A multi-channel optoelectronic delay line radar extended target simulation system and method

Abstract

The invention discloses a multi-channel photoelectric delay line radar extended target simulation system and method, belonging to the field of radar simulation technology. The system comprises a radar signal receiving and echo signal transmitting module, a frequency mixing and echo Doppler frequency shift module, a multi-target echo simulation module, a delay module and an attenuation module. The method comprises the following steps: mixing a received radar signal to convert it into an intermediate frequency signal; performing multi-target echo simulation on the intermediate frequency signal to convert it into a multi-channel intermediate frequency signal; delaying and attenuating each branch signal of the multi-channel intermediate frequency signal to obtain a delayed and attenuated multi-channel intermediate frequency signal; combining the delayed and attenuated multi-channel intermediate frequency signal to generate an intermediate frequency signal carrying multi-target information; mixing and transmitting the intermediate frequency signal to load Doppler frequency shift information to obtain a simulated target echo signal, thereby completing the simulation of the target echo.

Description

Technical Field

[0001] The present invention belongs to the technical field of radar simulation, and in particular relates to a multi-channel photoelectric delay line radar extended target simulation system and method. Background Art

[0002] The testing phase is essential during radar system design and production. To reduce radar R&D costs and development cycles, enhance test confidentiality, and minimize the reliance on the actual testing environment and site, radar target simulator design has become a key technology in radar system testing. A radar target simulator primarily simulates the target's reflection echo from the radar signal. Targets smaller than the radar resolution can be treated as point targets, while complex targets much larger than the radar resolution must be treated as extended targets. According to electromagnetic theory, target scattering from an extended target is not entirely due to the contribution of the entire surface but can be fully characterized by localized scattering sources, known as scattering centers, each of which is considered isolated. The electromagnetic scattering characteristics of an extended target are the result of the combined effects of several scattering centers located on it, and its total electromagnetic scattering field is approximately the sum of the scattering fields of each scattering center. Therefore, to describe and simulate the extended target model, it is necessary to calculate the time-domain convolution of the target characteristics of each scattering point with the radar transmit signal to obtain the echo signal of a single scattering point. The echo signals from each scattering point are then summed in the time domain to obtain the echo signal of the extended target.

[0003] Currently, the most widely used radar target simulation technology is Digital Radio Frequency Memory (DRFM). Its basic workflow is as follows: First, the received signal's coarse frequency is measured, used to tune the local oscillator (LO). The RF signal and the LO signal undergo quadrature down-conversion, mixing, and filtering to generate baseband I (in-phase) and Q (quadrature) baseband signals. Analog / Digital (A / D) converters then quantize and sample the baseband I and Q signals, converting the analog signals into digital signals. The digitized I and Q signals are stored in memory and can then be convolved with target characteristic data to simulate target characteristics. Time delay processing can also be used to simulate target range. The processed baseband I and Q signals undergo quadrature up-conversion, performing Doppler frequency modulation. The same LO is used for up-conversion and down-conversion. A controller selects various DRFM operating modes to meet diverse application requirements.

[0004] Patent application number CN117269907A, filed on September 22, 2023, by Zhang Shishan, Sun Long, and Xu Xihu, proposes a high-precision continuous-wave radar target simulation method and device based on DRFM. This system requires digitizing the radar signal, then differentially calculating phase data, fitting multi-channel frequency measurement data, and calculating the radar signal's frequency modulation slope. This results in a complex circuit structure and high cost. The intermediate frequency (IF) signal processes broadband signals at a slow speed, with an instantaneous bandwidth of only 2GHz. The time required for the digital-to-analog conversion process is difficult to precisely control. The digital circuit generating the digital IF signal must wait for sufficient data to be packaged into a single block before sending it to the DAC (Digital to Analog Converter). This delay can cause the signal to span multiple cycles, reaching hundreds of nanoseconds. Because they are not in the same cycle, the coherence between the intercepted and forwarded signals is extremely poor. Furthermore, the conversion between analog and digital signals generates more noise.

[0005] On May 10, 2023, Chen Xu, Wang Jinfeng, and Zhu Ping published a paper titled "Radar target echo simulation and verification based on extended targets." [J] Ship Electronic Countermeasures, 2023, 46(05): 55-59+87. DOI: 10.16426. The DAC converter used in this system has a maximum frequency of only 2.5 GSPS, indicating that the system can only support a maximum bandwidth of 1.25 GHz. Therefore, this technology can achieve a small bandwidth. At the same time, the system core uses digital chips such as DSP (digital signal processor), FPGA (Field Programmable Gate Array), and DAC, which increases system latency and poor real-time performance. Summary of the Invention

[0006] The purpose of the present invention is to overcome the problems of narrow bandwidth and high delay, and propose a multi-channel optoelectronic delay line radar extended target simulation system and method.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a multi-channel optoelectronic delay line radar extended target simulation system, comprising a radar signal receiving and echo signal transmitting module, a frequency mixing and echo Doppler frequency shifting module, a multi-target echo simulation module, a delay module, and an attenuation module;

[0009] The radar signal receiving and echo signal transmitting module includes a receiving antenna, a low-noise amplifier, a DC power supply, a power amplifier and a transmitting antenna; the mixing and echo Doppler frequency shift module includes a down-conversion mixer, a local oscillator and an up-conversion mixer; the multi-target echo simulation module includes a multi-channel power splitter and a combiner; and the attenuation module includes a controllable attenuator and a phase shifter;

[0010] The output end of the receiving antenna is connected to the input end of the low noise amplifier, the input end of the transmitting antenna is connected to the output end of the power amplifier, the DC power supply is connected to the low noise amplifier and the power amplifier respectively, the input end of the down-conversion mixer is connected to the output end of the low noise amplifier, the output end of the up-conversion mixer is connected to the input end of the power amplifier, the local oscillator is connected to the down-conversion mixer and the up-conversion mixer respectively, the output end of the down-conversion mixer is connected to the input end of the multi-channel power splitter, the input end of the up-conversion mixer is connected to the output end of the combiner, the output end of the multi-channel power splitter is connected to the input end, the output end of the delay module is connected to the input end of the controllable attenuator, the output end of the controllable attenuator is connected to the input end of the phase shifter, and the output end of the phase shifter is connected to the input end of the combiner.

[0011] Furthermore, the number of the delay modules, controllable attenuators and phase shifters is the same;

[0012] The delay module includes an echo delay module or an optical fiber delay line module. The echo delay module includes several radio frequency cables of different lengths. The optical fiber delay line module includes a photoelectric converter, an optical fiber, and an electro-optical converter. If the distance to the simulated target is very far and the radio frequency cable is too long to produce or the cable attenuation is too large, the optical fiber delay line module is used instead of the radio frequency cable.

[0013] The receiving antenna is used to receive radar signals;

[0014] The low noise amplifier is used to amplify the radar signal;

[0015] The DC power supply is used to power the low noise amplifier and the power amplifier; the supply voltage of the DC power supply is +7V;

[0016] The power amplifier is used to amplify the simulated radar echo signal;

[0017] The transmitting antenna is used to convert the processed simulated echo signal from a high-frequency current signal form into an electromagnetic wave form propagating in free space, and then transmit it to the radar receiving antenna to complete the simulation of the target radar echo signal;

[0018] The down-conversion mixer is used to reduce the high-frequency radar signal to an intermediate frequency. The down-conversion mixer is a three-port device with two input ports and one output port, wherein one port inputs a high-frequency current signal, the other port inputs a local oscillator signal, and the output port outputs an intermediate frequency signal.

[0019] The local oscillator is used to generate a local oscillator signal which is input to the local oscillator signal input port of the up-converter and the down-converter;

[0020] The up-conversion mixer is used to convert the processed radar intermediate frequency signal carrying the multi-scattering point distance and scattering cross-section information back into a high-frequency current signal that can be transmitted by the radar; the up-conversion mixer is a three-port device with two input ports and one output port, wherein one port inputs the intermediate frequency current signal, the other port inputs the local oscillator signal, and the output port outputs the high-frequency current signal;

[0021] The multi-way power splitter is used to split the input signal into multiple signals of equal power; the multi-way power splitter has a single-port input and multiple-port outputs, and the isolation of the multi-way power splitter is greater than 20dB;

[0022] The combiner is used to superimpose the delayed and attenuated multi-path signals to form a radar intermediate frequency signal carrying multi-scattering point distance and scattering cross-section information; the combiner has multiple port inputs and one port output;

[0023] The electro-optical converter is used to convert the electrical signal into an optical signal transmitted in the optical fiber, and the optical fiber is used to transmit the optical signal;

[0024] The controllable attenuator is used to control the amplitude of the echo signal to simulate the echo amplitude characteristics of the target;

[0025] The phase shifter is used to control the signal phase offset and add phase information to the echo signal to simulate the mutual coupling between multiple point targets or multiple scattering center echoes of electrically large targets;

[0026] The number of branches of the power divider is determined according to the number of echoes, the Doppler frequency is determined according to the speed of the target to be simulated, the delay line length of the echo delay module is determined according to the distance between each echo point and the radar, and the attenuation of the controllable attenuator is determined according to the attenuation of the echo amplitude;

[0027] The radar signal receiving and echo signal transmitting module receives the radar signal, which is converted into an intermediate frequency signal through the mixing and echo Doppler frequency shift module. The intermediate frequency signal is converted into a multi-channel intermediate frequency signal through the multi-target echo simulation module. The multi-channel intermediate frequency signal passes through the delay module and the attenuation module to delay and attenuate each branch signal. The delayed and attenuated multi-channel intermediate frequency signal passes through the multi-target echo simulation module to generate an intermediate frequency signal carrying multi-target information. The intermediate frequency signal carrying multi-target information passes through the mixing and echo Doppler frequency shift module to load the Doppler frequency shift information to obtain a high-frequency echo signal. The high-frequency echo signal passes through the radar signal receiving and echo signal transmitting module to obtain a simulated target echo signal, thereby completing the simulation of the target echo.

[0028] A multi-channel photoelectric delay line radar extended target simulation method, using the multi-channel photoelectric delay line radar extended target simulation system, includes the following steps:

[0029] The radar range resolution is determined based on the bandwidth of the radar signal or the pulse width of the radar pulse signal;

[0030] Decomposing an electrically large target to be simulated into multiple characteristic echoes according to the radar range resolution to obtain target echo characteristics to be simulated, determining echo parameters according to the target echo characteristics to be simulated, wherein the echo parameters include the number of target echoes, target echo delay, target echo attenuation, and target echo Doppler shift; constructing a transmission signal model of a linear frequency modulated pulse radar target according to the echo parameters; and determining the device selection of the simulation system according to the echo parameters;

[0031] Mixing and converting the received radar signal into an intermediate frequency signal;

[0032] The intermediate frequency signal is converted into a multi-channel intermediate frequency signal by multi-target echo simulation;

[0033] Delaying and attenuating each branch signal of the multi-channel intermediate frequency signal to obtain a delayed and attenuated multi-channel intermediate frequency signal;

[0034] Combining the delayed and attenuated multi-channel intermediate frequency signals to generate an intermediate frequency signal carrying multi-target information;

[0035] The intermediate frequency signal is mixed and transmitted to load Doppler frequency shift information to obtain a simulated target echo signal, completing the simulation of the target echo.

[0036] Furthermore, the calculation formula of the radar range resolution is:

[0037]

[0038] Wherein, Δr is the radar range resolution, B is the bandwidth of the radar signal, τ is the pulse width of the radar pulse signal, and c is the speed of light;

[0039] The calculated distance resolution is compared with the size of the target to be simulated. If the size of the target to be simulated is much smaller than the radar distance resolution, the target to be simulated is simulated with one echo point; if the size of the target to be simulated is larger than the radar resolution, the coordinates of the scattering center position of the target to be simulated are extracted, and the scattering center data are counted at the scattering center position.

[0040] Furthermore, the transmission signal model of the linear frequency modulation pulse radar is:

[0041]

[0042] in, is the transmission signal model of linear frequency modulated pulse radar, is the pulse repetition period, is the pulse width, is the amplitude of the transmitted signal, is the starting frequency of the transmitted signal, k is the frequency modulation slope, n is the number of radar transmitted pulses, m is the total number of radar transmitted pulses, τ is the radar target echo delay, is the target echo Doppler shift caused by the radial velocity of the target movement, and rect() is the rectangular pulse function;

[0043] The target echo delay is:

[0044]

[0045] Among them, τ is the radar target echo delay, R is the target distance, c is the speed of light,

[0046] The delay line length of the delay module is:

[0047]

[0048] in, is the i-th delay line, corresponding to the i-th echo point target, c is the speed of light, τ is the time delay of the radar target echo, and ρ is the distance between the target simulator antenna and the radar;

[0049] The target echo Doppler shift is:

[0050]

[0051] in, is the target echo Doppler shift caused by the radial velocity of the target, V is the radial velocity from the target to the radar, 𝜆 is the wavelength of the radar, f is the radar carrier frequency, and c is the speed of light;

[0052] The local oscillator generates a local oscillation signal with a frequency of:

[0053]

[0054] in, is the frequency of the local oscillator signal up-converted by the target simulator, is the frequency of the local oscillator signal down-converted by the target simulator, The Doppler frequency shift of the target echo caused by the radial velocity of the target movement takes a positive sign when the target to be simulated moves toward the radar direction, and a negative sign otherwise;

[0055] The target echo amplitude attenuation is:

[0056]

[0057] in, is the radar receiver received power, is the radar transmitter power, is the radar transmitting antenna gain, is the radar receiving antenna gain, R is the distance between the radar antenna and the target simulator transceiver antenna, L is the total loss of the signal in space and system, λ is the radar signal wavelength, Full gain for the target simulator;

[0058]

[0059] in, Receive antenna and LNA gain for the target simulator, Transmit antenna and power amplifier gain for the target simulator, is the variable attenuator gain.

[0060] Furthermore, the received radar signal is mixed and converted into an intermediate frequency signal. Specifically, the target simulator receiving antenna receives the free space electromagnetic wave radar signal and converts it into a high-frequency current signal. The high-frequency current signal is amplified by a low-noise amplifier to obtain a high-frequency radar signal. The high-frequency radar signal and the local oscillator signal are input into a mixer for down-conversion to obtain an intermediate frequency signal.

[0061] Furthermore, the intermediate frequency signal is converted into a multi-channel intermediate frequency signal by multi-target echo simulation. Specifically, the intermediate frequency signal is input into a one-to-many power distributor to be converted into a multi-channel intermediate frequency signal with the same power.

[0062] Furthermore, the delay and attenuation of each branch signal of the multi-channel intermediate frequency signal is specifically performed by inputting the multi-channel intermediate frequency signals with the same power into a multi-channel delayed radio frequency cable or a delayed optical fiber module to obtain different delays of each branch signal; in each branch, the different amplitudes of different signals of each branch are obtained by controlling the attenuation amount of the controllable attenuator, and the phase shift amount loading of the phase shifter is controlled in each branch to obtain the phase information of each branch signal.

[0063] Furthermore, the delayed and attenuated multi-channel intermediate frequency signals are combined to generate an intermediate frequency signal carrying multi-target information. Specifically, the multi-channel intermediate frequency signals that have been delayed and attenuated are input into a combiner, and synthesized into one signal in the time domain to obtain an intermediate frequency signal carrying multi-target information.

[0064] Furthermore, the intermediate frequency signal is mixed and transmitted to load Doppler frequency shift information to obtain a simulated target echo signal. Specifically, the intermediate frequency signal carrying multi-target information and the local oscillator signal loaded with Doppler frequency shift are input into a mixer for up-conversion to obtain a high-frequency radar echo signal loaded with Doppler frequency shift information, and then the signal is passed through a power amplifier and a transmitting antenna to obtain a simulated free-space electromagnetic wave radar echo signal.

[0065] Compared with the prior art, the present invention has the following beneficial technical effects:

[0066] The multi-channel photoelectric delay line radar extended target simulation system proposed in this invention does not involve digital-to-analog conversion technology, has wider bandwidth, lower delay, simple structure, low cost, adjustable components, and strong applicability.

[0067] The present invention proposes a multi-channel photoelectric delay line radar extended target simulation method, which simulates multiple targets in a one-dimensional distance direction or simulates multiple scattering points of electrically large-sized targets in the distance upward. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present invention in any way. In addition, the shapes and proportional dimensions of the components in the drawings are only schematic and are used to help understand the present invention, and are not intended to specifically limit the shapes and proportional dimensions of the components of the present invention. In the drawings:

[0069] Figure 1 This is a structural diagram of a multi-channel optoelectronic delay line radar extended target simulation system of the present invention.

[0070] Figure 2 This is a structural diagram of the optical fiber delay module of the multi-channel optoelectronic delay line radar extended target simulation system of the present invention.

[0071] Figure 3 The present invention provides a flow chart of a multi-channel photoelectric delay line radar extended target simulation method.

[0072] Figure 4 This is a flow chart of the scattering center extraction steps of a multi-channel photoelectric delay line radar extended target simulation method of the present invention. DETAILED DESCRIPTION

[0073] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0074] It should be noted that when an element is referred to as being "disposed on" another element, it may be directly on the other element or there may be an element centered thereon. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an element centered thereon. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only embodiments.

[0075] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0076] It should be noted that the terms "first," "second," and the like in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including," "having," and any variations thereof are intended to cover non-exclusive inclusions. For example, a process comprising a series of steps or units, a multi-channel electro-optical delay line radar extended target simulation method, system, product, or apparatus is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to these processes, a multi-channel electro-optical delay line radar extended target simulation method, product, or apparatus.

[0077] Example 1

[0078] See also Figure 1 , a multi-channel optoelectronic delay line radar extended target simulation system, including a radar signal receiving and echo signal transmitting module, a mixing and echo Doppler frequency shift module, a multi-target echo simulation module, a delay module and an attenuation module;

[0079] The radar signal receiving and echo signal transmitting module includes a receiving antenna, a low-noise amplifier, a DC power supply, a power amplifier, and a transmitting antenna. The mixing and echo Doppler frequency shift module includes a down-conversion mixer, a local oscillator, and an up-conversion mixer. The multi-target echo simulation module includes a multi-channel power splitter and a combiner. The attenuation module includes a controllable attenuator and a phase shifter.

[0080] The output end of the receiving antenna is connected to the input end of the low noise amplifier, the input end of the transmitting antenna is connected to the output end of the power amplifier, the DC power supply is connected to the low noise amplifier and the power amplifier respectively, the input end of the down-conversion mixer is connected to the output end of the low noise amplifier, the output end of the up-conversion mixer is connected to the input end of the power amplifier, the local oscillator is connected to the down-conversion mixer and the up-conversion mixer respectively, the output end of the down-conversion mixer is connected to the input end of the multi-channel power splitter, the input end of the up-conversion mixer is connected to the output end of the combiner, the output end of the multi-channel power splitter is connected to the input end, the output end of the delay module is connected to the input end of the controllable attenuator, the output end of the controllable attenuator is connected to the input end of the phase shifter, and the output end of the phase shifter is connected to the input end of the combiner;

[0081] The number of delay modules, controllable attenuators and phase shifters is the same;

[0082] See also Figure 2 , the delay module includes an echo delay module or an optical fiber delay line module, the echo delay module includes several radio frequency cables of different lengths, and the optical fiber delay line module includes an optical-to-electrical converter, an optical fiber, and an electro-optical converter;

[0083] The receiving antenna is used to receive radar signals;

[0084] Low noise amplifier is used to amplify radar signals;

[0085] The DC power supply is used to power the low noise amplifier and the power amplifier;

[0086] The power amplifier is used to amplify the simulated radar echo signal;

[0087] The transmitting antenna is used to convert the processed simulated echo signal from a high-frequency current signal form into an electromagnetic wave form that propagates in free space, and then transmit it to the radar receiving antenna to complete the simulation of the target radar echo signal;

[0088] The down-conversion mixer is used to reduce the high-frequency radar signal to an intermediate frequency;

[0089] The local oscillator is used to generate a local oscillator signal input to the local oscillator signal input port of the up-converter and the down-converter;

[0090] The up-conversion mixer is used to convert the processed radar intermediate frequency signal carrying the multi-scattering point distance and scattering cross-section information back into a high-frequency current signal that can be transmitted by the radar;

[0091] The multi-way power splitter is used to split the input signal into multiple signals of equal power;

[0092] The combiner is used to superimpose the delayed and attenuated multi-path signals to form a radar intermediate frequency signal that carries the distance and scattering cross-section information of multiple scattering points;

[0093] The electro-optical converter is used to convert the electrical signal into an optical signal that is transmitted in the optical fiber, and the optical fiber is used to transmit the optical signal;

[0094] The controllable attenuator is used to control the amplitude of the echo signal to simulate the echo amplitude characteristics of the target;

[0095] The phase shifter is used to control the signal phase offset and add phase information to the echo signal to simulate the mutual coupling between multiple point targets or multiple scattering center echoes of electrically large targets.

[0096] This embodiment utilizes a multi-target echo simulation module to simulate radar echo signals from multiple targets. The delay module and attenuation module allow precise control of the delay time and amplitude of the echo signal, enabling simulation of targets at varying distances and reflection intensities. The frequency mixing and echo Doppler shift module simulates the Doppler shift effect caused by target motion. Components such as down-conversion mixers, up-conversion mixers, multi-channel power splitters, and combiners enable flexible processing and simulation of radar signals. The fiber optic delay line module utilizes photoelectric and electro-optical converters to convert electrical signals into optical signals for transmission through optical fibers and then converts them back into electrical signals. This provides long-distance, low-loss delay, enabling the system to simulate target echoes at greater distances. The system utilizes a modular design, with each module relatively independent from the others, facilitating maintenance and upgrades. Furthermore, the system's simulation capabilities can be easily expanded by increasing the number of delay modules, controllable attenuators, and phase shifters. This system can be used not only in the R&D, testing, and calibration phases of radar systems, but also to simulate complex radar environments, aiding in radar operator training and improving the operational capabilities of radar systems.

[0097] The supply voltage of the DC power supply is +7V;

[0098] The down-conversion mixer is a three-port device with two input ports and one output port. One port inputs a high-frequency current signal, the other port inputs a local oscillator signal, and the output port outputs an intermediate frequency signal.

[0099] The up-conversion mixer is a three-port device with two input ports and one output port. One port inputs the intermediate frequency current signal, the other port inputs the local oscillator signal, and the output port outputs the high frequency current signal.

[0100] The multi-channel power splitter has one-port input and multiple-port output, and the isolation of the multi-channel power splitter is greater than 20dB;

[0101] The combiner has multiple ports input and one port output;

[0102] The number of branches of the power divider is determined according to the number of echoes, the Doppler frequency is determined according to the speed of the target to be simulated, the delay line length of the echo delay module is determined according to the distance between each echo point and the radar, and the attenuation of the controllable attenuator is determined according to the attenuation of the echo amplitude;

[0103] If the simulated target is too far away and the RF cable is too long to produce or the cable attenuation is too large, use a fiber optic delay line module instead of the RF cable;

[0104] The radar signal receiving and echo signal transmitting module receives the radar signal, which is converted into an intermediate frequency signal through the mixing and echo Doppler frequency shift module. The intermediate frequency signal is converted into a multi-channel intermediate frequency signal through the multi-target echo simulation module. The multi-channel intermediate frequency signal passes through the delay module and the attenuation module to delay and attenuate each branch signal. The delayed and attenuated multi-channel intermediate frequency signal passes through the multi-target echo simulation module to generate an intermediate frequency signal carrying multi-target information. The intermediate frequency signal carrying multi-target information passes through the mixing and echo Doppler frequency shift module to load the Doppler frequency shift information to obtain a high-frequency echo signal. The high-frequency echo signal passes through the radar signal receiving and echo signal transmitting module to obtain a simulated target echo signal, thereby completing the simulation of the target echo.

[0105] This embodiment provides a powerful tool for radar system performance evaluation, testing, and calibration, offering high precision, multi-target simulation capabilities, flexible delay and attenuation control, scalability, real-time and dynamic performance, ease of maintenance and upgrades, and a wide range of application scenarios. It accurately simulates radar echo signals, including characteristics such as signal delay, attenuation, and Doppler shift. It can simultaneously simulate radar echo signals from multiple targets. Users can adjust the signal delay and attenuation as needed to simulate targets at different distances and with varying reflection intensities. The system is scalable as needed. The system's simulation capabilities can be easily increased by adding delay modules, controllable attenuators, and phase shifters. When simulating targets at long distances, traditional RF cables may not be viable or may exhibit excessive attenuation. In these cases, the system can replace RF cables with fiber delay line modules to achieve long-distance, low-loss delay. The system processes radar signals in real time and dynamically adjusts simulation parameters to simulate targets of varying speeds and motion. Users can replace or upgrade specific modules as needed without making major changes to the entire system. It can be used not only in the R&D, testing, and calibration phases of radar systems, but also to simulate complex radar environments, help train radar operators, and improve the combat capabilities of radar systems. Furthermore, it can be applied to performance evaluation and simulation of military and civilian radar systems.

[0106] Example 2

[0107] See also Figure 3 A multi-channel photoelectric delay line radar extended target simulation method, using a multi-channel photoelectric delay line radar extended target simulation system in embodiment 1, includes the following steps:

[0108] The radar range resolution is determined based on the bandwidth of the radar signal or the pulse width of the radar pulse signal;

[0109] Decompose the electrically large target to be simulated into multiple characteristic echoes based on the radar range resolution to obtain the target echo characteristics to be simulated. Determine the echo parameters based on the target echo characteristics to be simulated. The echo parameters include the number of target echoes, target echo delay, target echo attenuation, and target echo Doppler shift. Construct a transmission signal model of the linear frequency modulated pulse radar target based on the echo parameters. Determine the device selection for the simulation system based on the echo parameters.

[0110] Mixing and converting the received radar signal into an intermediate frequency signal;

[0111] The intermediate frequency signal is converted into a multi-channel intermediate frequency signal by multi-target echo simulation;

[0112] Delaying and attenuating each branch signal of the multi-channel intermediate frequency signal to obtain a delayed and attenuated multi-channel intermediate frequency signal;

[0113] Combining the delayed and attenuated multi-channel intermediate frequency signals to generate an intermediate frequency signal carrying multi-target information;

[0114] The intermediate frequency signal is mixed and transmitted to load Doppler frequency shift information to obtain a simulated target echo signal, completing the simulation of the target echo.

[0115] The method of this embodiment can accurately simulate radar echo signals, including characteristics such as signal delay, attenuation, and Doppler shift. By decomposing the electrically large target to be simulated into multiple characteristic echoes and determining the echo parameters accordingly, this method can simultaneously simulate the radar echo signals of multiple targets. It allows users to flexibly determine the radar range resolution and echo parameters based on parameters such as the bandwidth of the radar signal and the pulse width of the pulse signal. This provides users with great flexibility and allows adjustments to be made according to different test requirements. Starting from receiving the radar signal, after steps such as mixing, multi-target echo simulation, delay and attenuation processing, combining, and Doppler shift information loading, a simulated target echo signal is finally generated. This systematic processing flow ensures the accuracy and reliability of the simulation. Compared with traditional radar target simulation methods, this method can achieve high-quality radar target simulation in a laboratory environment through precise parameter setting and simulation, thereby avoiding complex and expensive testing in a real environment.

[0116] The calculation formula of radar range resolution is:

[0117]

[0118] Wherein, Δr is the radar range resolution, B is the bandwidth of the radar signal, τ is the pulse width of the radar pulse signal, and c is the speed of light;

[0119] The calculated distance resolution is compared with the size of the target to be simulated. If the size of the target to be simulated is much smaller than the radar distance resolution, the target to be simulated is simulated with one echo point; if the size of the target to be simulated is larger than the radar resolution, the coordinates of the scattering center position of the target to be simulated are extracted, and the scattering center data are counted at the scattering center position.

[0120] The transmission signal model of linear frequency modulated pulse radar is:

[0121]

[0122] in, is the transmission signal model of linear frequency modulated pulse radar, is the pulse repetition period, is the pulse width, is the amplitude of the transmitted signal, is the starting frequency of the transmitted signal, k is the frequency modulation slope, n is the number of radar transmitted pulses, m is the total number of radar transmitted pulses, τ is the radar target echo delay, is the target echo Doppler shift caused by the radial velocity of the target movement, and rect() is the rectangular pulse function;

[0123] The target echo delay is:

[0124]

[0125] Among them, τ is the radar target echo delay, R is the target distance, c is the speed of light,

[0126] The delay line length of the delay module is:

[0127]

[0128] in, is the i-th delay line, corresponding to the i-th echo point target, c is the speed of light, τ is the time delay of the radar target echo, and ρ is the distance between the target simulator antenna and the radar;

[0129] The target echo Doppler shift is:

[0130]

[0131] in, is the target echo Doppler shift caused by the radial velocity of the target, V is the radial velocity from the target to the radar, 𝜆 is the wavelength of the radar, f is the radar carrier frequency, and c is the speed of light;

[0132] The local oscillator generates a local oscillation signal with a frequency of:

[0133]

[0134] in, is the frequency of the local oscillator signal up-converted by the target simulator, is the frequency of the local oscillator signal down-converted by the target simulator, The Doppler frequency shift of the target echo caused by the radial velocity of the target movement takes a positive sign when the target to be simulated moves toward the radar direction, and a negative sign otherwise;

[0135] The target echo amplitude attenuation is:

[0136]

[0137] in, is the radar receiver received power, is the radar transmitter power, is the radar transmitting antenna gain, is the radar receiving antenna gain, R is the distance between the radar antenna and the target simulator transceiver antenna, L is the total loss of the signal in space and system, λ is the radar signal wavelength, Full gain for the target simulator;

[0138]

[0139] in, Receive antenna and LNA gain for the target simulator, Transmit antenna and power amplifier gain for the target simulator, is the variable attenuator gain.

[0140] The received radar signal is mixed and converted into an intermediate frequency signal. Specifically, the target simulator receiving antenna receives the free-space electromagnetic wave radar signal and converts it into a high-frequency current signal. The high-frequency current signal is amplified by a low-noise amplifier to obtain a high-frequency radar signal. The high-frequency radar signal and the local oscillator signal are input into the mixer for down-conversion to obtain an intermediate frequency signal.

[0141] The intermediate frequency signal is converted into a multi-channel intermediate frequency signal by multi-target echo simulation. Specifically, the intermediate frequency signal is input into a one-to-many power distributor to be converted into a multi-channel intermediate frequency signal with the same power.

[0142] Delay and attenuation are performed on each branch signal of the multi-channel intermediate frequency signal. Specifically, the multi-channel intermediate frequency signals with the same power are input into a multi-channel delayed RF cable or a delayed optical fiber module to obtain different delays for each branch signal; the different amplitudes of different signals in each branch are obtained by controlling the attenuation amount of the controllable attenuator in each branch, and the phase shift amount loading of the phase shifter in each branch is controlled to obtain the phase information of each branch signal.

[0143] The delayed and attenuated multi-channel intermediate frequency signals are combined to generate an intermediate frequency signal carrying multi-target information. Specifically, the multi-channel intermediate frequency signals that have been delayed and attenuated are input into a combiner, and synthesized into one signal in the time domain to obtain an intermediate frequency signal carrying multi-target information.

[0144] The intermediate frequency signal is mixed and transmitted to load Doppler frequency shift information to obtain a simulated target echo signal. Specifically, the intermediate frequency signal carrying multi-target information and the local oscillator signal loaded with Doppler frequency shift are input into the mixer for up-conversion to obtain a high-frequency radar echo signal loaded with Doppler frequency shift information. The high-frequency radar echo signal is then passed through a power amplifier and a transmitting antenna to obtain a simulated free-space electromagnetic wave radar echo signal.

[0145] This embodiment provides a powerful tool for performance evaluation, testing, and calibration of radar systems, with advantages such as high-precision simulation capability, multi-target simulation and feature extraction, flexible parameter setting and adjustment, systematic processing flow, a wide range of application scenarios, easy implementation and maintenance, and cost-effectiveness.

[0146] Example 3

[0147] This embodiment provides a multi-channel photoelectric delay line radar extended target simulation method, the flow chart of which is as follows: Figure 3 The specific steps are as follows:

[0148] S1. Determine the radar range resolution Δr based on the radar signal bandwidth B or the radar pulse signal pulse width τ. The specific formula is:

[0149]

[0150] Compare the calculated range resolution with the target size to be simulated. If the target size is much smaller than the radar range resolution, it can be regarded as a point target, and an echo point is used to simulate the target. If the target size is larger than the radar resolution, it is regarded as an extended target, and the scattering center reconstruction theory is needed to extract the scattering center position coordinates of the target, and then the special scattering center related data is counted at the scattering center position. The scattering center extraction steps are as follows: Figure 4 As shown in the figure, an electrically large object has multiple scattering centers, each with different amplitude, phase, and other data. Once these data are determined, the device parameters of each channel are adjusted to simulate these scattering centers. In other words, large targets cannot be simulated with a single echo point; multiple echo points are required. The information from these echo points is the information about the target's scattering centers.

[0151] S2. Determine the number of branches of the power divider based on the number of echo points, determine the Doppler frequency based on the speed of the target to be simulated, determine the delay line length of the echo delay module based on the distance of each echo point from the radar, and determine the attenuation of the controllable attenuator based on the specific echo amplitude attenuation. More specifically, the transmission signal model for the linear frequency modulation pulse radar can be described as:

[0152]

[0153] Where: Tr is the pulse repetition period, Tp is the pulse width, A is the amplitude of the transmitted signal, f0 is the starting frequency of the transmitted signal, k is the frequency modulation slope, n is the number of radar transmitted pulses, and m is the total number of radar transmitted pulses.

[0154] For a linear frequency modulation radar target with a distance of R and a speed of V, its echo signal model can be described as:

[0155]

[0156] Where: τ is the radar target echo delay, f d is the target echo Doppler shift caused by the radial velocity of the target, where:

[0157] The target echo delay model is:

[0158]

[0159] Where: τ is the time delay of the target echo, R is the target distance, and c is the speed of light. Based on the distance between the simulator antenna and the radar, the delay line length of the delay module can be determined as:

[0160]

[0161] Where: ρ is the distance between the target simulator antenna and the radar, L i is the i-th delay line, corresponding to the i-th echo point target.

[0162] The target echo Doppler frequency shift model is:

[0163]

[0164] Where: f d is the echo Doppler shift caused by the target's moving speed, V is the radial velocity from the target to the radar, 𝜆 is the radar's wavelength, f is the radar carrier frequency, and c is the speed of light. The echo Doppler shift is determined based on the radial velocity from the target to the radar to be simulated, thereby determining the local oscillator signal frequency generated by the local oscillator during up-conversion:

[0165]

[0166] Where: f2 is the frequency of the local oscillator signal of the target simulator up-converted, f1 is the frequency of the local oscillator signal of the target simulator down-converted, f d The Doppler frequency shift of the echo caused by the target's moving speed takes a positive sign when simulating the target moving toward the radar, and a negative sign otherwise.

[0167] The target echo amplitude attenuation model is:

[0168]

[0169] Where: P r is the radar receiver receiving power, P t is the radar transmitter power, G t is the radar transmitting antenna gain, G ris the radar receiving antenna gain, R is the distance between the radar antenna and the target simulator transceiver antenna, L is the total loss of the signal in space and system, λ is the radar signal wavelength, G m is the total gain of the target simulator, and its specific expression is:

[0170]

[0171] Where G1 is the target simulator receiving antenna and low noise amplifier gain, G2 is the target simulator transmitting antenna and power amplifier gain, G A The attenuation or gain of the controllable attenuator in the echo signal attenuation module is determined according to the echo amplitude or echo power of the target to be simulated.

[0172] S3. The target simulator receiving antenna receives the free space electromagnetic wave radar signal and converts it into a high-frequency current signal. The high-frequency current signal is amplified by a low-noise amplifier to obtain a high-frequency radar signal. The high-frequency radar signal and the local oscillator signal are input into the mixer for down-conversion to obtain an intermediate frequency signal.

[0173] S4. Input the intermediate frequency signal into a one-to-many power distributor in the multi-target echo simulation module to convert it into multiple intermediate frequency signals with the same power.

[0174] S5. Input multiple intermediate frequency signals with the same power into a delay module, i.e., a multi-channel delayed RF cable or a delayed optical fiber module, so as to achieve different delays for each branch signal; at the same time, control the attenuation of the controllable attenuator in each branch to achieve different amplitudes for different signals in each branch, and at the same time control the phase shift of the phase shifter in each branch to load the phase information of different signals.

[0175] S6. Input the multiple intermediate frequency signals that have been delayed and attenuated into a combiner to combine them into one signal in the time domain, that is, generate an intermediate frequency signal carrying multi-target information.

[0176] S7. The intermediate frequency signal carrying the multi-target information is input into the mixer together with the local oscillator signal loaded with Doppler frequency shift through the mixing module for up-conversion to obtain a high-frequency radar echo signal loaded with Doppler frequency shift information. The high-frequency radar echo signal is finally obtained through the power amplifier and transmitting antenna of the transmitting module to realize the simulation of the target echo.

[0177] This embodiment provides a multi-channel photoelectric delay line radar extended target simulation system. Figure 1, including radar signal reception and echo signal transmission module, mixing and echo Doppler frequency shift module, multi-target echo simulation module, echo delay module, and echo signal attenuation module. The radar signal reception and echo signal transmission module includes a receiving antenna, a low-noise amplifier, a DC power supply, a power amplifier, and a transmitting antenna; the mixing and echo Doppler frequency shift module includes a down-conversion mixer, a local oscillator, and an up-conversion mixer; the multi-target echo simulation module includes a multi-channel power splitter and a combiner; the echo delay module includes an RF cable, and for systems using an optical fiber delay line module, it also includes an optical-to-electrical converter, optical fiber, and an electro-optical converter; the echo signal attenuation module includes a controllable attenuator and a phase shifter.

[0178] The receiving antenna receives radar signals. Radar signals are transmitted in free space as electromagnetic waves. The receiving antenna converts these electromagnetic waves into high-frequency current signals for subsequent processing by other devices.

[0179] The function of a low-noise amplifier (LNA) is to amplify radar signals. Radar signals experience some power loss during transmission through space, making them extremely weak by the time they reach the radar target simulator's receiving antenna. Direct processing of these signals is not possible in this situation, requiring specialized components to amplify the weak input signal while minimizing noise, thereby improving the output signal-to-noise ratio. Therefore, adding a LNA to amplify the radar input signal ensures a higher-quality radar signal for subsequent components without compromising the signal-to-noise ratio.

[0180] A downconversion mixer is a three-port device with two input ports and one output port. One port inputs a high-frequency current signal, the other inputs a local oscillator signal, and the output port outputs an intermediate frequency signal. This downconversion mixer can reduce high-frequency radar signals to an intermediate frequency, making them easier to process.

[0181] A multi-channel power splitter has a single input port and multiple output ports, and can split the input signal into multiple signals of equal power. To minimize the impact of interference between multiple signals on multi-target generation, the power splitter's isolation must meet certain requirements, generally greater than 20dB.

[0182] The default echo delay module is composed of several RF cables of different lengths. The length is determined by the distance between the target to be simulated and the radar antenna. If the distance to the simulated target is very far and the RF cable is too long to produce or the cable attenuation is too large, a fiber optic delay line module can be used instead of the RF cable. The fiber optic delay module structure is shown in the figure. Figure 2 The electro-optical converter converts electrical signals into optical signals that can be transmitted through optical fibers. Optical fibers have low loss and low cost, making them suitable for transmitting optical signals. The photoelectric converter converts optical signals into electrical signals, restoring the delayed signals to electrical signals that the system can process and continue with the following processing.

[0183] The controllable attenuator is used to control the amplitude of the echo signal to simulate the echo amplitude characteristics of the target.

[0184] The phase shifter is used to control the signal phase offset and add phase information to the echo signal to simulate the mutual coupling between multiple point targets or multiple scattering center echoes of electrically large targets.

[0185] The combiner has multiple input ports and one output port, and adds together the delayed and attenuated multi-path signals to form a radar intermediate frequency signal that carries the distance and scattering cross-section information of multiple scattering points.

[0186] The upconversion mixer is also a three-port device, with two input ports and one output port. One port inputs an intermediate frequency (IF) current signal, the other inputs a local oscillator (LO) signal, and the output port outputs a high-frequency current signal. This can convert the processed radar IF signal, which carries information about the distances and scattering cross sections of multiple scattering points, back into a high-frequency current signal suitable for radar transmission.

[0187] Power amplifiers are used to amplify simulated radar echo signals. Radar echo signals undergo power loss in the system through up- and down-mixing, branching, delay, and combining. To ensure sufficient power for transmission through the transmitting antenna, power amplifiers are used to amplify them to a certain degree.

[0188] The transmitting antenna is used to convert the processed simulated echo signal from a high-frequency current signal form into an electromagnetic wave form that propagates in free space, and then transmit it to the radar receiving antenna to complete the simulation of the target radar echo signal.

[0189] The DC power supply provides power for the low noise amplifier and power amplifier, and the typical supply voltage is +7V.

[0190] The local oscillator generates a local oscillation signal for input to the local oscillation signal input port of the up-converter and down-converter. Furthermore, the speed information of the moving target can be simulated by controlling the frequency of the up-converter and down-converter local oscillation signal.

[0191] The core method of this embodiment is to simulate multiple targets through the multipath effect. There are also the following alternatives:

[0192] (1) Full microwave solution: If the radar frequency is low and the delay distance is short, for example, below 6 GHz and 100 m, there is no need for up- and down-conversion. The received signal can be directly amplified and then directly split. Each signal is then delayed and phase-shifted to simulate the scattering of multiple targets. The multiple signals are then synthesized and amplified for output.

[0193] (2) All-optical solution: An all-optical solution can be used, and the system can be directly expanded to 40 GHz. First, the received radar signal is directly amplified and transmitted to the optical fiber. The power is split on the optical path to obtain multiple scattered point signals. Each signal is delayed and then combined. The combined signal is then converted to a microwave signal, amplified and output. This method can achieve a signal bandwidth of 40 GHz, which is suitable for full-band and ultra-wideband (real-time bandwidth > 20 GHz) extended target simulation. In addition, the distance simulation can be from millimeters to 100 kilometers.

[0194] (3) Hybrid solution: First, down-convert the signal to baseband. Then, multiple scattering points are realized in the baseband signal power splitter. Each signal path is delayed to simulate multiple scattering points. Each signal path can be delayed by cable or fiber. For short distances (<50m, microwave signal loss is low), cable delay is used. For long distances (>50m, such as 1km, optical signal loss is low), fiber delay is used. This achieves the simulation of hybrid multiple scattering points.

[0195] This embodiment simulates the number, distance, speed, and scattering cross section of target scattering points by changing parameters such as the delay distance, phase, and amplitude of circuits or optical devices on a purely analog circuit basis without involving digital-to-analog conversion. The system has a simple structure and is far superior to the FDGA-based DRFM solution in terms of response time, modulation bandwidth, and cost.

[0196] Many embodiments and applications beyond the examples provided will be apparent to those skilled in the art upon reading the foregoing description. Therefore, the scope of the present teachings should be determined not with reference to the foregoing description, but rather with reference to the preceding claims, along with the full scope of equivalents to which such claims are entitled. For the purpose of completeness, all articles and references, including the disclosures of patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein from the preceding claims is not a disclaimer of such subject matter, nor should it be interpreted that the applicants did not consider such subject matter to be part of the disclosed inventive subject matter.

[0197] The above content is a further detailed description of the present invention, and it cannot be considered that the specific implementation methods of the present invention are limited to these. For ordinary technicians in the technical field to which the present invention belongs, they can make several simple deductions or substitutions without departing from the concept of the present invention, which should be regarded as belonging to the determined protection scope of the present invention submitted.

Claims

1. A multi-channel optoelectronic delay line radar extended target simulation system, characterized in that: It includes radar signal receiving and echo signal transmitting module, frequency mixing and echo Doppler frequency shift module, multi-target echo simulation module, delay module and attenuation module; The radar signal receiving and echo signal transmitting module includes a receiving antenna, a low-noise amplifier, a DC power supply, a power amplifier and a transmitting antenna; the mixing and echo Doppler frequency shift module includes a down-conversion mixer, a local oscillator and an up-conversion mixer; the multi-target echo simulation module includes a multi-channel power splitter and a combiner; and the attenuation module includes a controllable attenuator and a phase shifter; The output end of the receiving antenna is connected to the input end of the low noise amplifier, the input end of the transmitting antenna is connected to the output end of the power amplifier, the DC power supply is connected to the low noise amplifier and the power amplifier respectively, the input end of the down-conversion mixer is connected to the output end of the low noise amplifier, the output end of the up-conversion mixer is connected to the input end of the power amplifier, the local oscillator is connected to the down-conversion mixer and the up-conversion mixer respectively, the output end of the down-conversion mixer is connected to the input end of the multi-channel power splitter, the input end of the up-conversion mixer is connected to the output end of the combiner, the output end of the multi-channel power splitter is connected to the input end, the output end of the delay module is connected to the input end of the controllable attenuator, the output end of the controllable attenuator is connected to the input end of the phase shifter, and the output end of the phase shifter is connected to the input end of the combiner; The number of the delay modules, controllable attenuators and phase shifters is the same; The delay module includes an echo delay module or an optical fiber delay line module. The echo delay module includes several radio frequency cables of different lengths. The optical fiber delay line module includes a photoelectric converter, an optical fiber, and an electro-optical converter. If the distance to the simulated target is very far and the radio frequency cable is too long to produce or the cable attenuation is too large, the optical fiber delay line module is used instead of the radio frequency cable. The receiving antenna is used to receive radar signals; The low noise amplifier is used to amplify the radar signal; The DC power supply is used to power the low noise amplifier and the power amplifier; the supply voltage of the DC power supply is +7V; The power amplifier is used to amplify the simulated radar echo signal; The transmitting antenna is used to convert the processed simulated echo signal from a high-frequency current signal form into an electromagnetic wave form propagating in free space, and then transmit it to the radar receiving antenna to complete the simulation of the target radar echo signal; The down-conversion mixer is used to reduce the high-frequency radar signal to an intermediate frequency. The down-conversion mixer is a three-port device with two input ports and one output port, wherein one port inputs a high-frequency current signal, the other port inputs a local oscillator signal, and the output port outputs an intermediate frequency signal. The local oscillator is used to generate a local oscillator signal which is input to the local oscillator signal input port of the up-converter and the down-converter; The up-conversion mixer is used to convert the processed radar intermediate frequency signal carrying the multi-scattering point distance and scattering cross-section information back into a high-frequency current signal that can be transmitted by the radar; the up-conversion mixer is a three-port device with two input ports and one output port, wherein one port inputs the intermediate frequency current signal, the other port inputs the local oscillator signal, and the output port outputs the high-frequency current signal; The multi-channel power splitter is used to split the input signal into multiple channels of equal power; The multi-channel power splitter has one-port input and multiple-port outputs, and the isolation of the multi-channel power splitter is greater than 20dB; The combiner is used to superimpose the delayed and attenuated multi-path signals to form a radar intermediate frequency signal carrying multi-scattering point distance and scattering cross-section information; the combiner has multiple port inputs and one port output; The electro-optical converter is used to convert the electrical signal into an optical signal transmitted in the optical fiber, and the optical fiber is used to transmit the optical signal; The controllable attenuator is used to control the amplitude of the echo signal to simulate the echo amplitude characteristics of the target; The phase shifter is used to control the signal phase offset and add phase information to the echo signal to simulate the mutual coupling between multiple point targets or multiple scattering center echoes of electrically large targets; The number of branches of the power divider is determined according to the number of echoes, the Doppler frequency is determined according to the speed of the target to be simulated, the delay line length of the echo delay module is determined according to the distance between each echo point and the radar, and the attenuation of the controllable attenuator is determined according to the attenuation of the echo amplitude; The radar signal receiving and echo signal transmitting module receives the radar signal, which is converted into an intermediate frequency signal through the mixing and echo Doppler frequency shift module. The intermediate frequency signal is converted into a multi-channel intermediate frequency signal through the multi-target echo simulation module. The multi-channel intermediate frequency signal passes through the delay module and the attenuation module to delay and attenuate each branch signal. The delayed and attenuated multi-channel intermediate frequency signal passes through the multi-target echo simulation module to generate an intermediate frequency signal carrying multi-target information. The intermediate frequency signal carrying multi-target information passes through the mixing and echo Doppler frequency shift module to load the Doppler frequency shift information to obtain a high-frequency echo signal. The high-frequency echo signal passes through the radar signal receiving and echo signal transmitting module to obtain a simulated target echo signal, thereby completing the simulation of the target echo.

2. A multi-channel photoelectric delay line radar extended target simulation method, using the multi-channel photoelectric delay line radar extended target simulation system described in claim 1, characterized in that: The following steps are involved: The radar range resolution is determined based on the bandwidth of the radar signal or the pulse width of the radar pulse signal; Decomposing the electrically large target to be simulated into multiple characteristic echoes according to the radar range resolution to obtain the target echo characteristics to be simulated, and determining echo parameters according to the target echo characteristics to be simulated, wherein the echo parameters include the number of target echoes, target echo delay, target echo attenuation, and target echo Doppler shift; Construct a transmission signal model of a linear frequency modulated pulse radar target based on echo parameters; determine the device selection of the simulation system based on echo parameters; Mixing and converting the received radar signal into an intermediate frequency signal; The intermediate frequency signal is converted into a multi-channel intermediate frequency signal by multi-target echo simulation; Delaying and attenuating each branch signal of the multi-channel intermediate frequency signal to obtain a delayed and attenuated multi-channel intermediate frequency signal; Combining the delayed and attenuated multi-channel intermediate frequency signals to generate an intermediate frequency signal carrying multi-target information; The intermediate frequency signal is mixed and transmitted to load Doppler frequency shift information to obtain a simulated target echo signal, completing the simulation of the target echo.

3. The method for simulating extended targets of a multi-channel photoelectric delay line radar according to claim 2, wherein: The calculation formula of the radar range resolution is: Wherein, Δr is the radar range resolution, B is the bandwidth of the radar signal, τ is the pulse width of the radar pulse signal, and c is the speed of light; The calculated distance resolution is compared with the size of the target to be simulated. If the size of the target to be simulated is much smaller than the radar distance resolution, the target to be simulated is simulated with one echo point; if the size of the target to be simulated is larger than the radar resolution, the coordinates of the scattering center position of the target to be simulated are extracted, and the scattering center data are counted at the scattering center position.

4. The method for simulating extended targets of a multi-channel photoelectric delay line radar according to claim 2, wherein: The transmission signal model of the linear frequency modulation pulse radar is: in, is the transmission signal model of linear frequency modulated pulse radar, is the pulse repetition period, is the pulse width, is the amplitude of the transmitted signal, is the starting frequency of the transmitted signal, k is the frequency modulation slope, n is the number of radar transmitted pulses, m is the total number of radar transmitted pulses, τ is the radar target echo delay, is the target echo Doppler shift caused by the radial velocity of the target movement, and rect() is the rectangular pulse function; The target echo delay is: Among them, τ is the radar target echo delay, R is the target distance, c is the speed of light, The delay line length of the delay module is: in, is the i-th delay line, corresponding to the i-th echo point target, c is the speed of light, τ is the time delay of the radar target echo, and ρ is the distance between the target simulator antenna and the radar; The target echo Doppler shift is: in, is the target echo Doppler shift caused by the radial velocity of the target, V is the radial velocity from the target to the radar, 𝜆 is the wavelength of the radar, f is the radar carrier frequency, and c is the speed of light; The local oscillator generates a local oscillation signal with a frequency of: in, is the frequency of the local oscillator signal up-converted by the target simulator, is the frequency of the local oscillator signal down-converted by the target simulator, The Doppler frequency shift of the target echo caused by the radial velocity of the target movement takes a positive sign when the target to be simulated moves toward the radar direction, and a negative sign otherwise; The target echo amplitude attenuation is: in, is the radar receiver received power, is the radar transmitter power, is the radar transmitting antenna gain, is the radar receiving antenna gain, R is the distance between the radar antenna and the target simulator transceiver antenna, L is the total loss of the signal in space and system, λ is the radar signal wavelength, Full gain for the target simulator; in, Receive antenna and LNA gain for the target simulator, Transmit antenna and power amplifier gain for the target simulator, is the variable attenuator gain.

5. The method for simulating extended targets of a multi-channel photoelectric delay line radar according to claim 2, wherein: The received radar signal is mixed and converted into an intermediate frequency signal. Specifically, the target simulator receiving antenna receives the free space electromagnetic wave radar signal and converts it into a high-frequency current signal. The high-frequency current signal is amplified by a low-noise amplifier to obtain a high-frequency radar signal. The high-frequency radar signal and the local oscillator signal are input into a mixer for down-conversion to obtain an intermediate frequency signal.

6. The method for simulating extended targets of a multi-channel photoelectric delay line radar according to claim 5, characterized in that: The intermediate frequency signal is converted into a multi-channel intermediate frequency signal by multi-target echo simulation. Specifically, the intermediate frequency signal is input into a one-to-many power distributor to be converted into a multi-channel intermediate frequency signal with the same power.

7. The method for simulating an extended target using a multi-channel photoelectric delay line radar according to claim 6, wherein: The delay and attenuation of each branch signal of the multi-channel intermediate frequency signal are specifically as follows: the multi-channel intermediate frequency signals with the same power are input into a multi-channel delayed radio frequency cable or a delayed optical fiber module to obtain different delays of each branch signal; the different amplitudes of different signals of each branch are obtained by controlling the attenuation amount of the controllable attenuator in each branch, and the phase shift amount loading of the phase shifter in each branch is controlled to obtain the phase information of each branch signal.

8. The method for simulating extended targets of a multi-channel photoelectric delay line radar according to claim 7, wherein: The delayed and attenuated multi-channel intermediate frequency signals are combined to generate an intermediate frequency signal carrying multi-target information. Specifically, the multi-channel intermediate frequency signals that have been delayed and attenuated are input into a combiner, and are combined into one signal in the time domain to obtain an intermediate frequency signal carrying multi-target information.

9. The method for simulating extended targets of a multi-channel photoelectric delay line radar according to claim 8, characterized in that: The intermediate frequency signal is mixed and transmitted to load Doppler frequency shift information to obtain a simulated target echo signal. Specifically, the intermediate frequency signal carrying multi-target information and the local oscillator signal loaded with Doppler frequency shift are input into a mixer for up-conversion to obtain a high-frequency radar echo signal loaded with Doppler frequency shift information. The high-frequency radar echo signal is then passed through a power amplifier and a transmitting antenna to obtain a simulated free-space electromagnetic wave radar echo signal.

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