RU2700580C1 - Method for energy detection of a signal with compensation of combination signal components and interference in the main and compensation channels - Google Patents

Abstract

FIELD: communication equipment.

SUBSTANCE: invention relates to communication engineering and can be used in communication apparatus. In the method of energy detection of a signal with compensation of combination components of a signal and interference in the main and compensating channels, an additive mixture of signal and interference is branched and processed in the main and compensating channels in the same way: signal after squaring is simultaneously filtered by a low-pass filter (LPF), the band of which is matched with a signal band, and a band-pass filter (BF), in which the upper frequency corresponds to the upper frequency of the signal, and the value of the lower frequency is maximally close to zero; sums of differences of readings of signals and signals mixture passed through filters are calculated. In the compensation channel, readings of the mixture of signal and interference passed through the filters are taken with a time shift, the value of which is determined in advance. Signal amplitude value is calculated using stored values obtained in channels. Conclusion on presence of signal type is made by comparing results of signal amplitude value with corresponding threshold.

EFFECT: reduced time consumed for estimation of noise power, and thereby increased speed of information exchange in conditions of presence of noise.

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Description

The method relates to radio engineering and may find application in communications.

Known methods that are implemented by devices for suppressing narrowband interference described in AS No. 1688416 H04B 1/10, and also in the patents of the Russian Federation No. 2034403 H04B 1/10, No. 2204203 H04B 1/10, the device for the compensation of narrow-band interference described in the article by Efimov V.P. “Evaluation of the effect of nonlinear conversion on the noise immunity of reception in satellite networks”, published in the journal “Electromagnetic waves and electromagnetic systems”, No. 1, v.3, 1998, p. 95, the disadvantage of which is the low degree of noise suppression.

Known methods that are implemented by devices for suppressing broadband interference described in patents RU 2115234, H04B 1/10, RU 2143783, H04B 1/10, RU 2190297 H04B 1/10, the disadvantage of which is the low degree of interference suppression.

A known method of energy detection of Price-Urkovits described in the training manual "Fundamentals of the theory of radio systems". Tutorial. // V.I. Borisov, V.M. Zinchuk, A.E. Limarev, N.P. Mukhin. Ed. V.I. Borisova. Voronezh Scientific Research Institute of Communications, 2004, pp. 75 - 76. The disadvantage of this method is the low noise immunity of communications in the presence of interference such as additive white Gaussian noise, as well as the complexity of the practical implementation associated with the long time to estimate the interference power.

Closest to the technical nature of the proposed is a method of signal isolation in the presence of interference, described in patent RU No. 2675386 H04B 1/10, adopted as a prototype.

The prototype method consists in the fact that an additive mixture of signal and interference is processed in the linear path of the receiver, after which the signal is squared, the signal after squaring is filtered by a low-pass filter (LPF), the band of which is matched with the signal band. At the same time, the signal after squaring is filtered with a band-pass filter, the passband of which is selected so that the upper frequency of the band-pass filter corresponds to the upper frequency of the signal, the lower frequency of the band-pass filter is selected as close to zero as possible. The choice of the low-pass filter and the band-pass filter is carried out with phase-frequency characteristics identical to the maximum degree relative to each other and so that the minimum possible value of the sum of the differences of the amplitude-frequency characteristics of the low-pass filter and the band-pass filter taken for all frequencies is ensured. The samples of the signals that have passed the bandpass filter and the low-pass filter are formed in digital form, by conversion in the corresponding analog-to-digital converters (ADCs), these values are subtracted from one another in the computing device, the obtained values are added up and stored, the interference power value is subtracted from the resulting amount, which is obtained as follows — filter the interference with the same low-pass filter that filters the signal and noise mixture, at the same time filter the noise with the same band-pass filter that filters the signal and noise mixture, forming digital comfort, by converting to the appropriate ADCs, samples of the interference that passed the low-pass filter and a band-pass filter, these values are subtracted from one another, the obtained values are summarized and stored, this value of the interference power is obtained during the time interval of the interference analysis, which is located immediately before the processed information symbol, and which contains only interference, decide on the presence of a signal by comparison with a threshold.

The disadvantage of the prototype method is that in order to provide an estimate of the interference power, a time interval is formed in which the signal is obviously absent, which leads to a decrease in the rate of information exchange.

The task is to reduce the time spent on estimating the interference power, and thereby, increasing the information exchange rate in the presence of interference, including the type of additive white Gaussian noise (ABGS).

To solve the problem in the method, namely, that the additive mixture of signal and interference is processed in the linear path of the receiver, after which the signal and interference mixture are squared, after squaring the received signal, filter the low-pass filter (low-pass filter), the band which is consistent with the signal band; at the same time, the received signal is filtered by a band-pass filter, the passband of which is selected so that the upper frequency of the band-pass filter corresponds to the upper frequency of the signal, the lower frequency of the band-pass filter is selected as close to zero as possible; the choice of the low-pass filter and the band-pass filter is carried out with the maximum identical phase-frequency characteristics relative to each other and so that the minimum possible value of the sum of the differences in the amplitude-frequency characteristics of the low-pass filter and the band-pass filter taken for all frequencies is provided; digitally generated by conversion in the corresponding analog-to-digital converters (ADCs), samples of signals that have passed the band-pass filter and low-pass filter, these values are subtracted from one another in the computing device, the obtained values are summed and stored, according to the invention, they use binary amplitude-modulated ( AMn) signal, the amplitudes of various signals (of various types) differ by a specified number of times; the signal and noise mixture are branched at the output of the receiver’s linear path; in the compensation channel, the signal and noise mixture are processed as in the main channel, namely: the received signal is simultaneously filtered in the main channel by a low-pass filter (LPF), the band of which is matched to signal band; at the same time, the received signal is filtered by a band-pass filter, digitally formed by conversion to the corresponding ADCs, samples of signals that have passed the band-pass filter and low-pass filter, these values are subtracted from one another in the computing device, the obtained values are stored, while the samples of signals that have passed the band-pass and low-pass filters , take with a time shift relative to the samples of the main channel, the value of which is determined in advance, the sum of the differences of the samples of signals that have passed the band-pass filter and the samples of signals After the low-pass filter is stored, the signal amplitude is calculated using the stored voltage values obtained in the main and compensation channels, the conclusion about the presence of a signal of the first or second type is made by comparing the obtained signal amplitude with a corresponding threshold.

The proposed method is as follows.

The method is described for the case of using amplitude-modulated (AMn) signals and operation at a fixed frequency. For the case of operation with frequency tuning, the process is carried out for each operating frequency in the same way as for a fixed frequency.

Two types of signal are generated. Signals of various types differ in that their amplitudes differ by a specified number of times:

K _oa = U ₁ / U ₂ , (1)

where: K _oa - the value of the ratio of the amplitudes of the signals of various types;

U ₁ , U ₂ - the amplitudes of the signals of the first and second type.

It is believed that when entering the connection, synchronization is made, and the position in time of the start of the signal is known with sufficient accuracy to subtract and sum the signals with the necessary efficiency.

A predetermined efficiency level means that the probability of signal detection will be no less than a predetermined level, while the probability of a false alarm does not exceed a predetermined level.

After processing, a voltage equal to the sum of the squares of the signal amplitudes and the interference components is obtained in the main channel

, (2)U ₁ = K _prs U ² _s + K _prp

, (2)

where: U _with - the amplitude of the signal;

Nsp is the number of harmonic noise components used to represent it (approximation);

– амплитуда i-ой составляющей помехи;

- the amplitude of the i-th component of the interference;

K _prs , K _prp - the coefficients of signal conversion and interference when squaring the sum of the signal and interference.

The values of the signal and interference conversion coefficients when squaring the sum of the signal and the interference are determined experimentally at the stage of development of a communication tool.

As sources of interference are considered, for example, any radio transmitting means, industrial interference caused by the operation of various electrical installations, as well as atmospheric interference. These interferences affect the operation of radio receivers. The interference during simulation is presented as a set of harmonic oscillations with random values of amplitudes (U _pi ) and phases (ϕ _pi ), which are distributed according to normal (amplitudes) and uniform (phases) laws (see, for example, the training manual “Fundamentals of the theory of radio engineering systems ". Textbook. // V.I. Borisov, V.M. Zinchuk, A.E. Limarev, N.P. Mukhin. Edited by V.I. Borisov. Voronezh Telecommunications Research Institute, 2004., p. 51, 68)

, (3)U =

, (3)

where: ω _pi , φ _pi - frequency and phase of the i-th component of the interference, respectively.

It is believed that for an ABGSh type interference, the lifetime of the interference components is less than the time interval for taking samples in an analog-to-digital converter (ADC), i.e. interference samples are independent random variables.

A mixture of signal and interference at the output of the receiver linear path is branched. In the compensation channel, the signal processing is carried out in the same way as in the main channel, while the samples of signals that have passed the band-pass filter and low-pass filter are taken with a time shift, the value of which is determined in advance.

The value of the time shift is set on the basis of the conditions for ensuring a given level of efficiency of separation of signals of various types at the development stage by mathematical modeling or experimentally.

From the samples of signals that have passed the bandpass filter, subtract the samples of signals that have passed the low-pass filter. The obtained values are summarized and stored. In this case, a voltage is obtained equal to the sum of the squares of the amplitudes of the interference components and the signal amplitudes, changed by a value whose value depends on the value of the time shift of the sampling (see Fig. 1)

, (4)U ₂ = K _s K _prs U ² _s + K _prp

, (four)

where: K _with - the magnitude of the change in the square of the amplitude of the signal, the value of which depends on the value of the time shift of the sampling signal.

Denoting in equalities (2) and (4)

, (5)P ² =

, (5)

we get a system of two equations with two unknowns

U ₁ = K _prs U ² _s + K _prp R ² ,

U ₂ = K _s K _prs U ² _s + K _prp R ² . (6)

Solving this system of equations for U ² _with we get

U ² _s = (U ₁ -U ₂ ) / (K _prs -K _with K _prs ). (7)

Applying f. (7) calculate the signal amplitude value using the stored voltage values obtained in the main and compensation channels.

If the shift time of sampling the signal in the compensation channel is set to T / 4,

where T is the value of the period of the frequency change at which the processing is carried out (see figure 1), then in this case

U ² _s = 0.

Then f. 7 can be written as

U ² _s = (U ₁ -U ₂ ) / K _prs . (8)

The conclusion about the presence of a signal of the first or second type is made by comparing the obtained value of the signal amplitude with the corresponding threshold.

The threshold value is determined, for example, using a reference signal, which is transmitted before the transmission of messages.

The results of evaluating the effectiveness of the proposed method were obtained by mathematical modeling on a computer using the MATLAB system.

When modeling, the following initial data were used:

- the number of implementations - 10 ³ ;

- type of manipulation - amplitude manipulation;

- the ratio of the amplitudes of the signals (U ₁ / U ₂ ) - 1.5;

- the ratio of the values of the upper frequency of the signal band to the lower frequency of the signal is 1.1;

- the number of samples per period when evaluating the power of the signal mixture and interference when using the prototype method and when using the proposed method - 2;

- the number of signal periods is 3;

- the number of harmonic components of the interference used to represent it is 10 ³ ;

- K _prs - 0.5;

- K _s - 0.2;

- the probability of correct detection is 0.999;

- the probability of a false alarm is 10 ^-3 .

The simulation results for interference type ABGS are shown in the table.

K _p Parameter Name Parameter value The ratio of interference power and signal 80% Qps 1.3 Qts 1.28 Qps / Qts 1,02

The following notation is used in the table:

K _p - coefficient of suppression of the combination components of the interference and signal and interference (%);

Q _ps - the ratio of the power of interference and signal for the proposed method;

Q _tf - the ratio of the interference power and signal for the prototype method;

Q _ps / Q _tf - the ratio of the power of interference and signal for the proposed method and the prototype method.

Analysis of the data given in the table allows us to conclude that the effectiveness of the proposed method is practically not inferior to the effectiveness of the prototype method under the influence of interference type ABGSh. When the rate of change of the interference power is comparable with the value of the period of change of the signal frequency, the information exchange rate using the proposed method can be almost doubled compared with the case of the prototype method.

Thus, the use of the proposed method allows to increase the speed of information exchange due to the fact that the assessment of the interference power and the sum of the signal and interference are carried out almost simultaneously.

The structural diagram of a device that implements the proposed method is shown in FIG. 2, where indicated:

1 - intermediate frequency amplifier (UPCH);

2.1, 2.2, 2.3, 2.4, 2.5 - from the first to fifth splitters;

3.1, 3.2 - the first and second blocks of multiplication;

4.1, 4.2 - the first and second low-pass filters (low-pass filters);

5.1, 5.2, 5.3, 5.4 - from the first to the fourth analog-to-digital converters (ADC);

6.1, 6.2 - the first and second band-pass filters (PF);

7 - computing device (WU).

The device comprises a serially connected converter 1, a first splitter 2.1, a second splitter 2.2, a first multiplier block 3.1, a third splitter 2.3, a first low-pass filter 4.1, a first ADC 5.1 and a computing device 7, the output of which is the output of the device, while the second output of the second splitter 2.2 is connected with the second input of the first block of multiplication 3.1. The second output of the third splitter 2.3 through a series-connected first PF 6.1 and the second ADC 5.2 is connected to the second input of the computing device 7. The second output of the first splitter 2.1 through a series-connected fourth splitter 2.4, the second multiplication block 3.2, the fifth splitter 2.5, the second low-pass filter 4.2 and the third ADC 5.3 is connected to the third input of the computing device 7. The second output of the fourth splitter 2.4 is connected to the second input of the second multiplication block 3.2. The second output of the fifth splitter 2.5 through a second PS and a fourth ADC 5.4 connected in series is connected to the fourth input of the computing device 7. The input of the IF 1 is the input of the device. The input of the first splitter 2.1 is the input of the main processing channel. The outputs of the first 5.1 and second 5.2 ADCs are respectively the first and second outputs of the main channel. The input of the fourth splitter 2.4 is the input of the compensation processing channel. The outputs of the third 5.3 and fourth 5.4 ADCs are respectively the first and second outputs of the compensation channel.

The device operates as follows.

A description is given of a method for the case of operation at a fixed frequency. For the case of operation with frequency tuning, the process is carried out for each operating frequency in the same way as for a fixed frequency.

A harmonic signal is used. The type of modulation is amplitude manipulation (AMN).

Two types of signal are generated. Signals of various types differ in that their amplitudes differ by a specified number of times f. (one).

It is believed that when entering the connection, synchronization is carried out, and the position in time of the beginning of the signal is known with sufficient accuracy to take samples with the necessary accuracy.

An additive mixture of signal and interference is processed in the receiver linear path, after which it is fed from the output of the amplifier 1 to the first splitter 2.1, where the signal and interference mixture are branched into two identical components. The first component is fed into the second splitter 2.2, where the signal and interference mixture are branched into two identical components, which are fed respectively to the first and second inputs of the first multiplication block 3.1. The result of squaring the mixture of signal and interference (hereinafter referred to as the signal) is fed to the third splitter 2.3, where it is branched into two identical components. The first component is filtered by the first low-pass filter 4.1, the band of which is consistent with the signal band. The second component is filtered by the first PF 6.1, the passband of which is selected so that the upper frequency of the bandpass filter corresponds to the upper frequency of the signal, the lower frequency of the PF 6.1 is selected as close to zero as possible. The selection of the first 4.1 and second 4.2 low-pass filters and the first 6.1 and second 6.2 band-pass filters is carried out with the maximum phase-frequency characteristics identical to each other and so that the minimum possible value of the sum of the differences in the amplitude-frequency characteristics of the low-pass filters and band-pass filters taken for all frequencies. The signal from the output of the first low-pass filter 4.1 is fed to the first analog-to-digital converter (ADC) 5.1. The signal from the output of the first PF 6.1 is fed to the second ADC 5.2. In the first 5.1 and second 5.2 ADCs form the signal samples in digital form. The signal samples from the outputs of the first 5.1 and second 5.2 ADCs are fed respectively to the first and second inputs in WU 7, in which the samples of the signal transmitted to the output of the first PF 6.1 are subtracted from the samples of the signal transmitted to the output of the first low-pass filter 4.1. The obtained values are summarized and stored.

In the compensation channel, the signal processing is carried out in the same way as in the main channel, while the samples of the signals that passed the second low-pass filter 4.2 and the second PF 6.2, which form in the third ADC 5.3 and the fourth ADC 5.4, respectively, are taken with a time offset, the value of which is determined in advance ( see Fig. 1).

In WU 7, the difference between the samples of the signals passing the second low-pass filter 4.2 and the samples of the signals passing the second PF 6.2 are calculated, these values are summarized and stored. The signal amplitude value is calculated using the stored voltage values obtained in the main and compensation channels using f. (7).

The conclusion about the presence of a signal of the first or second type is made by comparing the obtained value of the signal amplitude with the corresponding threshold.

The threshold value is determined, for example, using a reference signal, which is transmitted before the transmission of messages.

The results of evaluating the effectiveness of the proposed method were obtained by mathematical modeling on a computer using the MATLAB system.

The simulation results are given in the corresponding description table.

UPCH 1 can be implemented, for example, on the AD8054ARUZ chip from Analog Devices.

From the first 5.1 to the fourth 5.4 ADCs can be implemented, for example, on the Texas Instruments ADS8422 chip.

Computing device 7 can be made in the form of a programmable logic integrated circuit (FPGA), and is implemented, for example, on the XC2V3000-6FG676I chip from Xilinx.

Thus, when using the proposed method and device that implements it, the effectiveness of the proposed method is practically not inferior to the effectiveness of the prototype method under the influence of interference type ABGSh. When the interference power is changed at a speed commensurate with the period of the signal frequency, the information exchange rate is almost doubled, compared with the case of the prototype method, due to the fact that the interference and signal powers are evaluated simultaneously.

Claims (1)

The method of energy detection of a signal with compensation of the combination components of the signal and interference in the main and compensation channels, which consists in the fact that the additive mixture of signal and interference is processed in the receiver linear path, after which the signal and interference mixture are squared, after squaring the received signal is filtered low-pass filter (low-pass filter), the band of which is consistent with the band of the signal; at the same time, the received signal is filtered by a band-pass filter, the passband of which is selected so that the upper frequency of the band-pass filter corresponds to the upper frequency of the signal, the lower frequency of the band-pass filter is selected as close to zero as possible; the choice of the low-pass filter and the band-pass filter is carried out with phase-frequency characteristics identical to the maximum degree relative to each other and so that the minimum possible value of the sum of the differences in the amplitude-frequency characteristics of the low-pass filter and the band-pass filter taken for all frequencies is provided; digitally form by converting in the corresponding analog-to-digital converters (ADCs) samples of signals that have passed the band-pass filter and low-pass filter, these values are subtracted from one another in the computing device, the obtained values are summed and stored, characterized in that they use binary amplitude-modulated ( AMn) signal, amplitudes of signals of various types differ by a specified number of times; the signal and noise mixture at the output of the receiver linear path is branched, in the compensation channel the signal and noise mixture are processed in the same way as in the main channel, namely: the received signal is simultaneously filtered in the main channel by a low-pass filter (LPF), the band of which is matched with a signal band; at the same time, the received signal is filtered by a band-pass filter, digitally generated by conversion to the appropriate ADC samples of signals that have passed the band-pass filter and low-pass filter, these values are subtracted from one another in the computing device, the obtained values are stored, while the samples of signals passed the band-pass and low-pass filter, take with a time shift relative to the samples of the main channel, the value of which is determined in advance, the sum of the differences of the samples of signals that have passed the band-pass filter and the samples of signals Shih LPF is stored, computed value of the signal amplitude using the stored voltage values obtained in the ground and the compensation channels, the output signal the presence of the first or of the second type do result by comparing the obtained values of signal amplitude with a corresponding threshold.

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