A time delay doppler double spread target echo detection method and system

Abstract

The application provides a time delay Doppler double expansion target echo detection method and system, the method comprises the following steps: estimating time delay expansion information and Doppler velocity expansion information of a target echo; calculating the integral number of an SRCI detector and the number of waveform copy segments; calculating the SRCI detector test statistics of each time delay point; obtaining an SRCI detector detection threshold; comparing 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 of the time delay point is a target echo, otherwise, it is background reverberation or noise. The application has the advantages that: the time delay and Doppler double expansion factors are fully considered, the influence of time delay or Doppler expansion on the detector is reduced, and the time delay, Doppler double expansion channel target echo detection performance is fully improved.

Description

TECHNICAL FIELD

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

[0002] For time-delay extended, Doppler extended and other distorted channels, existing detectors include an RCI (replica correlation integration) detector and an SRC (segmented replica correlation) detector. The RCI detector is a detector designed for a time-extended channel, and the SRC detector is a detector designed for a Doppler-extended channel. However, a channel in an actual complex environment is often a time-delay, Doppler double-extended channel. For the time-delay, Doppler double-extended channel, since the RCI detector only considers the time-extended factor and the SRC detector only considers the Doppler-extended factor, neither the RCI detector alone nor the SRC detector alone can sufficiently improve the target echo detection performance of the time-delay, Doppler double-extended channel.

[0003] In the design of a detector, how to sufficiently consider the time-delay, Doppler double-extended factors and reduce the influence of the time-delay, Doppler double-extended factors is crucial for improving the target echo detection performance of a multi-path, Doppler double-extended channel. SUMMARY

[0004] The application aims to overcome the defect that the prior art cannot consider the time-delay, Doppler double-extended factors.

[0005] To achieve the above object, the application provides a time-delay, Doppler double-extended target echo detection method, which includes the following steps.

[0006] Step 1: estimating time-delay extended information T of a target echo s and Doppler velocity extended information F d .

[0007] Step 2: calculating the integration number K of an SRCI detector and the waveform replica segmentation number M according to the time resolution AT of a transmitted waveform and the Doppler frequency resolution AF.

[0008] Step 3: calculating the SRCI detector test statistic of each time-delay point according to the integration number K, the segmentation number M and the SRCI detector test statistic formula.

[0009] Step 4: obtaining the SRCI detector detection threshold according to a preset SRCI detector false alarm rate and an SRCI detector false alarm rate and detection threshold relationship formula.

[0010] Step 5: compare the SRCI detection threshold with the SRCI integrated value of each time delay point, if the SRCI integrated value is greater than or equal to the SRCI detection threshold, the echo of this time delay point is target echo, otherwise it is background reverberation or noise.

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

[0012] estimating T s and F d according to the known ocean environment and target characteristic information.

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

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

[0015] estimating or correcting T s and F d in real time according to the sonar collection data.

[0016] As an improvement of the above method, the method for calculating the integral times K and waveform copy segment number M of the SRCI detector comprises:

[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 comprises:

[0020]

[0021] wherein y(n) represents the SRCI detector test statistic; N represents the sampling point number of a signal period; s(·) represents the sonar transmission signal; * represents complex conjugate; r(·) represents the sonar receiver received signal.

[0022] As an improvement of the above method, the false alarm rate and detection threshold relationship formula of the SRCI detector comprises:

[0023]

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

[0025] The application also provides a time delay and Doppler double expansion target echo detection system, which is realized based on the above method and comprises:

[0026] a predicted parameter module, which is configured to predict time delay expansion information T s and Doppler velocity expansion information F d of a target echo.

[0027] a calculation module, which is configured to calculate the integral number K and waveform copy segment number M of the SRCI detector according to the time resolution AT and Doppler frequency resolution AF of a transmitted waveform.

[0028] a calculation module, which is configured to calculate the integral number K and waveform copy segment number M of the SRCI detector according to the time resolution AT and Doppler frequency resolution AF of a transmitted waveform.

[0029] a calculation module, which is configured to calculate the integral number K and waveform copy segment number M of the SRCI detector according to the time resolution AT and Doppler frequency resolution AF of a transmitted waveform.

[0030] a calculation module, which is configured to calculate the integral number K and waveform copy segment number M of the SRCI detector according to the time resolution AT and Doppler frequency resolution AF of a transmitted waveform.

[0031] Compared with the prior art, the application has the following advantages:

[0032] The time delay and Doppler double 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 double expansion channel is fully improved. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 Fig. 1 is a flow chart of a time delay and Doppler double expansion target echo detection method.

[0034] Fig. 2(a) shows the related peak detection result of a double expansion echo RC detector.

[0035] Fig. 2(b) shows the related peak detection result of a double expansion echo RCI detector.

[0036] Fig. 2(c) shows the related peak detection result of a double expansion echo SRC detector.

[0037] Fig. 2(d) shows the related peak detection result of a double expansion echo SRCI detector. DETAILED DESCRIPTION

[0038] The technical solution of this application will be described in detail below with reference to the accompanying drawings.

[0039] This invention addresses the problem that existing detectors such as RCI and SRC do not fully consider time delay and Doppler double spread factors, resulting in poor detection performance under time delay and Doppler double spread channel conditions. It proposes a segmented replica correlation integral (SRCI) detector, which fully considers the time delay and Doppler double spread factors of the target echo channel, effectively reducing the impact of time delay and Doppler double spread on target echo detection and improving the target echo detection performance under time delay and Doppler double spread channels.

[0040] Example 1

[0041] This invention proposes a segmented replica correlation integral (SRCI) detector based on existing segmented replica correlation (SRC) detectors and replica correlation integral (RCI) detectors, and utilizes this detector to propose a time-delay Doppler dual-spread target echo detection method, such as... Figure 1 As shown, the method includes:

[0042] Step 1: Estimate the time delay spread information T of the target echo. s And Doppler velocity extension information F d ; Target echo T s and F d T can be roughly estimated based on known marine 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, based on the time resolution ΔT and Doppler frequency resolution ΔF of the transmitted waveform, the integration count K and the number of waveform replica segments M of the SRCI detector are calculated, where K = T s / ΔT, M=F d / ΔF;

[0044] Step 3: Calculate the SRCI detector test statistic value for each time delay point based on the number of integrations 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: Based on the preset false alarm rate of the SRCI detector and the formula relating the false alarm rate of the SRCI detector to the detection threshold, obtain the detection threshold of the SRCI detector. The formula relating the false alarm rate of the SRCI detector to the detection threshold is shown in Formula (8).

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

[0047] The detector is theoretically introduced below taking sonar signals as an example.

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

[0049]

[0050] where t is continuous time;

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

[0052]

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

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

[0055]

[0056] where * represents complex conjugate. When there is only noise v(t), assuming the noise power is 1, i.e. E(v(n) 2 ) = 1, then z(n) is a circular complex Gaussian random variable, i.e. z(n) ~ N(0, 2), the real part and the imaginary part of z(n) are independent of each other and both subject to N(0, 1), and their square sum y(n) is subject to central χ 2 distribution with degree of freedom 2, i.e. y(n) ~ χ 2 (2). At this time, the false alarm rate PFA of the RC detector is:

[0057]

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

[0059] The Replica Correlation Integration (RCI) detector can be represented as the integration of the maximum likelihood ratio test statistic of the ideal channel target echo over the interval from 0 to the integration time T s

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

[0061]

[0062] where K is the integration number.

[0063] The Segmented Replica Correlation (SRC) detector correlates the replica waveform segmented into M equal segments with the received echo and sums the squared amplitudes of each segment correlation. The SRC detector test statistic is shown in equation (6).

[0064]

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

[0066] For the time-doppler doubly spread channel echo, we propose the Segmented Replica Correlation Integration (SRCI) detector, and the SRCI detector test statistic is shown in equation (7).

[0067]

[0068] When there is only noise v(t), assuming the noise power is 1, i.e., E(v(n) 2 ) = 1, then {z km (n), k = 0, 1, 2, ···, K-1, m = 0, 1, 2, ···, M-1} are circular complex Gaussian random variables, i.e., z km (n) ~ N(0, 2), z km (n) real and imaginary parts are independent of each other and both follow N(0, 1), and their sum of squares y(n) follows the central χ 2 distribution with 2KM degrees of freedom, i.e., 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 of the SRCI detector when the false alarm rate is not greater than that of 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 Figures 2(a)-2(d) It can be seen that the correlation peak value of the RC detector is approximately 0.22 × 10⁻⁶. ^21 The RCI detector correlation peak is approximately 0.8 × 10⁻⁶. ^21 The SRC detector correlation peak is approximately 1.2 × 10⁻⁶. ^21 The SRCI detector proposed in this invention has a correlation peak of approximately 3.3 × 10⁻⁶. ^21 The correlation peak value is significantly larger compared to that of RC, RCI and SRC detectors.

[0072] Example 2

[0073] This application also provides a time-delay Doppler dual-extended target echo detection system, implemented based on the above method, the system comprising:

[0074] The prediction parameter module is used to predict the time delay spread information T of the target echo. s And Doppler velocity extension 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 waveform replica segments M of the SRCI detector based on the time resolution ΔT and Doppler frequency resolution ΔF of the transmitted waveform.

[0076] The module for calculating the SRCI detector test statistic is used to calculate the SRCI detector test statistic for each time delay point based on the number of integrations K, the number of segments M, and the SRCI detector test statistic formula.

[0077] The module for obtaining the detection threshold of the SRCI detector is used to obtain the detection threshold of the SRCI detector based on the preset false alarm rate of the SRCI detector and the formula relating the false alarm rate of the SRCI detector to the detection threshold.

[0078] The target echo determination module compares the SRCI detection threshold with the SRCI integral value at each time delay point. If the SRCI integral value is greater than or equal to the SRCI detection threshold, then the echo at this time delay point is the target echo; otherwise, it is background reverberation or noise.

[0079] The application can 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 by a bus system. It can be understood that the bus system is used to realize the connection communication between the components. In addition to including a data bus, the bus system also includes a power supply bus, a control bus and a status signal bus.

[0080] The user interface can include a display, a keyboard or a pointing device, for example, a mouse, a trackball, a touchpad or a touch screen.

[0081] It can be understood that the memory in the embodiments of the application can be a volatile memory or a non-volatile memory, or can include both volatile and non-volatile memories. The non-volatile memory can be a Read-Only Memory (ROM), a Programmable ROM (PROM), an Erasable PROM (EPROM), an Electrically EPROM (EEPROM) or a flash memory. The volatile memory can be a Random Access Memory (RAM) used as an external cache. By way of example, but not limitation, many forms of RAM can be used, such as Static RAM (SRAM), Dynamic RAM (DRAM), Synchronous DRAM (SDRAM), Double Data Rate SDRAM (DDR SDRAM), Enhanced SDRAM (ESDRAM), Synchlink DRAM (SLDRAM) and Direct Rambus RAM (DRRAM). The memory described herein is intended to include, but not be limited to, these and any other suitable types of memory.

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

[0083] The operating system includes various system programs, such as a framework layer, a core library layer, a driver layer, and the like, for implementing various basic services and processing hardware-based tasks. The application programs include various application programs, such as a media player (Media Player), a browser (Browser), and the like, for implementing various application services. The program for implementing the method of the embodiments of the present disclosure can be included in the application programs.

[0084] In the above-described embodiments, the processor can be configured to, by invoking the program or the instruction stored in the memory, specifically, the program or the instruction stored in the application program:

[0085] perform the steps of the above-described method.

[0086] The above-described method can be applied to the processor or implemented by the processor. The processor can be an integrated circuit chip having a signal processing capability. In the implementation process, the steps of the above-described method can be completed by hardware integrated logic circuits in the processor or by the instructions in the form of software. The processor described above can be a general-purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components. The above-disclosed methods, steps and logic block diagrams can be implemented or executed by the processor. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor. The steps of the above-disclosed method can be directly embodied in hardware code executed by the processor, or a combination of hardware and software modules in the processor. The software module can be located in the random access memory (RAM), the flash memory, the read-only memory (ROM), the programmable read-only memory (PROM), the electrically programmable read-only memory (EPROM), the electrically erasable programmable read-only memory (EEPROM), the register, or other mature storage media in the art. The memory is located in the storage medium, and the processor reads information in the memory and combines the hardware to complete the steps of the above-described method.

[0087] It can be understood that the embodiments described in the present application can be realized 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 (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), general purpose processors, controllers, micro-controllers, microprocessors, other electronic units designed to perform the functions described in the present application, or a combination thereof.

[0088] For software implementation, the present application can be implemented by executing the functional modules (such as processes, functions, etc.) described in 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 can also provide a non-volatile storage medium for storing a computer program. When the computer program is executed by a processor, each step of the above method embodiments can be implemented.

[0090] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present application and not to limit. Although the present application is described in detail with reference to the embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application, and they should be covered in the scope of the claims of the present application.

Claims

1. A time delay Doppler double spread target echo detection method, comprising: Step 1: Estimate the time delay spread information T of the target echo s and Doppler velocity spread information F d ; Step 2: calculating the integration number K and the waveform copy segment number M of the SRCI detector according to the time resolution AT and the Doppler frequency resolution AF of the transmitted waveform; Step 3: calculating the SRCI detector test statistic of each time delay point according to the integration number K, the segment number M and the SRCI detector test statistic formula; Step 4: obtaining the SRCI detector detection threshold according to the preset SRCI detector false alarm rate and the SRCI detector false alarm rate and detection threshold relationship formula; Step 5: comparing the SRCI detection threshold and the SRCI integration value of each time delay point, if the SRCI integration value is greater than or equal to the SRCI detection threshold, then the echo of this time delay point is a target echo, otherwise it is background reverberation or noise; The calculation method of the SRCI detector test statistic comprises: Wherein, y(n) represents the SRCI detector test statistic; N represents the sampling point number of a signal period; s(·) represents the sonar transmitted signal; * represents complex conjugate; r(·) represents the sonar receiver received signal.

2. The time delay Doppler dual spread target echo detection method according to claim 1, characterized in that, The time delay spread information T of the target echo s And the Doppler velocity spread information F d The estimation method comprises: T is estimated from a priori knowledge of the marine environment and target characteristics information s and F d ; The marine environment and target characteristic information comprises: sea depth, target type, target distance and target speed.

3. The time delay Doppler dual spread target echo detection method of claim 1, wherein, The time delay spread information T of the target echo s and the Doppler velocity spread information F d The estimation method comprises: Real-time estimation or correction of T from sonar collected data s and F d .

4. The time delay Doppler dual spread target echo detection method of claim 1, wherein, The method for calculating the integration number K and the waveform copy segment number M of the SRCI detector is: K = T s ΔT M = F d ΔF.

5. The time delay Doppler dual spread target echo detection method of claim 1, wherein, The SRCI detector false alarm rate and detection threshold relationship formula is: Wherein, PFA represents the false alarm rate PFA of the SRCI detector; Th represents the detection threshold.

6. A time delay Doppler double spread target echo detection system, realized on the basis of the method according to any one of claims 1 to 5, characterized in that The system comprises: an estimation parameter module, configured to estimate time delay spread information T of the target echo s and Doppler velocity spread information F d ; A calculation integration number and segment number module, configured to calculate the integration number K and the waveform copy segment number M of the SRCI detector according to the time resolution AT and the Doppler frequency resolution AF of the transmitted waveform; A SRCI detector test statistic calculation module, configured to calculate the SRCI detector test statistic of each time delay point according to the integration number K, the segment number M and the SRCI detector test statistic formula; An SRCI detector detection threshold acquisition module, configured to obtain the SRCI detector detection threshold according to the preset SRCI detector false alarm rate and the SRCI detector false alarm rate and detection threshold relationship formula; and A target echo judgment module, configured to compare the SRCI detection threshold and the SRCI integration value of each time delay point, if the SRCI integration value is greater than or equal to the SRCI detection threshold, then the echo of this time delay point is a target echo, otherwise it is background reverberation or noise.

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