RU2504088C1 - Method of detecting signals without carriers - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: method of detecting signals without a carrier involves dividing a digitised analogue signal into fragments which correspond to the number of elements of a predetermined digital sequence vector (DSV), inverting fragment readings, the number of which is determined based on a predetermined DSV consisting of N zero and unit values, wherein DSV values equal to zero correspond to fragments, the values of readings of which when inverted fully match values of readings of fragments corresponding to DSV values equal to one, after which a resultant sample is formed by arranging first readings of all fragments first, then second values and the last values at the end; the noise level threshold value selected is a value equal to double the mean-square deviation of readings of the resultant sample for positive and negative values of readings. Signal parameters are evaluated by comparing the sample with the noise level threshold value, wherein the signal parameters are maximum negative and positive values of the resultant sample, and a signal is detected if at least one of the parameters exceeds the threshold noise level on magnitude.

EFFECT: high reliability of detection.

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Description

The invention relates to radio engineering, and in particular to methods for detecting signals under conditions of low signal-to-noise ratio (SNR) and can be applied in ultra-wideband (UWB) short-pulse communication systems using bi-phase shift keying (BPSK - Bi-Phase Switch Key) ( see Kalinin V.O., Nosov V.I. Evaluation of parameters of a short-pulse ultrawideband communication system, Vestnik SibGUTI, 2011. No. 3, pp. 73-85).

A known method for detecting signals implemented in the detectors described in the book of Levine B.R. Theoretical Foundations of Statistical Electrical Engineering M .: Sov. Radio, 1968, p. 345-346, Fig. 26.

The method is based on non-linear processing of the implementation of the input sample and consists in the following. The input implementation is decomposed into quadrature components, which are filtered using two filters, matched with the signal components. Then the sums and differences of the input values are formed in each group of filters, which are subjected to two half-period quadratic detection. The detection results are summarized and compared with a threshold level. The decision to detect a signal is made if the sum of the detected threshold level values is exceeded.

The disadvantage of the analogue method is that it is acceptable only in cases of detection of relatively narrowband signals with known parameters.

A known method for detecting narrowband signals implemented in the signal detector according to patent RU No. 2110150 C16 H04B 1/10, G01S 7/292 from 01/23/97

In the known method, an analog signal is received, digitized, for which the operations of sampling, quantization and coding are sequentially performed. Then, the parameters of the digitized signal are calculated, for which a digitized signal is formed, shifted from the original one clock cycle, and the correlation coefficient between the original signal and its shifted version is calculated. The results of correlation processing are selected as parameters of the digitized signal. After that, the calculated parameters of the digitized signal are compared with the decision threshold, which is calculated using additional information about the expected value of the detected signal, the noise variance, and the threshold value. The decision on the fact of signal detection is made if the parameters of the digitized signal exceed the decision threshold.

The disadvantage of this method is the narrow scope, since its implementation is possible only with known parameters of noise and detectable narrowband signals.

The closest analogue in technical essence to the claimed one is the method for automatic detection of narrowband signals described in the patent of the Russian Federation No. 2382495 C1 of 02.20.2010

In the closest analogue, an analog signal is received, digitized, for which the operations of sampling, quantization and coding are sequentially performed. Then, the parameters of the digitized signal are calculated, for which they form their spectral representation by performing the Fourier transform on it. After that, the threshold noise level is calculated by calculating the double value of the sample average components of the spectral representation and the levels of each of the spectral components from the sequence of the spectral representation are estimated by comparing them with the calculated threshold noise level. Then the first and second sequences are formed, respectively, from the spectral components that exceed the threshold noise level and do not exceed it. After that, the components in the first and second sequences are separately summed up and the ratio of the found sums is calculated. Then, the ratio of the found amounts is compared with a predetermined threshold value. The decision on the fact of signal detection is made provided that the ratio of the found sums exceeds a predetermined threshold value.

The disadvantage of this analogue method is the relatively narrow scope of its application, since it does not allow reliable detection of short-term single signals without a carrier (COSN) within the frame. A frame is a temporary fragment, within which there is only one useful COSN. [cm. Chelyshev V.D., Potapov S.G., Fokin A.O. UWB - initial representations in the time and spectral domains // Information. Space No. 1, 2007, S. 45-59].

The purpose of the claimed technical solution is to develop a method that expands its scope for COSN in additive noise of high intensity.

This goal is achieved by the fact that in the known method for automatically detecting narrow-band signals, an analog signal is received, digitized, for which the operations of sampling, quantization and coding are performed sequentially, the signal parameters are calculated, they are evaluated and the decision on the fact of signal detection is made based on the evaluation results. The digitized signal is preliminarily divided into an equal number of fragments, the samples of the fragments are inverted, the numbers of which are determined by a predefined vector of digital sequence (VCP), after which a total sample is formed, for which the samples of all fragments are summed so that the first samples of all fragments are added at the beginning, then the second and last - the last, then calculate the value of the threshold noise level, which is chosen as the value equal to twice the standard deviation samples of the total sample, and evaluate the signal parameters by comparing them with the value of the threshold noise level, moreover, the maximum negative and positive values of the total sample are selected as the signal parameters, and the decision to detect the signal is made according to the evaluation results, when at least one of the parameters by absolute value will exceed the threshold noise level. The duration of the fragments during the formation of the total sample is determined equal to the duration of the fragments, which is selected when transmitting signals. The numbers of fragments whose readings are inverted during the formation of the total sample are determined by a pre-determined IDC, on the basis of which fragments are generated during the transmission of signals, and the values of the IDC equal to zero correspond to fragments whose readout values during inversion completely coincide with the values of the sample readings corresponding to the values TCP equal to one. The length of the IDC is 4-100 values of zeros and ones located one after the other in any way, and one IDC determines the value of one bit of a logical zero or one, and the VTs that determines a logical zero differs by at least one value in the order of zeros and ones from The VCP defining the logical unit.

Thanks to a new set of essential features, the scope of the detection method for COSN in high-intensity additive noise is expanded due to an increase in the absolute value of the amplitude values of the total sample formed as a result of summation of the fragments.

The claimed method is illustrated by drawings, which show:

figure 1 is an example of a predefined VCP;

figure 2 is a sample of an analog signal, consisting of four fragments containing COSN, and within each of the fragments COSN reports are generated in accordance with the values of the predefined VCP presented in Fig.1;

figure 3 - discrete samples of the sampling of the analog signal shown in figure 2, divided into four fragments, the number of fragments corresponds to the number of elements of a predefined VCP;

figure 4 - discrete samples of the sample of the analog signal shown in figure 2, in which the reports of the fragments are inverted, the sequence numbers of which correspond to the positions of zeros in a predetermined VCP;

figure 5 - the principle of the formation of the total sample of four fragments (samples of fragments, the sequence numbers of which correspond to the positions of zeros in a predetermined VCP, inverted);

6 - the principle of the formation of the total sample of four fragments (samples of fragments, the sequence numbers of which correspond to the positions of zeros in a predetermined VCP, were not inverted).

The implementation of the claimed method is explained as follows.

1. Pre-set the VCP, according to which the values of the reports of fragments containing COSN, which must be inverted at the reception, are determined. As an example, figure 1 presents a predefined VCP consisting of zeros and ones. The total number of zeros and units of the VCP must match the number of fragments (the number of COSN) contained in the sample of the received analog signal. COSNs have two phase positions [see Kalinin V.O., Nosov V.I. Estimation of parameters of a short-pulse ultra-wideband communication system. Vestnik SibGUTI, 2011. No. 3, pp. 73-85], therefore, fragments corresponding to single values of a digital sequence are assigned COSN with one phase position, and fragments corresponding to zero values are assigned a different phase position. Figure 2 shows four fragments containing COSN. The phase positions of the signals of the first and third fragments correspond to a single value of the IDC, and the second and fourth to a zero value. The length of the VCP is from 4 to 100 values of zeros and ones, located one after another in any way. One WCP determines the value of one bit of a logical zero or one. Moreover, the VCP defining the logical zero differs by at least one value in the order of zeros and ones from the VCP defining the logical one.

2. Then take a sample of the analog signal z (t). The operation of receiving analog signals without a carrier is known and described, for example, in [Shakhnovich. I. Ultra-wideband communications. Second birth? - ELECTRONICS: Science, Technology, Business, 2001, No. 4, S.8-15]. As an example, figure 2 shows a received sample of an analog signal containing four COSN.

3. After that, the received analog signal z (t) is digitized, for which the operations of sampling, quantization, coding are sequentially performed. These operations are known, and are described, for example, in the method for automatically detecting narrowband signals according to RF patent No. 2382495 of 02/20/2010. As an example, Fig. 3 shows discrete samples z _{i of the} sample of the analog signal z (t) (see Fig. 2).

4. The sample of the digitized signal z _{i is} preliminarily divided into an equal number of fragments so that the durations of all fragments are equal to each other and within each fragment there is only one COSN. The operation of dividing by an equal number of fragments can be implemented by counting discrete samples of the digitized signal z _i . Figure 3 shows an example of dividing the digitized sample, presented in the form of discrete samples z _i , into four fragments, in accordance with the number of the IDC values (see figure 1).

5. After that, the samples of the fragments are inverted, the numbers of which are determined by the pre-determined VCP. The inversion operation can be realized by multiplying the corresponding discrete samples z _i by a coefficient equal to minus one. The operations of multiplying signals by desired coefficients are known [see The reference book of the amateur radio designer / A.A. Bokunyaev, N.M. Borisov, R.G. Varlamov et al .; Ed. N.I. Chistyakova. - M .: Radio and communications, 1990. p.31]. As an example, figure 4 shows the digitized signal, presented in the form of discrete samples z _i , in which the samples of the second and fourth fragments are inverted.

6. Then, a total sample is formed, for which the samples of all fragments are summed up so that at the beginning the first samples of all fragments are added, then the second and at the end - the last. The summation operation can be implemented based on summing devices. Adder circuits are known [see W. Titze, K. Shenk "semiconductor circuitry" M .: Mir, 1982, p.329-331]. As an example, figure 5 shows the principle of forming the total sample z0 _i obtained by adding four fragments z1 _i , z2 _i , z3 _i , z4 _i . Moreover, the first sample of the total sample z0 represents the result of the summation of the first samples, respectively, of fragments z1 _i , z2 _i , z3 _i , z4 _i . The second sample is, respectively, the result of summing the second samples, etc.

7. Then, the value of the threshold noise level is calculated, for which a value equal to twice the mean square deviation of the samples of the total sample G is selected - for positive values of samples and (-G) - for negative values of samples

Here M is the number of time samples of the processed sample signal z _i ; z _cp - the average value of the processed sample signal z _i , which is calculated by the formula

The choice of the value of the threshold noise level according to formula (1) will provide with a probability of 0.98 the fact that the amplitude values of the noise will not exceed the values of G and -G [see Borovikov V. STATISTICA. The art of data analysis on a computer: For professionals / V. Borovikov - St. Petersburg: Peter, 2003. - 688 p.]. As an example, FIG. 5 shows the levels corresponding to the values of G and -G calculated according to the formula (1).

8. The decision to detect a signal is made according to the results of the assessment when at least one of the parameters in absolute value exceeds the value of the threshold noise level. As the parameters of the digitized signal, its maximum negative D11 = min (z0 _i ) and positive D12 = max (z0 _i ) values are selected. To decide whether to detect a signal, the values of D11 = min (z0 _i ) and D12 = max (z0 _i ) are compared with the values of G and -G. A positive decision on detection is made if at least one of the following conditions is met:

The operations of selecting the maximum negative and positive values can be realized by comparing the values of z0 _{i with} each other. As an example, figure 5 shows the parameters of the signal z0 _i .

In the case when the numbers of the fragments whose readings are inverted during the formation of the total sample are determined not according to the pre-determined DCP, on the basis of which the fragments are generated during the transmission of signals, the values of the samples of the total sample z0 _i will not be accumulated. And moreover, their total value may generally be equal to zero. As an example, figure 6 shows the principle of forming the total sample when the inversion of the second and fourth fragments was not carried out. As a result, the total sample contains only zero values.

The length of the IDC is 4-100 and is selected from the conditions for ensuring the required signal-to-noise ratio (SNR) at the receiver input. The larger the number of fragments containing COSN is summed in the total sample z0 _i , the greater the SNR value at the receiver input is provided.

One WCP determines the value of one bit of a logical zero or one. The higher the number of differences in the IDC defining a bit of logical zero or one, the higher the likelihood of their correct differences at the input of the receiver.

The experiment confirmed the legitimacy of the choice of the threshold value of the noise level calculated according to the formula (1). The experiment was carried out in accordance with the requirements for obtaining statistical estimates [G. Korn, T. Korn. Math reference. Per. from English - M .: Nauka, 1977. p. 638-643].

Thus, thanks to a new set of essential features, it is possible to detect CWS in high-intensity additive noises due to an increase in the absolute value of the amplitude values of the total sample formed as a result of summing the fragments, which indicates the expansion of the scope of the claimed method and can be used in short-pulse UWB communication systems using biphasic manipulation.

Claims (3)

1. A method of detecting signals without a carrier, which consists in receiving an analog signal, digitizing it, for which the operations of sampling, quantization and coding are sequentially performed, evaluated and, based on the evaluation results, decide on the fact of signal detection, characterized in that the digitized signal is divided the fragments corresponding to the number of elements of a predefined vector of a digital sequence (VCP) invert the samples of fragments whose numbers are determined by a predefined VCP, consisting of N zero and unit values, moreover, the values of the IDC equal to zero correspond to fragments whose sample values during inversion completely coincide with the values of the samples of the fragments corresponding to the values of the IDC equal to one, after which they form a total sample, for which the samples of all the fragments are summed up so that at the beginning they add up the first samples of all fragments, then the second and at the end - the last, then calculate the value of the threshold noise level, for which a value equal to twice the value of the standard deviation of the samples of the total sample for positive and negative values of the samples, and evaluate the signal parameters by comparing them with the threshold noise level, and the maximum negative and positive values of the total sample are selected as signal parameters, and the decision to detect the signal is made according to the evaluation results, when at least one of the parameters in absolute value exceeds the value of the threshold noise level. 2. The method according to claim 1, characterized in that the duration of the fragments during the formation of the total sample is determined equal to the duration of the fragments, which is selected when transmitting signals. 3. The method according to claim 1, characterized in that the length of the VCP is 4-100 values of zeros and ones located one after another in any way, and one VTS determines the value of one bit of a logical zero or one, and the VTS that determines the logical zero is different at least one value in the order of zeros and ones from the VTSP, which determines the logical unit.

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