Delay Doppler double-extension target echo detection method and system

Abstract

The invention provides a time delay Doppler double-extension target echo detection method and system. The method comprises the following steps: estimating time delay extension information and Doppler velocity extension information of a target echo; the number of integration times and the number of waveform copy segments of the SRCI detector are calculated; calculating SRCI detector test statistics of each time delay point; acquiring a detection threshold of the SRCI detector; and comparing the SRCI detection threshold with the SRCI integral value of each time delay point, if the SRCI integral value is greater than or equal to the SRCI detection threshold, determining that the time delay point echo is a target echo, otherwise, determining that the time delay point echo is background reverberation or noise. The method has the advantages that time delay and Doppler double extension factors are fully considered, the influence of time delay or Doppler extension on the detector is reduced, and the time delay and Doppler double extension channel target echo detection performance is fully improved.

Description

Technical Field

[0001] The present application belongs to the field of sonar or radar target detection, and specifically relates to a delay Doppler double-extended target echo detection method and system. Background Art

[0002] For distortion channels such as delay spread and Doppler spread, existing detectors include RCI (Replica Correlation Integral) detector and SRC (Segmented Replica Correlation) detector. RCI detector is designed for time spread channels, while SRC detector is designed for Doppler spread channels. However, channels in actual complex environments are often delay and Doppler dual-extended channels. For delay and Doppler dual-extended channels, since the RCI detector only considers the time spread factor and the SRC detector only considers the Doppler spread factor, neither a single RCI detector nor a single SRC detector can fully improve the target echo detection performance of the delay and Doppler dual-extended channels.

[0003] When designing the detector, how to fully consider the factors of delay and Doppler double expansion and reduce the impact of delay and Doppler double expansion is crucial to improving the performance of target echo detection in multi-path and Doppler double expansion channels. Summary of the invention

[0004] The purpose of this application is to overcome the defect that the prior art cannot take into account both the delay and Doppler expansion factors.

[0005] In order to achieve the above object, the present application proposes a delay Doppler double extended target echo detection method, comprising:

[0006] Step 1: Estimate the delay spread information T of the target echo s and Doppler velocity expansion information F d ;

[0007] Step 2: Calculate the number of integrations K and the number of waveform replica segments M of the SRCI detector based on the time resolution ΔT and Doppler frequency resolution ΔF of the transmitted waveform;

[0008] Step 3: Calculate the SRCI detector test statistic for each delay point according to the number of integration times K, the number of segments M and the SRCI detector test statistic formula;

[0009] Step 4: Obtain the detection threshold of the SRCI detector according to the preset false alarm rate of the SRCI detector and the relationship formula between the false alarm rate of the SRCI detector and the detection threshold;

[0010] Step 5: Compare the SRCI detection threshold and the SRCI integral value of each time delay point. If the SRCI integral value is greater than or equal to the SRCI detection threshold, the echo at this time delay point is the target echo, otherwise it is background reverberation or noise.

[0011] As an improvement of the above method, the delay spread information T of the target echo s and Doppler velocity expansion information F d The estimation methods include:

[0012] Estimate T based on the predicted ocean environment and target characteristics information s and F d ;

[0013] The ocean environment and target characteristic information includes: ocean depth, target type, target distance and target speed.

[0014] As an improvement of the above method, the delay spread information T of the target echo s and Doppler velocity expansion information F d The estimation methods include:

[0015] Estimate or correct T in real time based on sonar data s and F d .

[0016] As an improvement of the above method, the method for calculating the number of integration times K of the SRCI detector and the number of waveform replica segments M is:

[0017] K=T s / ΔT

[0018] M=F d / ΔF.

[0019] As an improvement of the above method, the calculation method of the SRCI detector test statistic includes:

[0020]

[0021] Where y(n) represents the test statistic of the SRCI detector; N represents the number of sampling points in a signal cycle; s(·) represents the sonar transmitted signal; * represents the complex conjugate; and r(·) represents the sonar receiver received signal.

[0022] As an improvement of the above method, the relationship between the false alarm rate and the detection threshold of the SRCI detector is as follows:

[0023]

[0024] Wherein, PFA represents the false alarm rate PFA of the SRCI detector; Th represents the detection threshold.

[0025] The present application also provides a delay Doppler double extended target echo detection system, which is implemented based on the above method, and the system includes:

[0026] The estimated parameter module is used to estimate the delay spread information T of the target echo. s and Doppler velocity expansion information F d ;

[0027] The module for calculating the number of integrations and the number of segments is used to calculate the number of integrations K and the number of segments M of the waveform replicas of the SRCI detector according to the time resolution ΔT and the Doppler frequency resolution ΔF of the transmitted waveform;

[0028] The module for calculating the test statistic of the SRCI detector is used to calculate the test statistic of the SRCI detector at each delay point according to the number of integration times K, the number of segments M and the test statistic formula of the SRCI detector;

[0029] The module for obtaining the detection threshold of the SRCI detector is used to obtain the detection threshold of the SRCI detector according to the preset false alarm rate of the SRCI detector and the relationship formula between the false alarm rate of the SRCI detector and the detection threshold;

[0030] The target echo judgment module is used to compare the SRCI detection threshold and the SRCI integral value of each time delay point. If the SRCI integral value is greater than or equal to the SRCI detection threshold, the echo at this time delay point is the target echo, otherwise it is background reverberation or noise.

[0031] Compared with the prior art, the advantages of this application are:

[0032] The time delay and Doppler dual expansion factors are fully considered, the influence of time delay or Doppler expansion on the detector is reduced, and the target echo detection performance of the time delay and Doppler dual expansion channel is fully improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The figure shows a flow chart of a delay Doppler double extended target echo detection method;

[0034] Figure 2(a) shows the correlation peak detection result of the dual extended echo RC detector;

[0035] Figure 2(b) shows the correlation peak detection result of the dual extended echo RCI detector;

[0036] Figure 2(c) shows the correlation peak detection result of the dual extended echo SRC detector;

[0037] Figure 2(d) shows the correlation peak detection result of the dual extended echo SRCI detector. DETAILED DESCRIPTION

[0038] The technical solution of the present application is described in detail below with reference to the accompanying drawings.

[0039] In order to solve the problem that existing RCI, SRC and other detectors do not fully consider the delay and Doppler double extension factors and have poor detection performance under the conditions of delay and Doppler double extension channels, the present invention invents a segmented replica correlation integral (SRCI) detector. The SRCI detector fully considers the delay and Doppler double extension factors of the target echo channel, effectively reduces the influence of the delay and Doppler double extension on the target echo detection, and improves the delay and Doppler double extension channel target echo detection performance.

[0040] Example 1

[0041] The present invention proposes a segmented replica correlation integral (SRCI) detector based on the existing segmented replica correlation (SRC) detector and replica correlation integral (RCI) detector, and proposes a delay Doppler double extended target echo detection method using the detector, such as Figure 1 As shown, the method includes:

[0042] Step 1: Estimate the delay spread information T of the target echo s and Doppler velocity expansion information F d ; Target echo T s and F d It can be roughly estimated based on the predicted ocean environment and target characteristics (such as sea depth, target type, target distance, target speed, etc.), or it can be estimated or corrected in real time based on sonar data. s and F d ;

[0043] Step 2: After estimating T s and F d Then, according to the time resolution ΔT and Doppler frequency resolution ΔF of the transmitted waveform, the number of integration times K of the SRCI detector and the number of waveform replica segments M are calculated, where K = T s / ΔT,M=F d / ΔF;

[0044] Step 3: Calculate the SRCI detector test statistic value for each delay point according to the number of integration times K, the number of segments M and the SRCI detector test statistic formula. The SRCI detector test statistic formula is shown in formula (7);

[0045] Step 4: According to the preset SRCI detector false alarm rate and the relationship formula between the SRCI detector false alarm rate and the detection threshold, the SRCI detector detection threshold is obtained. The relationship formula between the SRCI detector false alarm rate and the detection threshold is shown in formula (8);

[0046] Step 5: Compare the SRCI detection threshold and the SRCI integral value of each time delay point. If the SRCI integral value is greater than or equal to the SRCI detection threshold, the echo at this time delay point is the target echo, otherwise it is background reverberation or noise.

[0047] The following is a theoretical introduction to the detector using sonar signals as an example.

[0048] Assume that the sonar transmission signal is s(t), its bandwidth is B, pulse width is T, the target echo signal is x(t), the channel background noise (or reverberation) is v(t), and the sonar receiver receives the signal r(t), then r(t) can be expressed as:

[0049]

[0050] Where, t is the continuous time;

[0051] For an ideal channel single bright spot target echo, the discrete received signal can be expressed as:

[0052]

[0053] Where i is the discrete time; A is the single bright spot target echo channel amplitude factor, is a random phase jump uniformly distributed in [0,2π], τ is the round-trip delay of a single bright spot target echo, and f s is the signal sampling rate, and N represents the number of sampling points in one signal period.

[0054] Under the background of complex Gaussian white noise, the best likelihood ratio receiver filter for the single bright spot target echo in an ideal channel is a matched filter, also known as a replica correlation (RC) detector, whose output is the convolution of the received signal data and the replica of the transmitted signal. The test statistic of the RC detector is:

[0055]

[0056] Where * represents complex conjugate. When there is only noise v(t), assuming the noise power is 1, that is, E(v(n) 2 )=1, then z(n) is a cyclic complex Gaussian random variable, that is, z(n)~N(0,2), the real part and imaginary part of z(n) are independent and both obey N(0,1), and their square sum y(n) obeys the central χ with 2 degrees of freedom 2 Distribution, that is, y(n)~χ 2 (2). At this time, the false alarm rate PFA of the RC detector is:

[0057]

[0058] Wherein, Th is the detection threshold when the false alarm rate of the RC detector is not greater than PFA.

[0059] The replica correlation integration (RCI) detector can be expressed as the maximum likelihood ratio test statistic of the ideal channel target echo from 0 to the extended time T s The points on .

[0060] The RCI detector test statistic is shown in formula (5).

[0061]

[0062] Where K is the number of integrations.

[0063] The Segmented Replica Correlation (SRC) detector divides the replica waveform into M equal segments to correlate with the received echo and sums the square of the amplitude of each correlation. The SRC detector test statistic is shown in formula (6).

[0064]

[0065] Where M is the number of replica waveform segments.

[0066] For the delay-Doppler double-extended channel echo, we propose a segmented replica correlation integration (SRCI) detector. The test statistic of the SRCI detector is shown in formula (7).

[0067]

[0068] When there is only noise v(t), the noise power is assumed to be 1, that is, E(v(n) 2 )=1, then {z km (n), k = 0, 1, 2···K-1, m = 0, 1, 2···M-1} is a cyclic complex Gaussian random variable, that is, z km (n)~N(0,2), z km (n) The real and imaginary parts are independent and both obey N(0,1). Their square sum y(n) obeys the central χ with 2KM degrees of freedom. 2 Distribution, that is, y(n)~χ 2 (2KM). At this time, the false alarm rate PFA of the SRCI detector is:

[0069]

[0070] In the formula, Γ(·) is the Gamma function, Th is the detection threshold when the false alarm rate of the SRCI detector is not greater than PFA, K is the number of integrations, and M is the number of replica waveform segments. Based on formula (8), the detection threshold Th of the SRCI detector with K integrations and M segments under different false alarm rates PFA can be obtained.

[0071] Depend on Figure 2(a)-Figure 2(d) It can be seen that the RC detector correlation peak is about 0.22×10 ^21 , the RCI detector correlation peak is about 0.8×10 ^21 , the SRC detector correlation peak is about 1.2×10 ^21 , while the correlation peak of the SRCI detector proposed in the present invention is about 3.3×10 ^21 , compared with RC, RCI and SRC detectors, the correlation peaks are significantly increased.

[0072] Example 2

[0073] The present application also provides a delay Doppler double extended target echo detection system, which is implemented based on the above method, and the system includes:

[0074] The estimated parameter module is used to estimate the delay spread information T of the target echo. s and Doppler velocity expansion information F d ;

[0075] The module for calculating the number of integrations and the number of segments is used to calculate the number of integrations K and the number of segments M of the waveform replicas of the SRCI detector according to the time resolution ΔT and the Doppler frequency resolution ΔF of the transmitted waveform;

[0076] The module for calculating the test statistic of the SRCI detector is used to calculate the test statistic of the SRCI detector at each delay point according to the number of integration times K, the number of segments M and the test statistic formula of the SRCI detector;

[0077] The module for obtaining the detection threshold of the SRCI detector is used to obtain the detection threshold of the SRCI detector according to the preset false alarm rate of the SRCI detector and the relationship formula between the false alarm rate of the SRCI detector and the detection threshold;

[0078] The target echo judgment module is used to compare the SRCI detection threshold and the SRCI integral value of each time delay point. If the SRCI integral value is greater than or equal to the SRCI detection threshold, the echo at this time delay point is the target echo, otherwise it is background reverberation or noise.

[0079] The present application may also provide a computer device, comprising: at least one processor, a memory, at least one network interface and a user interface. The various components in the device are coupled together through a bus system. It is understood that the bus system is used to achieve connection and communication between these components. In addition to the data bus, the bus system also includes a power bus, a control bus and a status signal bus.

[0080] The user interface may include a display, a keyboard or a pointing device, such as a mouse, a trackball, a touch pad or a touch screen.

[0081] It is understood that the memory in the embodiments disclosed in the present application may be a volatile memory or a non-volatile memory, or may include both volatile and non-volatile memories. Among them, the non-volatile memory may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory may be a random access memory (RAM), which is used as an external cache. By way of example and not limitation, many forms of RAM are available, such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDRSDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous link dynamic random access memory (SLDRAM), and direct memory bus random access memory (DRRAM). The memories described herein are intended to include, but are not limited to, these and any other suitable types of memories.

[0082] In some embodiments, the memory stores the following elements, executable modules or data structures, or a subset thereof, or an extended set thereof: an operating system and applications.

[0083] The operating system includes various system programs, such as a framework layer, a core library layer, a driver layer, etc., which are used to implement various basic services and process hardware-based tasks. The application includes various application programs, such as a media player (Media Player), a browser (Browser), etc., which are used to implement various application services. The program for implementing the method of the embodiment of the present disclosure can be included in the application.

[0084] In the above embodiment, the processor may also call a program or instruction stored in the memory, specifically, a program or instruction stored in an application program, and is used to:

[0085] Execute the steps of the above method.

[0086] The above method can be applied to a processor or implemented by a processor. The processor may be an integrated circuit chip with signal processing capabilities. In the implementation process, each step of the above method can be completed by an integrated logic circuit of hardware in the processor or an instruction in the form of software. The above processor may be a general processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components. The above disclosed methods, steps and logic block diagrams can be implemented or executed. The general processor may be a microprocessor or the processor may also be any conventional processor, etc. The steps of the above disclosed method can be directly embodied as being executed by a hardware decoding processor, or executed by a combination of hardware and software modules in the decoding processor. The software module may be located in a mature storage medium in the field such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory or an electrically erasable programmable memory, a register, etc. The storage medium is located in a memory, and the processor reads the information in the memory and completes the steps of the above method in combination with its hardware.

[0087] It is understood that the embodiments described in the present application can be implemented by hardware, software, firmware, middleware, microcode or a combination thereof. For hardware implementation, the processing unit can be implemented in one or more application specific integrated circuits (ASIC), digital signal processors (DSP), digital signal processing devices (DSPD), programmable logic devices (PLD), field programmable gate arrays (FPGA), general-purpose processors, controllers, microcontrollers, microprocessors, other electronic units for performing the functions described in the present application or a combination thereof.

[0088] For software implementation, the technology of the present application can be implemented by executing the functional modules (such as procedures, functions, etc.) of the present application. The software code can be stored in a memory and executed by a processor. The memory can be implemented in the processor or outside the processor.

[0089] The present application may also provide a non-volatile storage medium for storing a computer program. When the computer program is executed by a processor, each step in the above method embodiment can be implemented.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present application and are not intended to limit it. Although the present application is described in detail with reference to the embodiments, a person skilled in the art should understand that any modification or equivalent replacement of the technical solution of the present application does not depart from the spirit and scope of the technical solution of the present application and should be included in the scope of the claims of the present application.

Claims

1. A delay Doppler double extended target echo detection method, comprising: Step 1: Estimate the delay spread information T of the target echo s and Doppler velocity expansion information F d ; Step 2: Calculate the number of integrations K and the number of waveform replica segments M of the SRCI detector based on the time resolution ΔT and Doppler frequency resolution ΔF of the transmitted waveform; Step 3: Calculate the SRCI detector test statistic for each delay point according to the number of integration times K, the number of segments M and the SRCI detector test statistic formula; Step 4: Obtain the detection threshold of the SRCI detector according to the preset false alarm rate of the SRCI detector and the relationship formula between the false alarm rate of the SRCI detector and the detection threshold; Step 5: Compare the SRCI detection threshold and the SRCI integral value of each time delay point. If the SRCI integral value is greater than or equal to the SRCI detection threshold, the echo at this time delay point is the target echo, otherwise it is background reverberation or noise.

2. The delay Doppler double extended target echo detection method according to claim 1, characterized in that: The delay spread information T of the target echo s and Doppler velocity expansion information F d The estimation methods include: Estimate T based on the predicted ocean environment and target characteristics information s and F d ; The ocean environment and target characteristic information includes: ocean depth, target type, target distance and target speed.

3. The delay Doppler double extended target echo detection method according to claim 1, characterized in that: The delay spread information T of the target echo s and Doppler velocity expansion information F d The estimation methods include: Estimate or correct T in real time based on sonar data s and F d .

4. The delay Doppler double extended target echo detection method according to claim 1, characterized in that: The method for calculating the number of integration times K and the number of waveform replica segments M of the SRCI detector is: K=T s / ΔT M=F d / ΔF。 5. The delay Doppler double extended target echo detection method according to claim 1, characterized in that: The calculation method of the SRCI detector test statistic includes: Where y(n) represents the test statistic of the SRCI detector; N represents the number of sampling points in a signal cycle; s(·) represents the sonar transmitted signal; * represents the complex conjugate; and r(·) represents the sonar receiver received signal.

6. The delay Doppler double extended target echo detection method according to claim 1, characterized in that: The relationship between the false alarm rate and the detection threshold of the SRCI detector is as follows: Wherein, PFA represents the false alarm rate PFA of the SRCI detector; Th represents the detection threshold.

7. A delay Doppler double extended target echo detection system, implemented based on any method described in claims 1-6, characterized in that: The system comprises: The estimated parameter module is used to estimate the delay spread information T of the target echo. s and Doppler velocity expansion information F d ; The module for calculating the number of integrations and the number of segments is used to calculate the number of integrations K and the number of segments M of the waveform replicas of the SRCI detector according to the time resolution ΔT and the Doppler frequency resolution ΔF of the transmitted waveform; The module for calculating the test statistic of the SRCI detector is used to calculate the test statistic of the SRCI detector at each delay point according to the number of integration times K, the number of segments M and the test statistic formula of the SRCI detector; A module for obtaining a detection threshold of an SRCI detector is used to obtain a detection threshold of an SRCI detector according to a preset false alarm rate of the SRCI detector and a relationship formula between the false alarm rate of the SRCI detector and the detection threshold; and The target echo judgment module is used to compare the SRCI detection threshold and the SRCI integral value of each time delay point. If the SRCI integral value is greater than or equal to the SRCI detection threshold, the echo at this time delay point is the target echo, otherwise it is background reverberation or noise.

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