RU2388144C1 - Device for suppressing narrow-band interference - Google Patents

Abstract

FIELD: physics, radio. ^ SUBSTANCE: invention relates to radio engineering and can be used mainly in duplex control radio channels and in packet radio networks for operational-command communication in position areas under influence of narrowband interference. The device includes in each of n lines of the unit for protection from narrowband interference, a corresponding electronic switch (101-10n), as well as a first (11) and a second (12) time selector whose outputs are connected to corresponding inputs of an OR circuit (13). The first input of each electronic switch (101-10n) is connected to the output of the corresponding element for suppressing narrowband interference (61-6n), and the output is the corresponding output of the unit for protection from narrowband interference (2). Outputs of the first (11) and second (12) time selectors are connected to the second output of a matched filter (4). The output of the OR circuit (13) is connected to the second inputs of the first (101) and second (102), as well as the last two (10n-1 and 10n) electronic switches. The output of the second time selector (12) is connected to second inputs of the third (103) and (n-2)-th (10n-2) electronic switches. ^ EFFECT: increased efficiency of using the allocated frequency band, which enables increase of the signal-to-noise ratio. ^ 2 dwg

Description

The invention relates to the field of radio engineering and can be used mainly in duplex radio channels of control and packet radio networks of operational-command communication in position areas under the influence of narrow-band interference.

A device for suppressing narrowband interference in AS No. 754681, Н04В 1/10, USSR, containing n self-tuning notch filters connected in series, however this device, together with the interference, suppresses part of the spectrum of the useful signal.

A device is known by A.S. No. 720730, Н04В 1/10, in which a comb of switched filters is used to suppress noise. The disadvantage of this device is its complexity due to the presence of a comb of narrow-band switched filters and additional electrical losses caused by the non-identity and time instability of the amplitude and phase characteristics of individual filters.

Closest to the technical nature of the proposed device is a noise suppression device, presented in the book "Interference immunity of radio systems with complex signals", ed. G.I. Tuzova, M., "Radio and Communications", 1985, p. 211, Fig. 7. 3a adopted as a prototype.

Figure 1 shows the functional diagram of the device of the prototype, where indicated:

1 - broadband amplifier of intermediate frequency (UPCH);

2 - narrowband jammer (protection unit);

3 - adder;

4 - matched filter;

5 ₁ -5 _n - narrow-band amplifiers of intermediate frequency (UPCH);

6 ₁ -6 _n - elements for suppressing narrowband interference;

7 - multiplier;

8 - integrator;

9 - reference signal generator.

The prototype device contains a serially connected broadband amplifier 1 and a protection unit 2, n outputs of which are connected to the corresponding inputs of the adder 3, the output of which is connected to the input of the matched filter 4, the output of which is the output of the device. In this case, the protection unit 2 contains n parallel channels, each of which consists of corresponding series-connected narrow-band amplifier 5 and the elements of suppression of narrow-band interference 6, the outputs of which are the corresponding outputs of the protection unit 2. The inputs of the narrow-band amplifier 5 ₁ -5 _{n are} combined and are the input of the unit protection 2. The input of the broadband amplifier UPCH 1 is the input of the device. The matched filter 4 contains a series-connected multiplier 7 and an integrator 8, the output of which is the output of the matched filter 4, as well as a reference signal generator 9, the output of which is connected to the first input of the multiplier 7, the second input of which is the input of the matched filter 4.

The prototype device works as follows.

After the frequency conversion, the received broadband signal (SHPS) is fed to the input of the broadband IF 1, where it is amplified to the required value and then fed to the narrow-band interference suppressor (protection unit) 2, using narrow-band IF filters 5 ₁ -5 _{n, the} entire frequency band of the SHPS is divided into n partial channels:

,

,

where Δf is the partial channel bandwidth;

ΔF is the bandwidth of the received ShPS;

n is the number of partial channels.

Moreover, the bandwidth of all n partial channels should be the same and, in addition, the frequency bands of the partial channels should not overlap. Therefore, the amplitude-frequency characteristic (AFC) and phase-frequency characteristic (PFC) of an interference suppressor (protection unit) 2 is represented as the sum of the AFC and PFC of individual channels.

In each frequency channel, in addition to the narrow-band filter, there is an amplifier with which the attenuation in the filter of its partial channel is compensated.

The bandwidth of each partial channel is selected so that no more than one narrow-band interference gets into each partial channel.

If there is narrowband interference in any of the partial channels, it is suppressed in the corresponding suppression element 6. The narrowband interference suppression elements 6 ₁ -6 _n , which are non-linear elements, operate either in the input mixture limiting mode or in the key mode (the channel is open at low levels of interference and closed at high levels of interference).

From the output of the interference suppressor (protection unit) 2, the signal at n outputs is fed to the adder 3, where it is summed over the frequency band ΔF = n · Δf.

From the output of the adder 3, the ШПС is fed to the input of a matched filter 4, which can be used as a passive matched filter based on a multi-tap delay line, or as an active matched filter - correlator. Using the matched filter 4 merges the broadband modulation, i.e. folding.

.The minimum duration of an element of a pseudo-random sequence (PSP) is equal to τ and a frequency band is allocated under it, determined from the relation

.

But parcels of duration τ ₀ occupy only 20–25% of the SRP cycle, and the majority of the time is occupied by blocks of parcels 2τ ₀ , 3τ ₀ ... nτ ₀ , where n is the degree of generation of the polynomial equal to the capacity of the generating SRP registers. Naturally, for these blocks of parcels a frequency band is required much less than ΔF, namely for blocks of parcels 2τ ₀ , 3τ ₀ ... nτ ₀ a frequency band is already required, i.e. for 2τ ₀ twice, for 3τ ₀ three times, etc. than for τ ₀ , then for 2τ ₀ only half of the channels of protection block 2 will be filled with a useful signal, and in the other half there will be only noise, which leads to total increase in noise of the total signal.

The disadvantage of this prototype device is the inefficient use of the allocated frequency band, which leads to a deterioration in the signal-to-noise ratio.

To eliminate this drawback, a device containing a series-connected wideband intermediate-frequency amplifier (IFA) and a narrow-band interference protection unit, n outputs of which are connected to the corresponding inputs of the adder, the output of which is connected to the first input of the matched filter, the first output of which is the output of the device, this protection unit contains n parallel rulers, each of which consists of a corresponding series-connected narrow-band amplifier and a narrow-band suppression element interference, and the inputs of n narrow-band amplifier are combined and are the input of the protection unit, the matched filter consists of series-connected multiplier and integrator, the output of which is the first output of the matched filter, and the first input of the multiplier is its input, in addition, the output of the reference signal generator is connected to the second input of the multiplier, the input of the broadband amplifier is the input of the device according to the invention, a corresponding electronic key is inserted into each of the n lines, the first input of each of which is connected nen with the output of the corresponding narrowband interference suppression element, and the output is the corresponding output of the narrowband interference protection unit, in addition, the inputs of the first and second time selectors are connected to the second output of the matched filter, which is the output of the reference signal generator, the outputs of the first and second time selectors are connected to the corresponding inputs of the OR circuit, the output of which is connected to the second inputs of the first, second, n-1 and n-th electronic keys, and the output of the second temporary selector is connected inen with the second inputs of the third, and n-2 electronic keys.

Figure 2 shows the functional diagram of the proposed device, where indicated:

1 - broadband amplifier of intermediate frequency (UPCH);

2 - protection unit against narrow-band interference (suppressor of narrow-band interference);

3 - adder;

4 - matched filter;

5 ₁ -5 _n - narrow-band amplifiers of intermediate frequency (UPCH);

6 ₁ -6 _n - elements for suppressing narrowband interference;

7 - multiplier;

8 - integrator;

9 - reference signal generator;

10 ₁ -10 _n - electronic keys;

11, 12 - the first and second temporary selectors;

13 is an OR diagram.

The proposed device contains a broadband amplifier 1, the output of which is connected to the input of the suppressor of narrowband interference 2, n outputs of which are connected to the corresponding n inputs of the adder 3, the output of which is connected to the input of the matched filter 4, the first output of which is the output of the device. In this case, the narrow-band interference suppressor consists of n parallel channels, each of which contains the corresponding narrow-connected narrow-band amplifier 5, the narrow-band interference suppression element 6 and the electronic key 10, and the output of each of the n electronic keys 10 is the corresponding output of the narrow-band interference suppressor 2, and the inputs n narrow-band amplifiers 5 ₁ -5 _{n are} combined and are the input of the suppressor of narrow-band interference 2.

The matched filter 4 contains a series-connected multiplier 7 and an integrator 8, the output of which is the first output of the matched filter 4, as well as a reference signal generator 9, the output of which is connected to the second input of the multiplier 7, the first input of which is the input of the matched filter 4. In addition, the output the generator of the reference signal 9 is the second output of the matched filter 4 and is connected to the inputs of the first 11 and second 12 time selectors, the outputs of which are connected to the corresponding inputs of the circuit OR 13, you od which is connected to the control input 10 of the first _1, second 10 ₂ penultimate 10 _n-1 and 10 _n of the last electronic key. The output of the second temporary selector 12 is connected to the controlled inputs of the third 10 ₃ and (n-2) th 10 _n-2 electronic keys.

The proposed device operates as follows.

The adopted SHPS after frequency conversion is fed to broadband IF 1, where it is amplified to the required value and then fed to the narrow-band interference suppressor 2. Using narrow-band IF filters 5 ₁ -5 _{n, the} entire frequency band is divided into n partial channels

,

,

where Δf is the partial channel bandwidth;

ΔF is the bandwidth of the received ShPS;

n is the number of partial channels.

Moreover, the bandwidth of all n partial channels should be the same and, in addition, the frequency bands of the partial channels should not overlap. Therefore, the amplitude-frequency characteristic (AFC) and phase-frequency characteristic (PFC) of an interference suppressor (protection unit) 2 is represented as the sum of the AFC and PFC of individual channels.

In each frequency channel, in addition to the narrow-band filter, there is an amplifier with which the attenuation in the filter of its partial channel is compensated.

The bandwidth of each partial channel is selected so that no more than one narrow-band interference gets into each partial channel.

If there is narrowband interference in any of the partial channels, it is suppressed in the corresponding suppression element 6. The narrowband interference suppression elements 6 ₁ -6 _n , which are non-linear elements, operate either in the input mixture limiting mode or in the key mode (the channel is open at low levels of interference and closed at high levels of interference).

From the output of the interference suppressor (protection unit) 2, the signal at n outputs is fed to the inputs of the corresponding electronic keys 10 ₁ -10 _n .

Since the minimum duration of the element of the SRP supplied to the input of the device is τ ₀ and a frequency band is allocated under it

,

,

such parcels of duration τ ₀ occupy about 20–25% in the PSP cycle, and the majority of the time is occupied by blocks from packages 2τ ₀ , 3τ ₀ ... nτ ₀ , then τ ₀ when all the channels (lines) of the protection block arrive at the input of the PSP element τ ₀ will be filled with a useful signal. But when entering the input of the device of the PSP unit, consisting of 2τ ₀ , only half of the lines of the protection unit 2 will be filled with a useful signal, and the remaining half of the lines of the protection unit 2 will contain only noise, and when entering the input of the device of the PSP unit of 3τ ₀ , only one third of the rulers will be filled with a useful signal, etc. In such cases, so that the noise from the lines not filled with the useful signal does not enter the total signal, they must be closed using electronic keys 10 ₁ -10 _n . So when it arrives at the input of the device of the PSP unit with a duration of 2τ ₀ , at the same time, from the signal of the reference oscillator 9, the block 2τ ₀ is selected by the first temporary selector 11 and, through the OR 13 circuit, is supplied to the controlled inputs of the first 10 ₁ , second 10 ₂ , last but one 10 _n-1 and last 10 _n electronic keys, closing them. When a block of 3τ ₀ duration is received by the second temporary selector 12 from the reference signal generator 9, a block of 3τ ₀ duration is selected and, through the OR 13 circuit, is supplied to the controlled inputs of the first, second, n-1 and nth electronic keys, closing them for 3τ ₀ , and from the output of the second temporary selector 12, it is fed to the controlled inputs of the electronic keys 10 ₃ , 10 _n-2 , closing them for a time equal to 3τ ₀ .

Thus, the proposed device allows you to effectively use the allocated frequency band, which leads to an increase in the signal-to-noise ratio by at least two times.

Claims (1)

A narrow-band interference suppression device, comprising a series-connected intermediate-frequency amplifier (IFA) and a narrow-band interference protection unit, n outputs of which are connected to the corresponding inputs of the adder, the output of which is connected to the input of a matched filter, the first output of which is the output of the device, while the protection unit contains n parallel rulers, each of which consists of a corresponding series-connected narrow-band amplifier and an element for suppressing narrow-band interference, m the inputs of n narrow-band amplifier are combined and are the input of the protection unit, the matched filter consists of series-connected multiplier and integrator, the output of which is the first output of the matched filter, and the first input of the multiplier is its input, in addition, the output of the reference signal generator is connected to the second input of the multiplier , the input of the broadband amplifier is the input of the device, characterized in that the corresponding electronic key is inserted into each of the n lines, the first input of each of which is connected to the output of the corresponding narrowband interference suppression element, and the output of each key is the corresponding output of the narrowband interference protection unit, in addition, the inputs of the first and second time selectors are connected to the second output of the matched filter, which is the output of the reference signal generator, and the first time selector allocates memory blocks of 2τ duration _0, a second timing selector - length 3τ _0, outputs of the first and second time gates through an OR gate connected to the control inputs of said first, vtorog , N-1 and n-th electronic switches, in addition, a second timing selector output coupled to control inputs of the third and the n-2 electronic keys.

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