RU2204202C2 - Device for suppressing broadband phase-keyed noise - Google Patents

Abstract

FIELD: radio engineering; broadband-signal communication systems. SUBSTANCE: device has series-connected first delay element, multiplier, and rejection filter, second rejection filter, and second multiplier; series-connected low-frequency filter whose input is connected to output of first multiplier, amplitude detector, and threshold comparison unit; series-connected third delay element and amplifier; series-connected limiter, band filter whose output is connected to reference input of first multiplier, and second delay element whose output is connected to reference input of second multiplier; it also has switch whose first and second signal inputs are connected respectively to amplifier output and to second multiplier output, third control input, to output of threshold comparison unit; inputs of first and third delay elements as well as limiter output function as device input. EFFECT: enhanced degree of high-power noise suppression. 3 dwg

Description

 The device relates to radio engineering and can be used in communication systems with broadband signals.

 Known interference suppression devices described in the monograph "Theory of signal detection", ed. P.A. Bakuta. - M .: Radio and communications, 1984, pp. 294-297, 322-325, as well as in the journal "Radio Engineering", 8, 1984, pp. 33-35, the disadvantage of which is the low degree of suppression of broadband phase-shifted interference.

The closest in technical essence to the proposed is the device described in the article V.P. Efimova "Assessment of the effect of nonlinear conversion on the noise immunity of reception in satellite networks, published in the journal" Electromagnetic Systems ", 1, v.3, 1998, p. 95, adopted as a prototype, the structural diagram of which is shown in figure 1, where indicated :
1 - amplifier;
2 - subtractor;
3 - limiter;
4 - band-pass filter.

 The prototype device contains a series-connected limiter 3, a band-pass filter 4 and a subtractor 2, the output of which is the output of the device, and the input of the limiter 3, which is the input of the device, is connected through an amplifier 1 to the second input of the subtractor 2.

 The prototype device operates as follows.

The input mixture, which contains a powerful noise with amplitude and a weak useful signal, enters through the block 1, where it is amplified, to the second input of block 2, and through the series-connected blocks 3 and 4 to the first input of block 2. In blocks 3 and 4, suppression powerful interference of a weak signal due to the limitation of the input mixture in block 3 and filtering the result of the restriction in block 4, this ensures the constancy of the amplitude of the interference estimate, equal to U _about , at any value of the amplitude of the noise at the input of the device.

In block 2, the interference estimate with the amplitude U _о is subtracted from the input mixture, the useful signal and the uncompensated noise balance ΔU _{n are} extracted at the output of block 2.

 The disadvantage of the prototype is the low degree of suppression of broadband phase-shift interference.

 To eliminate this drawback, a commutator, a second and third delay elements, a first delay element, a first multiplier, a first and a second notch are introduced filters and a second multiplier, the output of which is connected to the second signal input of the switch, the output of which is the output of the device.

 A low-pass filter, an amplitude detector, and a threshold comparison unit, the output of which is connected to the third control input of the switch, are introduced in series. The inputs of the limiter, the first delay element and the third delay element are interconnected and are the input of the device, and the output of the third delay element through the amplifier is connected to the first signal input of the switch. In addition, the input of the low-pass filter is connected to the output of the first multiplier, the reference input of which is connected to the output of the bandpass filter and through the second delay element with the second reference input of the second multiplier.

The structural diagram of the inventive device is presented in figure 2, where it is indicated:
1 - limiter;
2 - band-pass filter;
3 - low pass filter;
4 - amplitude detector;
5, 11 and 12 - the first, second and third delay elements;
6 and 8 - the first and second multipliers;
7 and 14 - the first and second notch filters;
9 - switch;
10 - block comparison with the threshold;
13 - amplifier.

 The proposed device has the following functional relationships: series-connected the first delay element 5, the first multiplier 6, the first notch filter 7, the second notch filter 14 and the second multiplier 8, the output of which is connected to the second signal input of the switch 9; the output of the first multiplier 6 is connected to a low-pass filter 3 connected in series, an amplitude detector 4 and a comparison unit with a threshold 10, the output of which is connected to the third control input of the switch 9, the output of which is the output of the device; the input of the first delay element 5 is connected to the third delay element 12 and the amplifier 13 connected in series, the output of which is connected to the first signal input of the switch 9; the input of the limiter 1 is connected to the input of the device, and the output through the bandpass filter 2 is connected to the second reference input of the first multiplier 6 and to the input of the second delay element 11.

 The inventive device operates as follows.

 The input mixture containing a powerful broadband phase-manipulated noise with an a priori known carrier frequency (structural, imitation or relayed), hereinafter referred to as broadband interference, and a weak useful signal, is fed to the first signal input of block 9 through series-connected blocks 12 and 13, and to the second its input is through series-connected blocks 5, 6, 7, 14, 8.

 In block 6, the input mixture arriving at its signal input from the device input is multiplied through block 5 with an estimate of the powerful broadband phase-shift interference (hereinafter referred to as “broadband interference estimation”) synchronous with the noise in the input mixture arriving at the reference input of the block 6 s the output of block 2. As a result of multiplication, the output of block 6 is the convolution of broadband interference into a narrowband interference at the difference and total frequencies. The convolution at the difference (zero) frequency is rejected by block 7, and at the total (doubled) frequency by block 14, which eliminates the passage of broadband interference to the second signal input of block 9.

 At the same time, the useful signal in block 6 is superimposed by the manipulation of the estimate of broadband interference, which is then removed from it in block 8 by multiplying it with the same estimate of the broadband interference coming to the reference input of block 8 from the output of block 2 through block 11.

 The delay values of blocks 5 and 11 are selected in the process of setting up the device so as to ensure the synchronism of the multiplied voltages in blocks 6 and 8, taking into account the hardware delays.

 Thus, broadband interference does not pass to the second signal input of block 9, and the useful signal passes almost without distortion.

 Indeed, in blocks 7 and 14 of the extended spectrum of the useful signal, the narrow parts of its spectrum, which are determined by the notch bands, are edited.

 In block 6, the broadband interference and its estimate correlated with it are multiplied, which differs from the interference in the input mixture only in the initial phase. In this regard, the notch bands of blocks 7 and 14 are extremely narrow, therefore, their influence on the useful signal can be neglected.

 The evaluation (copy) of broadband interference is generated by strictly restricting the input mixture in block 1, followed by filtering the result of the restriction in block 2, the passband of which is equal to the spectral width of the broadband interference. At the output of block 2, a weak useful signal is suppressed by a powerful broadband noise, while in block 1, the level of broadband noise is normalized, which ensures a constant transmission coefficient of the signal when passing through blocks 6, 7, 14, 8 with changes in the level of broadband interference.

 From the output of block 6, the result of convolution of the broadband interference with its estimate is sent to block 3, where it is filtered in a narrow band equal to the spectrum band of the minimized interference at the difference frequency, after which it goes to block 4, where its envelope is extracted due to amplitude detection, which is fed to block 10, where it is compared with a threshold. The command about exceeding (not exceeding) the threshold from the output of block 10 is sent to the third control input of block 9. If the threshold is exceeded, block 10 generates a command "1", upon receipt of which block 9 connects its second signal input (block 8 output) to its output, at the same time, a powerful broadband interference in blocks 6, 7, 14, 8 is edited from the input mixture.

 When the “0” command is generated in block 10, which corresponds to the absence of exceeding the threshold and, therefore, the case of the detection of powerful broadband interference, block 9 connects its first signal input to the output, while the input mixture enters the output of block 9 through series-connected blocks 12, 13 , 9.

 The transmission coefficient of block 13 is chosen equal to the transmission coefficient of the useful signal in the path, consisting of blocks 5, 6, 7, 14, 8 connected in series, and the delay value of block 12 is chosen equal to the delay in these blocks. Such a choice of parameters ensures that the receiver operating mode remains unchanged when the inventive device is installed at its input both in the presence of powerful broadband interference in the input mixture and in its absence.

 The delay value of blocks 5 and 11 is selected during the setup process so that the synchronized multiplied voltages in blocks 6 and 8 are ensured, taking into account hardware delays.

The block diagram of block 9 is shown in figure 3, where indicated:
91, 92 - the first and second key;
93 - inverter.

 Block 9 contains the first key 91, the signal input of which is the first signal input of block 9, the second key 92, the signal input of which is the second signal input of block 9, and an inverter 93, while the third control input of block 9 is connected to the control input of block 91 through block 93, and the control input of block 92 is connected directly to the combined outputs of blocks 91 and 92 and is the output of block 9.

 Block 9 operates as follows.

 When the command “1” appears on the third control input of block 9, it is sent to block 92, unlocking it and providing a signal from block 8 to the output of block 9. At the same time, this command, inverting in block 92, locks block 91. When it appears on the control input block 9 of the command "0" is locking block 92, at the same time, this command is inverted to the command "1" in block 93, which is fed to the control input of block 91, unlocking it. Thus, in this case, the output of block 13 is connected to the output of block 9.

 In the prototype device, the interference estimate has a constant amplitude level equal to the limiter limit level.

With an increase in the level of powerful interference at the input of the prototype device relative to the level U _о , an uncompensated voltage Δ U _n increases, while the degree of suppression of interference decreases sharply.

In the inventive device, a powerful wideband phase-shifted interference is rejected, while the interference assessment, which, as in the prototype, has a constant amplitude level U _о , is not used to compensate for interference, as is the case in the prototype, but as a reference signal during its rejection.

 With an increase in the level of powerful broadband phase-manipulated noise in the input mixture, the voltage amplitude at the reference inputs of blocks 6 and 8 remains constant, while the degree of suppression of interference not only does not decrease (as is the case in the prototype), but even increases, since with an increase in the level of interference by increasing the degree of suppression of the useful signal in block 1, the proportion of the useful signal in the reference signal is reduced.

 Thus, in the inventive device with an increase in the level of broadband phase-shifted interference, the degree of its suppression does not decrease as in the prototype, but increases.

Claims (1)

 A device for suppressing broadband phase-shifted interference, comprising an amplifier and a series-connected limiter, the input of which is the input of the device, and a band-pass filter, characterized in that a switch, a second and third delay elements, a first delay element, a first multiplier, a first and second rejection filters are connected in series and the second multiplier, the output of which is connected to the second signal input of the switch, the output of which is the output of the device, is introduced in series connected by a low-pass filter, an amplitude detector and a threshold comparison unit, the output of which is connected to the third control input of the switch, while the inputs of the limiter, the first delay element and the third delay element are connected to each other and are the input of the device, and the output of the third delay element through the amplifier is connected with the first signal input of the switch, in addition, the input of the low-pass filter is connected to the output of the first multiplier, the reference input of which is connected to the output of the bandpass filter and through the second th delay element - with the second reference input of the second multiplier.

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