Composite phase-keyed signal receiver suppressing narrow-band noise

FIELD: radio engineering; portable composite phase-keyed signal receivers.

SUBSTANCE: proposed receiver has multiplier 4, band filter 6, demodulator 8, weighting coefficient unit 5, adding unit 7, analyzing and control unit 10, synchronizing unit 3, n pseudorandom sequence generators 21 through 2n, decoder 1, and switch unit 9. Receiver also has narrow-band noise suppression unit made in the form of transversal filter. Novelty is that this unit is transferred to correlator reference signal channel, reference signal being stationary periodic signal acting in absence of noise and having unmodulated harmonic components that can be rejected by filters of simpler design than those used for rejecting frequency band of input signal and noise mixture. Group of synchronized pseudorandom sequence generators used instead of delay line does not need in-service tuning.

EFFECT: facilitated realization of narrow-band noise suppression unit; simplified design of rejection filters.

1 cl, 8 dwg

 

The present invention relates to the field of radio and can be used in portable receivers complex phase-shift keyed signals (SFMS).

The most widely known method of suppressing narrowband interference in receivers SFMS is the use of so-called whitening filter based on the comb notch filters [Interference protection radio systems with complex signals. Edited Heatwave. - M.: Radio and communication, 1985, RES. on str]. Typically the whitening filter provides rejection of part of the spectrum SFMS affected escapeplan a hindrance. However, enforcement of non-distortionary combs narrowband filters with mutually agreed characteristics and the large coefficient of suppressing narrowband interference by disabling one of them is connected with considerable difficulties, large size and high cost.

More promising is the suppression of narrowband interference using discrete (digital) programmable transversal filter (PTF).

Functional diagram of the adaptive correlation receiver SPMs, including PTF, [Interference protection radio systems with complex signals. Edited Heatwave. - M.: Radio and communication, 1985, RES. on str] and model correlator [Digital radio receiving system: a Handbook. Edited Mieczyslawa. - is.: Radio and communication, 1990, fig.6.9. lace on str], adopted for the prototype presented in figure 1, where indicated:

I - programmable transversal filter (PTF);

II - correlation receiver.

1 - diagram of the subtraction;

2 - line delay;

3 - the unit of analysis and management;

4 - multiplier;

5 is a pseudo - random sequence generator (SRP);

6 - unit synchronization;

7 is a block weighting coefficients;

8 - bandpass filter;

9 is a block summation;

10 - demodulator.

The device prototype consists of a programmable transversal filter I role block suppression of narrowband interference, the correlation receiver II, scheme subtracting 1 and unit analysis and management 3. The input of the delay line 2 is the input device and combined with the first input of the differential subtracting 1, the output of which is connected to the (n+1)-th entry unit of analysis and control 3 and the signal inputs of the synchronization unit 6 and the multiplier 4, the output of which is connected in series through the band-pass filter 8 and the demodulator 10 is connected to the output device. n outputs of the delay line 2 is connected to the signal n input unit weights 7 and n the unit of analysis and management 3, n outputs of which are connected with the control n input unit weights 7, n outputs of which are connected to the respective n inputs summation block 9, you are the od which is connected with the second input of the differential subtraction 1. The output of the synchronization unit 6 is connected to the input of the clock pulse generator SRP 5, the first and second outputs of which are connected with the respective reference inputs of the synchronization unit 6, while the third generator output SRP 5 is connected to the reference input of the multiplier 4.

The operation of the receiver prototype is as follows. In the scheme of subtracting 1 are compensated input narrowband interference by subtracting from the input mixture signal and interference copies of these interference formed by a transversal filter I. PTF I, consisting of a delay line with 2 taps, block weights 7 and the adder 9, has a pulse transition function corresponding to the amplitude-frequency response, highlighting the range of frequencies affected narrowband interference (creates copies of them). The formation of copies interference produced by appropriate adjustment of the weighting coefficients in the block 7 by commands from the unit of analysis and management 3. The accuracy of formation of the copies of the narrowband interference is determined by the algorithm of functioning of the unit of analysis and management 3. With the output of the circuit subtracting 1 input mixture with depressed narrowband interference received at the input of the correlation receiver II, where the multiplier 4 SFMS removed manipulating the SRP by multiplying the input SFMS with the support of the SRP, verbatim the emnd generator SRP 5. Next, the signal is passed through the filter 8, the band is consistent with the bandwidth information. The signal demodulation is carried out by the unit 10, the output of which is allocated to the signal information. The combination of time manipulating and supporting the SRP is provided by the synchronization unit 6.

In the case of coherent processing of the input mixture flows on videocasette, so the need to use a bandpass filter 8 is eliminated, and the demodulator 10 is reduced to the integrator with reset.

The main drawback of the prototype is its complexity due to:

- the need to ensure a large delay time and a large number of taps in the delay line 2;

- high-capacity digital samples;

- the need to adjust a large number of weight coefficients in the block 7;

- complexity of algorithms, laying the basis for the operation of unit 3, which is usually implemented in the form of microcomputers.

The complexity of the device prototype is due largely to the fact that the delay line PTF is located in the path of the input signal of the correlator. Its analog implementation is very complex ['yashchev LI Design of delay lines. - M.: Owls. Radio, 1972. - 192 pages].

The implementation in digital form requires a large amount of memory, due to the high bit numbers (usually 16-18) and b is a great number of samples of the signal, to be stored.

The objective of the present invention, the reduced complexity implementation of block suppression of narrowband interference, made in the form of fog, and the possibility of its use in portable receivers SFMS. In the proposed device, it is achieved:

- the transfer of the block of suppressing narrowband interference in the path of the reference, not the input signal of the correlator. The reference signal is stationary, periodic, always acting in the absence of noise, resulting in its spectrum consists of the unmodulated harmonic components, registrovat which can significantly simpler filters compared to filters designed for rejectio bandwidth of the input mixture signal and interference;

- use PTF instead of the delay line group synchronized generators SRP, to implement each of which requires approximately log2N trigger (memory cells), where N is the number of elements in the period of the SRP. Usually log2N~10-11, i.e. the required amount of memory is more than an order of magnitude less than in the device-prototype;

- the fact that transversal filters with group generators SRP during operation do not require adjustment. They are equivalent bandpass filters with adjacent amplitude and frequency characteristics. However, they pass (or not pass) no cha is totie strip, and individual harmonics with fixed frequencies. Therefore, their implementation is easier to implement transversal filter device prototype.

To solve the problem in the receiver complex phase-shift keyed signals containing connected in series multiplier, bandpass filter and demodulator, and the block weights, unit totals, the unit of analysis and management, the synchronization unit and the first generator of the SRP, the first and second outputs of which are connected with the respective reference inputs of the synchronization unit, the output of which is connected with a clock generator input SRP, while the signal input to the synchronization unit is combined with the signal input of the multiplier and (k+1)-M input unit of analysis and control, and the output of the decoder is the output of the receiver according to the invention introduced decoder block keys, (n-1) generators of pseudo-random sequence clock inputs of which are connected with the output of the block sync signal input which is the input of the receiver, setting the inputs of all n generators SRP is connected to the output of the decoder, the m inputs of which are connected with the corresponding m outputs of the first pseudo-random sequence generator, and (m+1)th outputs of all n generators SRP connected to respective n inputs unit weight of coefficients is of antov, kn outputs of which are connected with the corresponding kn inputs summation block, the k outputs of which are connected with the signal k inputs of the block of keys that control the k input of which is connected with the corresponding k outputs of the unit of analysis and management, k inputs of which are connected with the corresponding k outputs of the block of keys, (k+1)-th output of which is connected to the reference input of the multiplier.

Graphic materials submitted in the application:

Figure 1 - functional diagram of the device of the prototype.

2 is a functional diagram of the device.

Figure 3 - diagram of the formation of harmonics of the SRP.

Figure 4 - location of the harmonics on the frequency axis.

Figure 5 - example of structure of a transversal filter.

6 is a functional diagram of the generator of the SRP with the decoder.

7 is a functional block circuit analysis and management.

Fig - functional diagram of the block of keys.

Functional diagram of the device is shown in figure 2, where indicated:

I - block delay;

II - transversal filter;

1 - decoder;

21, 22, ... 2n- synchronized generators SRP;

4 - multiplier;

5 - the unit of weight coefficients;

6 - band-pass filter;

7 is a block summation;

8 - demodulator;

9 is a block key;

10 - the unit of analysis and management.

The proposed device contains pic is edutella United multiplier 4, band-pass filter 6 and the demodulator 8, the output of which is the output of the receiver. Signal input of the multiplier 4 is combined with the signal input of the synchronization unit 3, (k+1)-th entry unit of analysis and management 10, and an input device, the Output of the synchronization unit 3 is connected to the clock inputs of all generators SRP 21-2ninstallation inputs are connected to the output of the decoder 1, m inputs of which are connected to respective outputs of the first generator SRP 21and (m-1)-th and m-th outputs of the latter are connected with the respective reference inputs of the synchronization unit 3. (m+1)-e outputs of all generators SRP 21-2nconnected to respective n inputs of unit weights 5, kn outputs of which are connected with the corresponding kn inputs summation block 7, k outputs of which are connected with the signal k inputs of block keys 9, k outputs of which are connected to the corresponding k inputs of the unit of analysis and management 10, k outputs of which are connected with the control k inputs of block keys 9, (k+1)-th output of which is connected to the reference input of the multiplier 4.

On the basis of blocks 21-2n5 and 7 is formed k transversal filters. Therefore, the block 5 has k units of weights (each block has n inputs and n outputs). Hence the total number of outputs in the block 5 is equal to kn. Unit 7 with the holding k adders, each of which has n inputs and one output. Therefore, the block 7 has n inputs and k outputs.

The operation of the device is as follows. Since the reference signal of the multiplier 4 periodic, its spectrum consists of discrete lines (harmonics), the distance between which is equal to the T - period of the SRP. If the Central frequency of the filter 6 is equal to fFCit will get the input sinusoidal disturbance with frequency

fpack=fFC±fhi

where fhi- frequency of the i-th harmonic of the SRP. If the frequency fpacknarrowband interference such that |fpack-f0| falls into the interval fhi±P/2, where f0the carrier frequency SFMS, and P - band output filter correlator 6, we can say that the i-th harmonic of the SRP is “affected”. To prevent interfering effect of this interference, it is necessary to exclude from the reference SRP i-th harmonic.

Thus, suppression of the input narrow-band interference rejection is (with the exception) of the corresponding “amazed” harmonics from the spectrum support of the SRP. Such rejection can be done transversal filter in which the delay line has a total time delay of not less than T/2. But as you know, T=Nτewhere N is the number of elements in the period of the SRP, and τe- the duration of a single element. For large N even discrete real is within the delay line is difficult.

But in our case, the transversal filter operates with a fixed signal (SRP), therefore for the formation of delayed signals from the taps of the delay line can be used synchronized generators SRP (the generators of the 22, 23...2nfigure 2). The number of generators of the SRP is equivalent to the number of taps of the delay line in the receiver prototype. The shift of the SRP in time relative to the SRP generated by the block 2’is the initial installation of the pulse from the output of the decoder 1. Different initial state is achieved by applying the installation of the pulse at respective inputs R and S of the triggers included in generators SRP 22, 23...2n. The signals on the (m+1)-e (main) outputs of all generators SRP 21-2ncomes with (m-1)-x trigger delay τe/2.

Blocks 21-2n5 and 7 form a group of k transversal filter II with constant weights, which are chosen so that each transversal filter missed a certain set of harmonics of the SRP. In sum, these sets cover all harmonics of the SRP.

Consider one of the simplest cases, the formation of four sets of harmonics of the SRP. For this example, the General scheme of the formation of sets of harmonics of the SRP is shown in figure 3, where indicated:

SH- set the Neche the different harmonics (1, 3, 5, 7... );

Sh- the set of even harmonics(2, 4, 6, 8... );

SNN- a set of harmonics with numbers(5, 9, 13, 17... );

SLF- a set of harmonics c rooms(3, 7, 11, 15... );

sHHH- a set of harmonics with numbers(9, 17, 25... );

SNN- a set of harmonics with numbers(5, 13, 21... ).

T/2, T/4, T/8 - delay components;

∑ - adder;

Δ - subtraction scheme.

The location of the harmonics in the frequency axis shown in figure 4. Thus, the formation of a set of harmonics of SIUUis carried out according to the expression:

SIUU(t)=SNN(t)+SNN(t-T/8)=S(t)+S(t-T/2)+S(t-T/4)+S(t-3T/4)+S(t-T/8)+S(t-5T/8)+S(t-3T/8)+S(t-7T/8)

From this expression it follows the structure of the associated transversal filter shown in figure 5.

The generators of the SRP are common to all transversal filters. Other transversal filters are synthesized similarly.

It should be noted that in the present case, the weights take values ±1, so the unit of weight coefficients is not required.

The output signal from each of the k transversal filters II transit through the power of the keys 9 enters the unit of analysis and management 10, which serves as a reference to the first input of the multiplier analyzing the correlation of the channel 10.1 (7), to the second input of which receives an input mixture signal and narrowband interference.

The output signals of all the analyzing channels are compared by level, the result determines which set is “amazed”and what is not. Along with the described parallel analysis can be used, and sequential analysis. Command block 10 block 9 is closed the corresponding keys, resulting in an affected set of harmonics SRP rejections and is not sent to the reference input of the multiplier 4. Thus the suppression of narrowband interference, which do not fall into the filter 6.

In the proposed device rejections not only “affected” harmonics, and sets of harmonics, including “unaffected” harmonics. Although this leads to additional losses in the signal-to-noise ratio, but technically the device is much easier feasible.

Functional diagram generator SRP 21with the decoder 1 is presented on Fig.6.

Generator SRP 21is a shift register made on D-triggers T1T2,... Tm. The output of each of flip-flops depending on the selected code either connected or not connected with the input of the modulo 2. Feedback is provided by connecting the output of the adder modulo 2 to the input D of the first flip-flop. Depending on the initial state of the generator SRP 21the setup pulse is served either on R or on input S of the flip-flop. If the SRP (m-1)-th and m-g the triggers used in the synchronization unit 3 (figure 2), in the center (signal) channel (m+1)-th output of the generator 21comes detained on τe/2 SRP output (m-1)-th trigger.

The decoder 1 is made according to scheme I. He captures the initial state of the generator SRP 21. If the initial state selected state triggers 01000... 00 is used as a direct output of the second trigger and inverted outputs of all the others. When reaching this state, the output of the decoder 1 is formed impulse, which are defined initial state of all generators SRP 2.

Generators SRP 21-2nperformed according to the same scheme (6). Generators 22-2ndiffer from the generator 2’ the fact that they use only (m-1) flip-flop, and the other outputs are not.

Example execution of the synchronization unit 3 shown in RIS on str books: Spilker j. Digital satellite communications. TRANS. from English. Ed. You. - M.: Communication, 1979.

Unit weights 5 may be made in the form of a set of resistive attenuators.

The summation block 7 represents a typical set of adders, for example, resistive.

Key block 9 can be made according to the scheme shown in Fig. To sets of harmonics of the SRP from the outputs of the adders 7 transversal filters II received via block 9 (parallel analysis) relevant to the respective inputs of the unit of analysis and management 10 and the signal inputs of the respective keys. If the set has “affected” harmonics, of the unit 10 to the control input of the corresponding key receives the locking signal and this set is excluded from the support of the SRP, which is formed on the (k+1)-th output block of 9 keys.

The unit of comparison and control 10 can be made according to the scheme shown in Fig.7, where indicated:

10.11, 10.12...10.1kthe multiplier products;

10.21, 10.22...10.2k- bandpass filters;

10.31, 10.32...10.3k- amplitude detectors;

10.41, 10.42...10.4kintegrators;

10.51, 10.52...10.5k- threshold devices;

10.6 - unit calculation of the threshold.

The unit of comparison and control 10 consists of k parallel analyzing channels, each of which has connected in series multiplier 10.1, the first input of which is relevant (from 1 to k) of the input unit 10, the band-pass filter 10.2, the amplitude detector 10.3. the integrator 10.4 and a threshold device 10.5 whose output is the corresponding output of the unit 10, with (k+1)-th entry unit of analysis and control 10 is connected to the second inputs of the multiplier products 10.1. The outputs of the integrators 10.4 connected to respective k inputs of the computing unit threshold 10.6, the output of which is connected to the second inputs of the k threshold devices 10.5.

the address block comparison and control 10 is as follows. The inputs 1, 2... k unit 10 outputs the corresponding transversal filters II transit through key block 9 receives signals, the spectrum of which represents a specific set of harmonics of the SRP, and the (k+1)-th input signal of the input mixture signal and narrowband interference. If any set that contains an affected harmonics, the corresponding narrowband interference are part of the output of bandpass filter 10.2 of this channel, which creates a high voltage level at the output of the corresponding integrator 10.4. Based on the voltages at the outputs of integrators 10.4 all channels of the unit for computing the threshold 10.6 generates the threshold voltage. If the threshold device 10.5 the voltage output from the integrator 10.4 exceeds the threshold, the output is formed by the team, which prohibits the block of keys 9 (2) passage set with “amazed” by the organ on the reference input of the multiplier 4 (figure 2).

The receiver complex phase-shift keyed signals with suppression of narrowband interference, containing connected in series multiplier, bandpass filter and demodulator, and the block weights, unit totals, the unit of analysis and management, the synchronization unit and the first pseudo-random sequence generator (SRP), (m-1)-th and m-th outputs of which are connected with the respective reference inputs of the synchronization unit, the output of which the CSO is connected with a clock generator input SRP, when this signal input to the synchronization unit is combined with the signal input of the multiplier and (k+l)-th entry unit of analysis and control, and the output of the demodulator is the output of the receiver, characterized in that it introduced the decoder, the block keys, (n-1) generators of pseudo-random sequence clock inputs of which are connected with the output of the block sync signal input which is the input of the receiver, setting the inputs of all n generators SRP is connected to the output of the decoder, the m inputs of which are connected with the corresponding m outputs of the first pseudo-random sequence generator, and (m+1)th outputs of all n generators SRP connected to respective n inputs unit of weight coefficients, kn outputs of which are connected with the corresponding kn inputs summation block, the k outputs of which are connected with the signal k inputs of the block of keys that control the k input of which is connected with the corresponding k outputs of the unit of analysis and management, k inputs of which are connected with the corresponding k outputs of the block of keys, (k+1)-th output of which is connected to the reference input of the multiplier.



 

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