Method for selecting target echo signals under response-pulse interference in single-position radar detection and target designation stations using additional filter processing
The method enhances radar interference protection by using orthogonal frequency filters to distinguish target signals from interference, improving detection accuracy and reducing reliance on prior information.
Patent Information
- Authority / Receiving Office
- RU · RU
- Patent Type
- Patents
- Current Assignee / Owner
- FEDERALNOE GOSUDARSTVENNOE KAZENNOE VOENNOE OBRAZOVATELNOE UCHREZHDENIE VYSSHEGO OBRAZOVANIIA IAROSLAVSKOE VYSSHEE VOENNOE UCHILISHCHE PROTIVOVOZDUSHNOI OBORONY IMENI MARSHALA SOVETSKOGO SOIUZA L A GOVOROVA MINISTERSTVA OBORONY ROSSIISKOI FEDERATSII (RU)
- Filing Date
- 2025-11-11
- Publication Date
- 2026-06-30
AI Technical Summary
Existing methods for protecting single-position radars from response-pulse interference (RPI) are ineffective due to the need for multiple radars, inability to distinguish between false and real targets, reliance on amplitude differences that can be replicated by jamming signals, and requirement for a priori information about electromagnetic conditions.
A method using additional filter processing with matched and orthogonal frequency filters to process radar signals, forming envelope responses, determining the moment of maximum envelope, and applying the Neyman-Pearson criterion for threshold processing to distinguish between target and interference signals.
Increases the probability of correctly selecting target signals from interference with a gain of 44% at a signal-to-noise ratio of 14 dB or more, eliminating the need for a priori information about electromagnetic conditions.
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Abstract
Description
[0001] The invention relates to the field of radar and can be used in single-position radar detection and target designation stations (SDTDS) using pulsed probing signals to solve the problem of selecting targets against the background of response-pulse interference (RPI) acting along the main lobe of the antenna radiation pattern.
[0002] One effective method of electronic countermeasures against surveillance radars is the use of electronic countermeasures (ICM). A common method of creating such interference is to transmit a powerful interference signal or a series of interference signals by the jammer in response to the radar's probing signal, repeating the time-frequency structure of the radar's probing signal [1, p. 150]. For radars, such interference serves as a source of false targets. To simulate targets at different ranges, the interference signals are emitted with appropriate delay times and modulations. When massive IIM deployments occur, the radar information processing system is overloaded with false data, increasing the volume of false information provided to the user. To protect against this type of interference, it is necessary to select between radar signals reflected from the IIM signals.
[0003] A method of selection using two or more spaced radars is known [2, pp. 390-391, Fig. 10.5]. The essence of the method is that several radars perform space probing by moving the beams of antenna patterns along angular coordinates and form bursts (packets) of detected signals, using which they determine the coordinates of target marks. The coordinates of the real target will be the same for all radars. Marks from synchronous response interference will display for each radar its own false target, located on the line of sight connecting the radar and the synchronous response interference generator. As a result of the analysis of the marks received from two or more radars, the real target and the false target created by the synchronous response interference are recognized, respectively.
[0004] The disadvantage of this method is the need to use two or more spaced radars, so this method cannot be applied to single-position radars.
[0005] A method for processing a packet of radio pulses is known, based on the weighted summation of signals [3, pp. 153-157, Fig. 3.48, 3.49]. The essence of the method is that the processing of a packet of pulses reflected from a target consists of summing the pulses with weights corresponding to the expected envelope of the packet, which, when scanning the antenna beam along angular coordinates, is determined by the shape of the resulting antenna beam for transmission and reception.
[0006] The disadvantage of this method is the impossibility of recognizing a false target formed by the OIP and a real target, since the described processing of the packet of received signals in itself does not allow for the detection of distinctive features of a false and a real target.
[0007] A known method for protecting radars from pulsed and synchronous response interference [4, p. 140; 5] consists of setting two thresholds: a primary threshold and an additional threshold that exceeds it. The primary threshold level is set based on the permissible probability of a false alarm from intrinsic noise. An additional threshold is set in each range interval. Spatial signal packets are formed from signals that exceed the primary threshold. A signal packet is considered to be formed from synchronous response interference signals if one or more signals in the packet exceed the additional threshold. Using such a signal packet, the features by which similar signal packets are detected within the radar's coverage area are determined. The likelihood ratio is the signal that has undergone the appropriate processing in the radar receiver.
[0008] A disadvantage of this anti-jamming method is that the amplitude of the signal reflected by the target is the distinguishing feature of the jamming signal from its amplitude. Counter-jamming devices can generate jamming signals of any amplitude, completely replicating the structure and energy of the signal reflected from the target. Therefore, if there are no significant differences in the amplitudes of the jamming and target signals, this method is ineffective.
[0009] A method for distinguishing between two deterministic signals is known and adopted as a prototype [6, pp. 160–167], which consists of the following:
[0010] 1. Matched filtering of the adopted implementation in filters whose impulse responses correspond to the signals to be distinguished;
[0011] 2. Integration of responses from filter outputs;
[0012] 3. Calculation of residuals (subtraction) of values from filter outputs;
[0013] 4. Threshold processing to make a decision according to the expression:
[0014]
[0015] where z is the voltage from the output of the adder with an inverse input, s0, s1 are the signals to be distinguished, C1 is the threshold value.
[0016] The disadvantages of the prototype under consideration include the need for a priori information about the signals being distinguished, which is not possible under conditions of the inhomogeneity of the propagation medium, electromagnetic and design features of the sources of secondary return radiation (targets) and the presence of radio interference, as well as the high dependence of the discrimination results on the value of the signal-to-noise ratio (Fig. 1). It should also be noted that a decrease in the correlation of the input echo signal of the target (EITS) with the impulse response of the matched filter leads to an increase in the probability of error P ош signal discrimination, which leads to a decrease in the probability of correct selection, determined by the expression:
[0017]
[0018] The technical result of the present invention is to increase the probability of correct selection of P сел and the elimination of the requirement for a priori information about the electromagnetic wave propagation environment and the design features of targets when ensuring the specified detection characteristics.
[0019] The specified technical result is achieved by the fact that in the method of selecting the ES Ts against the background of the OIP in single-position radars of the OiTsU using additional filter processing, which consists of carrying out parallel operations on filter processing by a matched filter and three filters with orthogonal frequency characteristics, forming the envelope responses of the filters, determining the moment of time of reaching the maximum of the envelope response of the matched filter and forming a strobe pulse for determining the instantaneous values of the envelope responses in filters with orthogonal frequency characteristics with subsequent summation of the obtained values, calculating the decision statistics with subsequent threshold processing according to the Neyman-Pearson criterion.
[0020] The physical essence of the proposed method is as follows:
[0021] The target echo signal (Fig. 1) is formed with the participation of the entire irradiated surface of the target and is an interference of signals reflected from bright points (BP), and is described by the expression:
[0022]
[0023] U j - the amplitude of the signal reflected from the i-th bright point;
[0024] M - number of target BT;
[0025] - imaginary unit;
[0026] ƒ0- carrier frequency;
[0027] ƒ дев - frequency deviation;
[0028] τ и - radio pulse duration;
[0029] ϕ i - the initial phase of signals reflected from bright points;
[0030] τ i - signal delay time from the i-th bright point;
[0031] ƒ Дц - Doppler frequency of the target;
[0032] t - estimated time.
[0033] The response-pulse interference (Fig. 2), repeating the time-frequency structure of the probing signal, is described by the expression:
[0034]
[0035] where U0 is the interference amplitude;
[0036] ϕ0- initial phase;
[0037] ƒ Дп - Doppler interference frequency;
[0038] t3- delay time.
[0039] The input implementation model, which includes an additive mixture of the ES C or OIP and in-channel noise, is characterized by the identity:
[0040]
[0041] where y(t) is the input implementation model;
[0042] θ is a random variable that takes the values 1 - the presence of only the ES C or 0 - the presence of only the OIP;
[0043] n0(t) - model of in-channel ngums of the radar receiving device.
[0044] The input realization y(t) is processed in the matched filter according to the expression:
[0045]
[0046] where h(t) is the impulse response of the matched filter;
[0047] z(t) is the response of the matched filter (Fig. 4).
[0048] The calculation of the response envelope of the matched filter (Fig. 5) is carried out in accordance with the expression:
[0049]
[0050] where z 2 (t) - response envelope of the matched filter
[0051] z*(t) is the complex conjugate of the filter response.
[0052] The formation of a strobe pulse at time t0, corresponding to the maximum of the voltage envelope from the output of the matched filter, is carried out in accordance with the expression:
[0053]
[0054] where δ(t0) is the delta function formed at time t0.
[0055] To identify signals (to determine whether they belong to one of the two types under consideration), we modify the processing procedure used in signal discrimination theory. We take into account the characteristic feature of signals that are orthogonal in the amplified sense, which is as follows: if a pulsed signal s0(t) of duration τ is applied to the input of a filter tuned to signal s1(t) u , then the value of the voltage envelope at its output at the moment t=τ u equals zero [7, pp. 173-182].
[0056] Most often, to obtain integral recognition features, orthogonal expansions of Fourier, Karhunen-Loeve, Walsh, Haar, etc. are used [8, p. 47].
[0057] When a signal in the form of an additive sum of the expected signal from a target of one of two types and the noise of the receiving device is received at the input of the processing device containing filters with orthogonal amplitude-frequency characteristics (AFC) (Fig. 3), voltages will be generated at its outputs, proportional to the energies of the orthogonal components of the input signal, caused by the interference of signals when they are reflected from the located objects, which is calculated in accordance with the expressions:
[0058] where i is the number of the additional channel filter, which takes values 1, 2 and 3;
[0059] h i (t) impulse response of the i-th filter with orthogonal frequency characteristics;
[0060] z i (t) is the response of the i-th filter (Fig. 6);
[0061] z i 2 (t) - response envelope of the 1st filter (Fig. 7).
[0062] The estimation of instantaneous orthogonal values of the envelope voltages from the outputs of filters having orthogonal frequency characteristics, according to the gating pulse, is proportional to the energy of the complex signal from the target (with M elements poorly resolved in range) (Fig. 8b-g), and is determined in accordance with the expression:
[0063]
[0064] where - instantaneous value of the response envelope of a filter with orthogonal frequency characteristics at time t0.
[0065] The selecting feature is the sum of the responses of filters with orthogonal frequency characteristics at the moment of time corresponding to the maximum of the envelope response from the output of the matched filter and is determined by the expression:
[0066]
[0067] where - tension of the selection trait.
[0068] Calculation of the decision statistics (Fig. 11) and threshold processing according to the Neyman-Pearson criterion is carried out according to the formula:
[0069]
[0070] where h0 is the threshold value;
[0071] H1 - decision on the presence of a useful signal;
[0072] H0 - decision on the absence of a useful signal (interference signal).
[0073] Next, a decision is made about the presence or absence of a useful signal in the input implementation.
[0074] The invention is explained by the drawings presented in Fig. 1...12.
[0075] Fig. 1 shows the model of the ES Ts S Ц (t).
[0076] Fig. 2 shows the OIP S model ОИП (t)
[0077] Fig. 3a shows the frequency response of a filter matched to a probing signal.
[0078] Fig. 3b - 3g show the frequency response curves of filters with orthogonal frequency responses.
[0079] Fig. 4 shows the responses from the output of the matched filter to the ES C (solid line) and the OIP (dash-dotted line) z(t).
[0080] Fig. 5 shows the response envelopes from the output of the matched filter on the ES Ts (solid line) and the OIP (dash-dotted line) z 2 (t).
[0081] Fig. 6a - 6b show the responses from the outputs of filters with orthogonal frequency characteristics on the ES C (solid line) and the OIP (dash-dotted line) z i (t).
[0082] Fig. 7 shows the response envelopes from the outputs of filters with orthogonal frequency characteristics on the ES C (solid line) and the OIP (dash-dotted line)
[0083] Fig. 8a shows the response envelope of the matched filter in the vicinity of the maximum, corresponding to time t0, when receiving the ES C.
[0084] Fig. 8b - 8g show the response envelopes of filters with orthogonal frequency characteristics in the vicinity of time t0, when receiving the ES C.
[0085] Fig. 9a shows the response envelope of the matched filter in the vicinity of the maximum, corresponding to time t0, when receiving the OIP.
[0086] Fig. 9b - 9g show the response envelopes of filters with orthogonal frequency characteristics in the vicinity of time t0, when receiving the OIP.
[0087] Fig. 10 shows a block diagram of the device for selecting (distinguishing) the ES C and the OIP.
[0088] Fig. 11 shows the distribution densities of the stress values of the selection feature when receiving electronic communications and OIPs with a signal-to-noise ratio (SNR) q = 14 dB.
[0089] Fig. 12 shows the results of numerical simulation characterizing the SNR at the output of the processing device from the probability of selection of the ES C against the background of the developed method (solid line) and the prototype method (dash-dotted line).
[0090] The following notations are adopted.
[0091] 10.1 Matched filter.
[0092] 10.2. - 10.4 Filters with orthogonal frequency responses.
[0093] 10.5. Quadrature envelope detector.
[0094] 10.6. Maximum selection block.
[0095] 10.7. Key (strobe device).
[0096] 10.8. Adder.
[0097] 10.9. Threshold device.
[0098] The implementation of the method for selecting the EC C against the background of the OIP in single-position OIC radars using additional filter processing is possible on the basis of the detector block diagram shown in Fig. 10, and consists of the sequential execution of the following operations:
[0099] 1. The matched filter (10.1) calculates z(t) according to expression 5;
[0100] 2. The quadrature detector (10.5) forms the z envelope 2 (t) in accordance with expression 6;
[0101] 3. The maximum selection block (10.6) determines the time moment t0 and generates a strobe pulse δ(t0) in accordance with expression 7;
[0102] 4. Orthogonal frequency response filters (10.2 - 10.4) calculate z i(t) in accordance with expression 8;
[0103] 5. The quadrature detector (10.5) forms the z envelope i 2 (t) in accordance with expression 9;
[0104] 6. The key (10.7) at time t0 selects instantaneous values according to expression 10;
[0105] 7. The adder (10.8) calculates the selection feature in accordance with expression 11;
[0106] 8. Threshold device (10.9) compares the value with the threshold h0i makes a decision about the presence of the ES C in the receiving path in accordance with expression 12.
[0107] Thus, the proposed method differs from the prototype method in that filter processing is performed in filters that have orthogonal frequency characteristics, an estimate of the instantaneous values of the envelope responses of these filters and their summation, which allows, unlike the prototype, to estimate the distribution of energy across orthogonal channels.
[0108] The declared technical result is confirmed by numerical experiment.
[0109] The simulation was carried out with the following initial data: carrier frequency ƒ0= 3 GHz, frequency deviation ƒ дев = 5 MHz, pulse duration τ и = 40 μs, false alarm probability ƒ лт = 10 -4 , the probability of correct detection D0 = 0.9, the linear dimensions of the target in the azimuthal plane are 15x18 m, the range to the target / jammer is 70 km, the fluctuation of the bright dots relative to the phase center varies from 0.1 to 0.5 m, the effective scattering surface of the target σ = 1 m 2 , the number of true targets at the input of the receiving device is 1000, the number of false targets at the input of the receiving device is 1000, SNR q = 0 … 35 dB.
[0110] For the initial data considered above, an assessment was made of the efficiency of the selection of the EC C against the background of the OIP in single-position OIC radars, which is determined by the achieved probability of the correct selection of the EC C against the background of the OIP from the SNR at the input of the receiving module.
[0111] Fig. 12 shows the calculated curve characterizing the dependence of the probability of correct selection of the ESC against the background of the OIP on the SNR at the input for different methods.
[0112] Analysis of the simulation results for the above initial data showed that:
[0113] The method for selecting the EC Ts against the background of the OIP in single-position OIC radars using additional filter processing makes it possible to distinguish the EC Ts from the OIP with a probability of 0.95 at an SNR of q = 14 dB or more, providing a gain in the implemented value of 44%.
[0114] Thus, based on the above estimates, it can be concluded that the implementation of the developed method in single-position OIC radars will increase the probability of correct selection of Rсел (R сел = 0.95 at SNR q = 14 dB or more) and eliminate the requirements for a priori information about the electromagnetic wave propagation environment and the design features of targets while ensuring the specified detection characteristics.
[0115] Bibliography
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[0119] 4. Radio interference protection [Text] / M.V. Maksimov, M.P. Bobnev, B.Kh. Krivitsky et al., ed. M.V. Maksimova. - M.: Sov. radio, 1976.
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Claims
A method for selecting target echo signals against a background of response-pulse interference in single-position radar stations for detection and target designation using additional filter processing, which consists in carrying out filter processing of the received signal in a matched filter of the main channel, calculating the response envelope of the matched filter in a quadrature envelope detector, characterized in that in the maximum selection unit a strobe pulse is formed at a time corresponding to the maximum of the response envelope of the matched filter, in parallel, additional filter processing of the received signal is carried out in an additional channel having three filters with orthogonal frequency characteristics, the response envelopes of the filters of the additional channel are calculated in quadrature envelope detectors, and the instantaneous values of the response envelopes of the filters of the additional channel are estimated based on the said strobe pulse,The sum of the obtained estimates of the instantaneous values of the envelope responses of the filters of the additional channel is calculated, the calculated sum is compared with the detection threshold, which is set according to the level of the intrinsic noise of the receiving path in accordance with the specified level of false alarm, and if the sum exceeds the detection threshold, a decision is made about the presence of an echo signal of the target, and if the sum is below the threshold, a decision is made about the impact of response-pulse interference.