RU2700798C2 - Apparatus for detecting broadband polyharmonic signals on background of additive interference - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention relates to radio electronics and hydroacoustics, namely to devices for detecting signals in the presence of interference. Device allows increasing noise immunity due to use and inclusion of a correlator into the scheme of the invention, which, by memorizing successful incoming responses, can detect a signal with a minimum signal-to-interference value. Invention is based on the use of quadrature detection in each frequency channel of the passive system instead of conventional energy detectors based on quadratic detection. Distinctive feature is addition of correlator after signal processing by prototype, which allows additional processing of responses of several polyharmonic signals considered as single signal (analogue of signal packet, as in time domain), which is based on the need to ensure constant filter duty ratio, and to

times improve the signal interference ratio (where m is the number of poly-harmonic signals (analogue for narrow-band factor -

, which must be observed in the entire frequency range).

EFFECT: enabling detection of signals with a minimum signal-to-interference value, as well as high noise-immunity higher than the signal-to-interference ratio with the established probability of detecting signals.

1 cl, 8 dwg

Description

The present invention relates to the field of radio electronics, namely, to devices for detecting broadband signals (with a spectral power density in the form of individual discrete components of a polyharmonic signal) against the background of additive interference. The main task of the receiving part of the signal detection system is to decide on the presence or absence of a useful signal from the object in the observed input process.

The problem is solved due to the fact that a threshold is set in the receiver, selected on the basis of one of the statistical criteria for the given probabilities of correct detection and false alarm, to which the highest requirements are imposed, because Signal detection typically occurs with minimal signal-to-noise ratios.

The technical result achieved consists in the possibility of detecting signals with a minimum signal-to-noise value, as well as in increasing the noise immunity above the signal-to-noise ratio with the established probability of signal detection. The high efficiency of this device, the ability to detect a signal with a low signal-to-noise value causes a high economic benefit, which can be used when implementing sonar signals in a processing system.

Prototype. Currently, to solve this problem, the most widely used are the so-called passive broadband and narrowband sonar systems [1, 5, 6]. Of the previous devices, the most interesting device is the detection of narrow-band noise hydroacoustic signals based on a quadrature receiver (prototype; patent No. 2549207 of 03/26/2015). The operation diagram of the device is shown in FIG. one,

Where:

block 1 - analog-to-digital Converter (ADC);

block 2 - recirculator;

blocks 3.1 - 3.M - a set of digital narrow-band bandpass filters (UPF) that cover the expected frequency range, with different bandwidths and different center frequencies, but with a constant filter duty cycle (the ratio of the filter band to its center frequency) in the entire frequency range, namely

Or, given that ω = 2πf

The average frequency in each filter is determined by the expression

blocks 4.1 - 4.2M - multipliers;

block 5 - ROM;

blocks 6.1 - 6.2M - integrators;

blocks 7.1 - 1.2M - quadrators;

blocks 8.1 - 8.M - adders;

blocks 9.1 - 9.M - square root calculators;

blocks 10.1 - 10.M - delay devices

block 11 - adder;

block 12 is a threshold device;

block 13 is a control device.

Condition (1) can be met only if the number of degrees of freedom of each component of the polyharmonic signal is the same. Condition (1) means that the filters for each component are of equal quality. For example, if for frequency f ₀

Фиг. 2corresponds to the duration τ, then at a frequency of 2 f ₀ corresponds

FIG. 2

The principle of operation of the device is as follows: the incoming implementation of the input process is sent to the ADC input (block 1), where it is received in the form of discrete samples at the input of the recirculator (block 2), where the current discrete sample is generated and updated. Further, this sample goes simultaneously to the inputs of M narrow-band filters (blocks 3.1 - 3.M), where at the same time the pairs of multipliers (blocks 4.1 - 4.2M) arrive at the first inputs of M, from the outputs of which the results go to integrators (blocks 6.1 - 6.2M ) Then, the sine and cosine components of the digital signals from the ROM (block 5) arrive at the second inputs of the M pairs of multipliers (blocks 4.1 - 4.2M). After M pairs of integrators exit (blocks 6.1 - 6.2M), the results are fed to the inputs of the quadrators (blocks 7.1 - 7.2M), after which they arrive at the inputs of the M adders (blocks 8.1 - 8.M), and the summation results are then sent to inputs of M square root calculators (blocks 9.1 - 9.M). Later, the calculation results are fed to the inputs of the M delay devices (blocks 10.1 - 10.M), to ensure the condition (1), and the outputs of this device receive responses from the inputs of the adder (block 11). Then, the summation results are sent to the input of the threshold device (block 12), the output of which is the output of the device. The control device (block 13) synchronizes the operation of an analog-to-digital converter (block 1), a recirculator (block 2), a ROM (block 5) and a threshold device (block 12).

The analogue. Also known is a method that is a sequential execution of operations: multi-channel narrow-band bandpass filtering (for the formation of individual frequency channels), quadratic detection, integration and comparison with a threshold. This device (analog) [1, p. 351-352], which implements the indicated narrowband noise detection method, is shown in FIG. 3

Where:

block 1 - analog-to-digital Converter (ADC);

block 2 - recirculator;

blocks 3.1 - 3.M - a set ("comb") of digital narrow-band bandpass filters (UPF), with the same bandwidth and different center frequencies (with a uniform frequency step equal to the bandwidth of one filter);

blocks 7.1 - 7.M - quadrators;

blocks 6.1 - 6.M - integrators;

block 12 is a threshold device.

The principle of operation of this device is as follows: the input of the device receives the implementation of the input process, which is fed to the input of the ADC (block 1). The output of the ADC is a sequence of pulses at intervals satisfying the requirements of Kotelnikov’s theorem:

f _in - the upper frequency of the signal spectrum in the filter band;

Δt is the sampling interval

From the ADC output (block 1), discrete samples go to the recirculator input (block 2), where the current discrete sample x (n) of length N samples is generated and updated with each new sample. The generated current discrete sample of the input process x (n) is fed simultaneously to the inputs of M digital narrow-band filters (blocks 3.1 - 3.M) (M - channel comb UPF), where M of individual frequency channels are formed.

The formed (filtered) narrow-band noise processes go to the inputs of the quadrators (blocks 7.1 - 7.M), from the outputs of which squared narrow-band signals go to the inputs of the integrators (blocks 6.1 - 6.M). The integration time (or accumulation) of narrow-band signals is usually chosen equal to the value inversely proportional to the bandwidth of the UPF [1], and providing potential frequency resolution for this spectral analysis method (filtering method). From the outputs of the integrators, the selected responses arrive at the input of the threshold device (block 12), the output of which is the output of the device.

Under real conditions of receiving a polyharmonic signal against the background of interference, the determinism of the useful signal cannot be discussed, since (at least) the initial phase of the signal in the processed sample of the input process, limited in time, is unknown. In this case, it is proposed to use the optimal signal receiver with an unknown initial phase (quadrature detector) as a detecting element (optimal receiver) of a passive narrowband system.

) и равно N, то на выходе прототипа, отношение сигнал-помеха (ОСП) для каждой компоненты равна

Поэтому после обработки сигналов может быть несколько откликов. Если принять, что число компонент в каждом полигармоническом сигнале одинаково (ниже покажем, что это несложно обобщить на случай если число компонент различно) и равно n, то после обработки ОСП увеличится для каждого полигармонического сигнала в

соответственно отношение сигнал помеха будет иметь следующий вид

Полученные отклики можно рассматривать как пачку сигналов в спектральной области. Частотный интервал между ними можно рассматривать как аналог скважности. Эту пачку откликов можно запомнить в виде копии в устройстве запоминания в виде опорного сигнала. Если, к примеру, таких полигармонических сигналов m, то после сравнения запомненной копии с реализацией после обработки совокупности полигармонических сигналов отношение сигнал-помеха увеличится

раз. Таким образом, общий выигрыш в ОСП составит

На практике при обработке нескольких полигармонических сигналов возможны ситуации, при которых во входном очередном процессе будет минимальное значение сигнал-помеха, что может привести к отсутствию отклика на выходе вышеописанного устройства. В этом случае, отклик выше порога может быть получен после следующего этапа обработки. Пошагово алгоритм обработки можно представить в следующем виде.The proposed device. As a rule, in a noise portrait of an object there are several polyharmonic signals, each of which is generated by its source, which is not connected with the others, if at the input it is assumed that the number of degrees of freedom for each component of the received signal is constant (which is equivalent to

) and equal to N, then at the output of the prototype, the signal-to-noise ratio (SIR) for each component is equal to

Therefore, after processing the signals, there may be several responses. If we assume that the number of components in each polyharmonic signal is the same (below we show that it is easy to generalize to the case if the number of components is different) and is equal to n, then after processing the SIR will increase for each polyharmonic signal in

accordingly, the signal-to-noise ratio will have the following form

The received responses can be considered as a packet of signals in the spectral region. The frequency interval between them can be considered as an analogue of duty cycle. This response packet can be remembered as a copy in the memory device in the form of a reference signal. If, for example, there are m such polyharmonic signals, then after comparing the stored copy with the implementation, after processing the set of polyharmonic signals, the signal-to-noise ratio will increase

time. Thus, the total gain in the OSB will be

In practice, when processing several polyharmonic signals, situations are possible in which the input next process will have a minimum signal-to-noise value, which may lead to a lack of response at the output of the above-described device. In this case, a response above the threshold can be obtained after the next processing step. Step-by-step processing algorithm can be represented as follows.

, i=1,2,3…n., N-число степеней свободы. Фиг. 4.1. At the first stage, an implementation consisting of several polyharmonic signals is accepted (in the case under consideration, 3. We set

, i = 1,2,3 ... n., N-number of degrees of freedom. FIG. four.

2. At the second stage, the signal is processed by the prototype. As a result, we will have an OSB for each response

Фиг. 5

FIG. 5

3. At the third stage, if the responses of the polyharmonic signals are highlighted, the distances between them in frequency (analogue of the duty cycle) are calculated and entered into the memory as a reference.

4. At the fourth stage, the stored copy (reference) is compared with the result of processing at the third stage. As a result, we get a gain in the OSB, which can be represented in the form of the following expression. FIG. 6

, для случая

Пояснительная схема представлена на Фиг. 7

for the case

An explanatory diagram is shown in FIG. 7

During the implementation of the proposed detector of polyharmonic signals, a number of problems were solved related to the need to ensure a constant ratio of the component band to its center frequency (filter duty cycle) in the entire frequency range and the accumulation of responses from several detector channels (summing the output processes) based on time matching analysis, i.e. the introduction of time delays at the outputs of the channels before the operation of summation. Thus, the expected positive effect when implementing this device for detecting broadband polyharmonic signals in comparison with traditional ones is achieved by using a larger amount of a priori information about the detected useful signal.

Thus, the noise immunity of the prototype can be increased by using posterior data on the properties of a complex polyharmonic signal consisting of several polyharmonic signals, i.e. dedicated receiver responses that exceed the set threshold. Using the correlator for further processing, the selected responses can be used as a reference signal. In the correlator, a quantitative assessment is made of the degree of similarity of the responses of the next discrete sample to the previous one, which allows the principle of consistent filtering to be implemented, and to increase the noise immunity of the prototype circuit.

In this case, additional information is the totality of responses from several polyharmonic signals and the frequency distances measured between them (an analogue of the duty cycle in time). On the other hand, the set of polyharmonic signals has a more complex structure and therefore if this structure is known, then there will naturally be a gain in the SIR.

The operation scheme of the proposed device based on the prototype is shown in FIG. 8,

Where:

block 1 - analog-to-digital Converter (ADC);

block 2 - recirculator;

blocks 3.1 - 3.M set of digital narrow-band bandpass filters (UPF);

blocks 4.1 - 4.M - multipliers;

block 5 - ROM;

blocks 6.1 - 6.M - integrators;

blocks 7.1 - 7.M - quadrators;

blocks 8.1 - 8.M - adders;

blocks 9.1-9. M - square root calculators;

blocks 10.1 - 10.M - delay devices;

block 11 - adder;

block 12 is a threshold device,

block 13 is a control device.

additionally included blocks:

block 14 storage device; block

15 - correlator;

block 16 - the first switching device;

block 17 - the second switching device.

block 19 - control unit switches;

The device operates as follows:

The input of the device receives the implementation of the input process x (t), which is fed to the ADC input (block 1) with a sampling frequency that satisfies the requirements of Kotelnikov's theorem:

From the ADC output (block 1), discrete samples go to the recirculator input (block 2), where the current discrete sample x (n) of length N samples is generated and updated with each new sample.

The generated current discrete sample of the input process x (n) is supplied simultaneously to the inputs of M narrow-band filters (blocks 3.1 - 3.M). From the outputs of M narrow-band filters (blocks 3.1 - 3.M), the corresponding narrow-band processes simultaneously arrive at the first inputs of M pairs of multipliers (blocks 4.1 - 4.2M), from the outputs of which the results of multiplication are fed to the inputs of M pairs of integrators (blocks 6.1 - 6.2M )

From the ROM (block 5), M pairs of sine and cosine components (monochromatic) digital signals with frequencies corresponding to the central frequencies of the UPF f _m are received at the second inputs of M pairs of multipliers (blocks 4.1 - 4.2M).

From the outputs of M pairs of integrators (blocks 6.1 - 6.2M), the results of integration are supplied to the inputs of M pairs of quadrators (blocks 7.1 - 7.2M), from the outputs of which the squares of the responses are coupled to the inputs of the M adders (blocks 8.1 - 8.M), from the outputs where the summation results go to the inputs of the M square root calculators (blocks 9.1 - 9.M), the outputs of which the calculation results go to the inputs of the M delay devices (blocks 10.1 - 10.M). From the outputs of M delay devices (blocks 10.1 - 10.M). From the outputs of the M delay devices (blocks 10.1 - 10.M), the responses arrive at the inputs of the adder (block 11), from the output of which the responses arrive at the switching devices (blocks 16, 17, 18), and the switching devices on the first cycle (block 17, 18 ) are closed, after passing through the switching device (block 16), the response arrives at the threshold device (block 12) where a decision is made on the presence or absence of a useful signal, after which, if there is a signal, information is sent to the output of the device and a command is sent to the input of the control device (block 19) ) which gives a command to close the first switching device (block 16) and the second switching device (block 17) and record the received implementation in the storage device (block 14), with the arrival of the next implementation, the second cycle begins if a threshold device (block 12) decides whether signal cycle 1 is repeated, in the case of a decision on the absence of a useful signal in the threshold device (block 12) in the control device (block 19) receives a command about the absence of a useful signal from which a command to close The term first switch (block 16) and the second switch (block 17) and for issuing command recorded implement from the storage device (block 14) to the correlator (block 15). Third cycle: With the arrival of the next implementation from the adder (block 11), through the open third switch (block 18), the stored copy (standard) is correlated with the processing result, the result is sent to the second input of the threshold device (block 12), and is output devices and the input of the control device (block 19) and the cycle is repeated as in the first cycle, otherwise the control device disconnects the keys and the circuit operates in prototype mode until several scale sounds appear again.

List of sources used

1. Butyrsky E.Yu., Smagulov A.B., Shatalov G.V., Yakunin K.V. A device for detecting noise hydroacoustic signals based on a quadrature receiver. Patent for invention No. 2549207 dated March 26, 2015 (Prototype)

2. Burdik V.S. Analysis of sonar systems. L .: Shipbuilding, 1988, p. (Analogue, p. 351-352).

3. Bolgov B.M., Plakhov DD, Yakovlev V.E. Acoustic noise and interference on ships. L .: Shipbuilding, 1984, 192 p.

4. Butyrsky E.Yu. The uncertainty function of signals on a transformation group. Information and space. 2008. No3. from. 31-39.

5. Van Tris, G., Theory of Detection, Estimation, and Modulation, vol. 1, Moscow: Sov. Radio, 1972, 744 p.

6. Van Tris, G., Theory of Detection, Estimation, and Modulation, vol. 3, Moscow: Sov. Radio 1977, 661 pp.

7. Zaraisky B.A., Tyurin A.M. The theory of sonar. L .: VMA, 1975, 604 p.

8. Olshevsky V.V. Statistical methods in sonar. L .: Shipbuilding, 1983, 280 p.

9. Urik R. J. Fundamentals of hydroacoustics. L .: Shipbuilding, 1978, 446 p.

Claims (1)

A device for detecting broadband polyharmonic signals based on a quadrature receiver, containing an analog-to-digital converter, the input of which is supplied with an input signal, and the output of which is connected to the input of the recirculator, the output of which is connected to the inputs of M narrow-band filters, the outputs of M narrow-band filters are connected to the first inputs of M pairs multipliers, the outputs of which are connected to the inputs of M pairs of integrators, the outputs of which are connected to the inputs of M pairs of squares, the outputs of which are paired with the inputs of M adder Whose outputs are connected to inputs of M square root calculators whose outputs are connected to inputs of M delay units, outputs of which are connected to M inputs of the adder, whose output is connected to the input of the threshold device, whose output is the output of the apparatus; 2M outputs of read-only memory connected to the second inputs of M pairs of multipliers; the outputs of the control device are connected to the control inputs of the analog-to-digital converter, recirculator, read-only memory and threshold device, characterized in that in order to increase the noise immunity and prototype efficiency, the adder output is connected to the first input of the second switch and the input of the third switch and the first input of the first switch, the output of which is connected to the first input of the threshold device, the output of which is the output of the device and connected to the input of the control device the first input of which is connected to the second input of the second switch, the output of which is connected to the first input of the storage device, the second input of which is connected to the second output of the control device, the third output of which is connected to the second input of the first switch, the output of the storage device is connected to the second input of the correlator, the first input of which is connected to the output of the third switch, the output of the correlator is connected to the second input of the threshold device.

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