power of a pulsed noise at the output of the device under the condition that the duration of the useful signal is shorter than the duration of the impulsive noise and the power of the pulse jr

Noise interference is much greater than the power of the useful signal.

Fig. 1 shows a structural electrical circuit of the interference suppression device; in fig. 2 - plots, 0 ns of spachenes, which clarify the operation of the device; in fig. 3 shows an example of execution of memory blocks.

The noise suppressor contains an amplitude limiter 1, you are 25

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5 lnn with controlled level limiting, subtractor 2, bandwidth 3, first delay element 4, second delay element 5, block 6 c) avneni, amplitude detector 7, PEAK detector 8, attenuator 9, first memory block 10, second translation) 11, the first. amplifier 12, first low pass filter 13, second memory block 14 of memory, third switch 15, second amplifier 16, second low pass filter 17, first switch 18.

: The first and second blocks 10, 14 pam - Tijt contain the key 19, the capacitor 20, the first, second, third and fourth diodes 21-24.

The device works as follows.

At the output of the amplitude detector 7, the envelope of the received radio signal is formed, shown in FIG. 2 line a. At the output of the peak detector 8, a signal is generated, shown in FIG. 2 line b. Using an attenuator 9 that has a factor of less than one, for example, the output level of the pico-boi detector of detector 8 is reduced so that the pulse noise ratio (line g in fig. 2) exceeds the level formed by attenuator 9 (line with fig 2), and the amplitude of the base of the pulses — continuous interference — is not

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exceeds this level. By means of block 6, the level of the output signal of the attenuator 9 is compared with the level of the decoder signal of amplitude detector 7.

If the signal from detector 7 exceeds the level generated by the attenuator 9, the output of block 6 is a constant voltage that falls on the switches 11, 15, 18 and blocks 10, 14. In case the signal from the detector 7 does not exceed the level generated Attenuator 9, at the output of block 6, there is no voltage.

FIG. 2, the time interval from t to tj corresponds to the period of validity and on the receiving device of a large-amplitude impulse noise. At time t, the signal of the amplitude detector 7 exceeds the level of the output signal of the attenuator 9, unit 6 is activated and a constant voltage appears at its output, which is control for switches 11, 15, 18 and blocks 10, 14. Switch 11 at the supply of a control voltage connects the output of the amplitude detector 7 to the input of the amplifier .12. The switch 18 connects the filter output 13 and the control input of the amplitude limiter 1. Thus, the limitation threshold is controlled by a circuit, the amplitude detector 7 - amplifier 12 - filter 13, and the time constant is determined by filter 13 and can be quite large, as determined only by the condition for tracking slow changes in pulse amplitude. A switch 15 connects the output of the unit 14 and the output of the amplifier 16 ,. The almost constant voltage at the output of the unit 14 does not allow the filter capacitor 17 to discharge. This is necessary because the capacitor of the filter 17 can be significantly discharged for a long pulse duration, which, if continuous interference has a large amplitude, leads to loss information due to the inertia determined by the filter 17. In the period of the impulse noise, the block 10 is charged to the level of the impulse. The output signal of block 10 is shown in figure 2 by line d, and block 14 by line e. Block 14 memorizes the signal level during the absence of a pulse.

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The length of time from t to tj in FIG. 2 corresponds to the period between two impulse noise when the device only has a continuous narrowband or wideband interference. At time t, the signal of the amplitude detector 7 becomes lower than the level generated by the attenuator 9, and the voltage at the output of unit 6 is absent. A switch 11 connects the output of block 10 to the input of amplifier 12. Block 10 maintains the voltage across the capacitor of filter 13 approximately constant and close to the level of interference that occurs in the time interval immediately before t This is necessary because with a large time interval between pulses the interference of the filter capacitor 13 can be discharged almost to the level of the interference and during the next pulse the adjustment system, due to the inertia determined by the filter 13, will not be able to correctly track the noise around it. The switch 15 connects the input of the amplitude detector 7 to the input of the amplifier 16. The switch 18 connects the output of the filter 17 to the control input of the amplitude limiter 1. The control circuit of the amplitude detector 7 - amplifier 16 - the filter 17 tracks the base of the noise. The time constant of this circuit is determined by the time constant of the filter 17, which in the general case is not equal to the time constant of the filter 13 and is chosen from the condition of tracking the change in the amplitude of the continuous noise. At the same time, the capacitor of the unit 14 is charged with the voltage supplied from the amplitude detector 7.

Thus, at each moment of time, the control input of the amplitude limiter 1 receives an adjustment signal, according to which the level of the limit changes. By improving the amplitude response, the amplitude limiter 1 cascades and has a selective system at its output. Amplitude limiter 1 removes the useful signal (interference curve f in FIG. 2) from the mixture of the interference and the useful signal so that the output of the subtractor 2 receives a useful signal that is significantly free from interferences. The residual interference at the output of the subtractor 2 suppresses the band-pass filter 3,

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Elements 4 and 5 of the delay are used to take into account the time lag of the signal in the control circuits and in the amplitude limiter 1. One of the possible implementation of blocks 10, 14 is in FIG. When key 19 is open, if the voltage on the capacitor 20 is less than the amplitude of the signal at the input of the block 10.14, the capacitor 20 is charged through the first diode 21, the second diode 22 and the switch 19, and if the amplitude of the signal at the input is less than the voltage on the capacitor 20, the last is discharged to the amplitude of the signal through the third 23, fourth diode 24, and key 19. With the open key 19, the input voltage does not affect the capacitor 20, therefore, with a large capacitor 20, the output voltage is kept approximately constant.

Block 10 differs from block 14 in that the key 19 in one of the blocks is opened by a high and in the other by a low level of control voltage.

Thus, by tracking the level of pulse noise, the level of noise in the intervals between the noise pulses and the corresponding adjustment of the level of limitation of the amplitude limiter 1, the output of the subtractor 2 separates the pulse of the useful signal (Fig. 2).

Claims (1)

Invention Formula An interference suppressor comprising first and second amplifiers connected in series with subtractor-i, the input of which is subtracted is connected to the output of the amplitude limiter, and the Band-pass filter, the output of which is the output of the device, characterized in that in order to increase the power ratio of the useful pulse signal to the power of the pulse noise at the output of the device, provided that the duration of the useful signal is less than the duration of the pulse noise, and the power of the pulse noise is much greater than the power of the first signal, the input of which is the input of the device, and the output is connected to the input of the decrement subtractor, the first phi, 5-sec of each frequency, the input of which is co-ordinated with the ALARM of the first amplifier, the second delay, whose input is connected with the input of the device, and the receiver is connected to the input of the amplitude boom)) akchitel 5, connected by a sequence. ne with  limiter (sequentially, the amplitude de TeiCTOpj input of which is connected to the input of the device, the first memory block and the second switch, another input 1 the second low-pass filter and the out switch, the output of which is connected to the control input with the amplified limiting level, and that input is connected to the output of the first low pass filter connected which is connected to the output of the amplitude detector, and the output is connected to the input of the first amplifier, connected in series to a second memory unit, the input of which is connected to the output of the amplitude detector, and a third switch, the output of which is connected to the input of the second amplifier, and another input to the output of an amplitude detector, a peak detector connected in series, the input of which is connected to the device's input, an attenuator and a comparison unit, another input of which is connected to the output of the amplitude detector, and the output is connected with the control inputs of the switches and the inputs for managing the recording of memory blocks. -.- ooo /  l  / 1589401 f f FIG. 2