CN113433519A - Pulse Doppler radar multi-target echo intermediate frequency signal simulation system and method - Google Patents
Pulse Doppler radar multi-target echo intermediate frequency signal simulation system and method Download PDFInfo
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Abstract
The invention provides a pulse Doppler radar multi-target echo signal simulation system and method, and solves the problems that radar echo signal simulation depends on a complex high-speed circuit and parameter adjustment is inaccurate. The output of the noise and frequency modulation pulse echo generating module in the system is connected to the top layer output module; and finally, outputting a signal which is a multi-target intermediate frequency echo signal of the pulse Doppler radar. The method comprises the steps of constructing a simulation system software framework; selecting a non-transplant subunit; transplanting the necessary transplanting subunit; generating and outputting a noise signal, a frequency modulation pulse echo signal and a multi-target echo signal; and finally outputting the multi-target simulated echo after noise addition. The invention is embedded into the radar programmable platform by software, does not need external complex circuits, and is convenient for transplantation and secondary development due to modular design. The software has simple structure, easy parameter adjustment and easy precise digital analysis, reduces the hardware cost and the field test risk, and is suitable for radar simulation system verification, anti-interference test and the like.
Description
Technical Field
The invention belongs to the technical field of radars, mainly relates to echo simulation of a Doppler radar, and particularly relates to a pulse Doppler radar multi-target intermediate frequency signal simulation system and method, which can be used for simulating detection echo signals of an actual pulse Doppler radar to a target.
Technical Field
With scientific progress in various fields such as semiconductors, radar technology is rapidly developed, and the application field and research content thereof are continuously expanded, relating to various aspects such as civil use, military use and the like. Modern radars not only measure the pitch, azimuth, range of a target, but also include target velocity and other relevant information. Modern radars are various in types, and can be divided into continuous wave radars and pulse radars according to a radar waveform system, wherein a Doppler pulse radar is taken as one of the full-coherent radars, the position and the speed of a moving target are detected by utilizing a Doppler effect, and the radar has strong anti-interference performance. The key technology of radar detection is reception and analysis of target echo, when a radar signal processing prototype is researched and developed to complete the requirement of testing or needs troubleshooting in use work, a target echo simulation signal can be generated by the system and the method, and whether the output result of a radar signal processor is consistent with the parameter of a set target echo is compared, so that whether the prototype works normally is verified.
The radar system is tested by generating target echoes, which is a common test flow in the research and development of modern technical personnel radars, and the main technical problems in the test process of the modern radars include high test hardware cost, special requirements on space environment and the like, and relate to complex software and hardware operation flows. In the existing method, a system for storing and replaying waveforms by directly sampling radio frequency generally needs to consume a larger memory space, needs to adopt a high-speed memory device such as a Digital Radio Frequency Memory (DRFM) and the like, has higher requirements on the memory capacity and the control speed of the device, needs to continuously update and read different address data to generate target echo waveforms when simulating dynamic targets, has a complex signal synthesis flow, and brings inconvenience to subsequent packaging and transplanting of user use and software codes; for a system framework based on a Field Programmable Gate Array (FPGA) and a Digital Signal Processor (DSP) for controlling a direct digital frequency synthesizer (DDS), although the cost is low, the waveform generation is not flexible, and the system framework is limited by factors such as phase truncation stray of a DDS device, additional phase influence of an output analog filter and the like.
The radar echo simulation system based on the hardware platform inevitably needs high-speed digital and analog devices and a large-capacity memory, the signal synthesis process and hardware components are complex, the cost is high, noise and signal stray in a circuit system cannot be fundamentally inhibited, the accuracy of analog signal parameters is also limited by the performance of an analog circuit, and a finished product prototype is not favorable for modular packaging and secondary transplantation of users.
Compared with other simulation methods, the target echo signal simulation simplifies the process and the system structure, has the characteristics of simple software structure, easy parameter adjustment, accurate digital analysis and the like, is very suitable for the fields of radar system verification, radar anti-interference test and the like, and has wide application prospect in the present day of rapid development of computer and on-chip digital simulation.
Disclosure of Invention
The invention aims to provide a pulse Doppler radar multi-target echo intermediate frequency signal simulation system and method which are easy to adjust parameters accurately, simple in signal synthesis process and convenient to package in a modularized mode aiming at the defects of the prior art.
The invention relates to a pulse Doppler radar multi-target intermediate frequency echo signal simulation system which is characterized by comprising a noise generation module, a frequency modulation pulse echo generation module and a top layer output module; the output of the noise generation module is connected to the input end of the top layer output module, the output of the frequency modulation pulse echo generation module is also connected to the input end of the top layer output module, the output of the top layer output module is the output of the simulation system, and the output signal is a pulse Doppler radar multi-target intermediate frequency echo signal; wherein:
the noise generation module is used for generating band-limited white Gaussian noise, and the band-limited range and the amplitude of the white Gaussian noise are adjustable;
the frequency modulation pulse echo generating module is used for generating frequency modulation pulse echo signals of a single target or a plurality of targets, simulating multi-target echoes under a Doppler pulse radar system, and adjusting delay time, Doppler speed and amplitude parameters of the frequency modulation pulse signals of each target;
and the top layer output module is used for adding the noise and the frequency modulation pulse echo signals and removing direct current components to generate finally required pulse Doppler radar multi-target intermediate frequency echo signals.
The invention also relates to a pulse Doppler radar multi-target intermediate frequency signal simulation method, which is realized on any one of the pulse Doppler radar multi-target intermediate frequency signal simulation systems disclosed in claims 1-4, wherein the components in each module are called subunits, and provide programmable on-chip test excitation for a radar system to be tested, and the method is characterized by comprising the following steps of:
step (1), constructing a software framework of a pulse Doppler radar multi-target intermediate frequency signal simulation system:
1.1) constructing a pulse Doppler radar multi-target intermediate frequency signal simulation system: the pulse Doppler radar multi-target intermediate frequency signal simulation system comprises a noise generation module, a frequency modulation pulse echo generation module and a top layer output module; the output of the noise generation module is connected to the input end of the top layer output module, the output of the frequency modulation pulse echo generation module is also connected to the input end of the top layer output module, the output of the top layer output module is the output of the simulation system, and the output signal is a pulse Doppler radar multi-target intermediate frequency echo signal; wherein:
the noise generation module is used for generating band-limited white Gaussian noise, and the band-limited range and the amplitude of the white Gaussian noise are adjustable;
the frequency modulation pulse echo generating module is used for generating frequency modulation pulse echo signals of a single target or a plurality of targets, and the delay time, Doppler velocity and amplitude parameters of the frequency modulation pulse signals of each target can be adjusted;
the top layer output module is used for adding noise and frequency modulation pulse echo signals and removing direct current components to generate finally required pulse Doppler radar multi-target intermediate frequency echo signals;
1.2) realizing a software framework of a pulse Doppler radar multi-target intermediate frequency signal simulation system based on a hardware platform: establishing a software framework of a pulse Doppler radar multi-target intermediate frequency signal simulation system on a field programmable gate array FPGA or a digital signal processor DSP programmable platform, wherein the software framework comprises logic resources, storage resource reservation and signal interface establishment, and the storage resources of a data memory in each system module are reserved on the programmable platform; reserving logic resources in each system module, wherein the logic resources are subunits in each module except the data memory; the signal interface comprises an information interface for simulating a target, a pulse period trigger signal interface and a data output interface, wherein the information interface parameters of the target to be simulated comprise the delay time, Doppler velocity and amplitude parameters of a target echo, and the information interface parameters are integrally embedded into a programmable hardware platform of the radar system to be tested as embedded software;
step (2) selecting a non-transplanted subunit: before radar multi-target intermediate frequency signal simulation is carried out, a user free transplanting subunit needs to be defined in a system module, and the user free transplanting subunit comprises a band-pass filter and a noise amplitude controller in a noise generation module, wherein the band-pass filter and the noise amplitude controller respectively control the frequency bandwidth and the amplitude of output white Gaussian noise; a frequency modulation amplitude controller in the frequency modulation pulse echo generation module, wherein the frequency modulation amplitude controller controls the amplitude of the frequency modulation pulse echo signal; the top layer output module comprises a direct current excluder and a top layer amplitude controller, the direct current excluder controls whether an output signal contains a direct current component, and the top layer amplitude controller controls the amplitude of the output signal; the rest are the first necessary transplanting subunit; selecting non-transplanted subunits from the user free transplanting subunits according to the test requirements of the radar system to be tested, wherein the rest subunits except the non-transplanted subunit selected by the test requirements of the radar system in the user free transplanting subunits are second subunits which need to be transplanted;
and (3) transplanting the subunit which needs to be transplanted: the pulse Doppler radar multi-target intermediate frequency signal simulation system comprises a noise generation module, a frequency modulation pulse echo generation module and a top layer output module, wherein all subunits except the subunits of each module of the system which is selected not to be transplanted in the step (2) are transplanted according to a system module and a connection sequence, and a first necessary transplanting subunit and a second necessary transplanting subunit are all transplanted, wherein data memory subunits of the noise generation module and the frequency modulation pulse echo generation module are transplanted into storage resources of a programmable platform of a radar system to be tested, subunits of the system module except a data memory are transplanted into logic resources of the programmable platform of the radar system to be tested, and a corresponding number of single-target frequency modulation pulse echo generation modules are instantiated and declared according to the requirement of the number of targets to be simulated;
step (4), noise signal generation: noise signals in the pulse Doppler radar multi-target intermediate frequency signal simulation system are output by a noise generation module, and the noise generation method is based on Box-Muller transformation to finally obtain Gaussian noise with limited bandwidth and adjustable amplitude, wherein the Gaussian noise is used for simulating limited Gaussian white noise in a natural environment and in a receiver channel;
and (5) generating a frequency modulation pulse echo signal: a frequency modulation pulse echo signal in a pulse Doppler radar multi-target intermediate frequency signal simulation system is generated by a frequency modulation pulse echo generating module, and a frequency modulation pulse echo signal generating method is based on the integration and difference principle of trigonometric functions, so that a frequency modulation signal and a phase are respectively generated and resynthesized, the delay time, the phase change and the signal amplitude of the echo signal are controlled, and the echo signal corresponds to the distance, the speed and the signal-to-noise ratio of the echo signal of a target;
and (6) generating and outputting multi-target echo signals: the synthesis processing of noise signals and frequency modulation pulse echoes in the pulse Doppler radar multi-target intermediate frequency signal simulation system is completed by a top layer output module, wherein the frequency modulation pulse echo signals can instantiate a frequency modulation pulse echo generation module for multiple times according to the requirement of an actual test target, multi-target echoes are synthesized, and finally, multi-target simulation echoes after noise addition are output.
The invention solves the problems that the existing radar system has complex verification process, cannot conveniently and accurately control echo parameters and has higher test hardware cost.
Compared with the prior art, the invention has the following advantages:
the method is convenient for the precise control of the simulation target parameters: the invention simulates the radar intermediate frequency echo signal by a full digitalization software method without receiving the influence of external circuit and device noise, and the waveform generation is more accurate.
The transplantation and secondary development of users are facilitated: the system adopts a modular design, each module leads out a control interface, the portability is realized, a user can freely select whether each subsection is transplanted or not according to the actual test requirement, each information of the target to be simulated can be conveniently adjusted by changing interface parameters, the parameter adjustment and maintenance are easy, and the secondary development is realized.
The signal synthesis process is simple, and the resource occupation is less: the invention separates the phase of each echo pulse of the target from the waveform parameter of the frequency modulation signal by utilizing the sum-difference transformation principle of the trigonometric function, and can independently and accurately control the initial phase of the pulse only by changing the input addresses of the sine and cosine function data memory, thereby simulating the phase change of the echo signal, namely the Doppler effect of the moving target, and greatly reducing the hardware occupation resources of the programmable logic device.
The system has low cost, and avoids a high hardware circuit: the invention tests the system to be tested by constructing the software-on-chip system, simplifies the operation process and greatly reduces the cost of external hardware.
Drawings
FIG. 1 is a block diagram of the logical structure of the system of the method of the present invention;
FIG. 2 is a block diagram of a noise generation module of the method of the present invention;
FIG. 3 is a block diagram of a FM echo generation module of the method of the present invention;
FIG. 4 is a block diagram of the top level output module of the method of the present invention;
FIG. 5 is a block diagram of the steps of the method of the present invention.
Detailed Description
The invention is described in detail below with reference to the following figures and specific examples:
example 1
Based on the background and the requirements, the invention seeks to provide a pulse Doppler radar multi-target echo signal simulation system and method which are easy to implement, low in cost, flexible in parameter adjustment, simple in software flow and suitable for indoor test and analysis through research and experiments.
The invention relates to a pulse Doppler radar multi-target intermediate frequency echo signal simulation system, which comprises a noise generation module, a frequency modulation pulse echo generation module and a top layer output module, wherein the noise generation module is connected with the top layer output module; the output of the noise generation module is connected to the top layer output module, the output of the frequency modulation pulse echo generation module is also connected to the top layer output module, the output of the top layer output module is the output of the simulation system, and the output signal is a pulse Doppler radar multi-target intermediate frequency echo signal; wherein:
the noise generation module is used for generating the white Gaussian noise with the limited frequency band, and the limited frequency band range and the amplitude of the white Gaussian noise can be adjusted. Gaussian white noise is synthesized by the principle of Box-Muller transformation, uniformly distributed random sequences need to be input in the Box-Muller transformation, pseudo random sequences can be conveniently generated by a Linear Feedback Shift Register (LFSR) in a programmable logic device to approximate the uniformly distributed random sequences, and the band-limited white noise is generated by a FIR digital filter in a receiver to simulate the band-pass property of a real receiver.
The frequency modulation pulse echo generating module is used for generating frequency modulation pulse echo signals of a single target or a plurality of targets, simulating multi-target echoes under a Doppler pulse radar system, and adjusting delay time, Doppler speed and amplitude parameters of the frequency modulation pulse signals of all the targets. The delay time of a target echo in a radar system is delayed by a counter by taking a Pulse Repetition Interval (PRI) pulse signal as a reference, the simulation of Doppler velocity is realized by a trigonometric function sum-difference transformation principle, and the adjustment of amplitude is realized by the left shift and the right shift of a shift register.
The top layer output module is used for adding noise and frequency modulation pulse echo signals and removing direct current components to generate finally required pulse Doppler radar multi-target intermediate frequency echo signals. The addition is realized by a signed number adder, the direct current is isolated by taking an average value and self-subtracting, and finally the amplitude adjustment is carried out by a shift register to obtain the final signal output.
The invention generates the radar target echo signal by a digitization method based on programmable logic, thereby simplifying the test flow of the radar system and reducing the test cost.
In the prior art, a radar system is usually tested in a mode of acquiring, processing and replaying signals by adopting a high-speed analog-digital converter and a digital-analog converter, and radar radio-frequency signals are usually in gigahertz and higher frequency, so that high requirements are required on the analog-digital converter, the digital-analog converter, a data memory and a physical transmission link, and simultaneously a real application scene needs to be simulated as much as possible in a test environment.
In order to change the current situation, the invention simulates the radar intermediate frequency echo signal to test by a software method on the chip, and does not need to pass through a real transmission link of the radar external radio frequency signal, and for the radar systems with different parameters, the invention can realize targeted adaptation only by modifying the relevant parameters of the software interface of the echo signal simulation system.
The invention relates to a pulse Doppler radar multi-target echo intermediate frequency signal simulation system constructed by a software method, which provides test excitation on a programmable chip for a radar system to be tested, and specifically comprises three modules: the device comprises a noise generation module, a frequency modulation pulse echo generation module and a top layer output module, wherein the noise generation module is used for generating band-limited Gaussian white noise, the frequency modulation pulse echo generation module is used for generating single or multiple target frequency modulation pulse echo signals, and the top layer output module is used for adding the noise and the frequency modulation pulse echo signals and removing direct current components to generate finally required pulse Doppler radar multi-target intermediate frequency echo signals. The invention does not depend on external complex circuits such as a high-speed digital-to-analog converter and a direct digital frequency synthesizer, but is used as a programmable platform with a software system embedded into a chip level, thereby avoiding the interference introduced by an analog circuit.
The advantages of the invention include:
1. the system to be tested is tested by constructing the software-on-chip system, so that the cost of external hardware is greatly reduced, and the operation flow is simplified.
2. The signal generation method adopted by the invention can conveniently adjust the multi-parameter accuracy of the target echo, thereby reducing the programming complexity.
3. The multi-target echo can be conveniently simulated, a modularized echo generating structure is adopted, and only a single-target frequency modulation pulse echo generating module needs to be instantiated for many times.
Example 2
The overall composition and the specific scheme of the pulse Doppler radar multi-target intermediate frequency echo signal simulation system are the same as those of embodiment 1, and the noise generation module in the invention and the interior of the noise generation module form subunits which are all called as a noise generation module and comprise a linear feedback shift register, a cosine function data memory, a logarithmic function data memory, a noise data multiplier, a band-pass filter and a noise amplitude controller; the device comprises a linear feedback shift register, a data memory, a noise data multiplier, a band-pass filter and a noise amplitude controller which are sequentially connected according to a signal transmission direction, wherein the data memory is a cosine function data memory and a logarithm function data memory which are connected in parallel; the noise magnitude controller output is band-limited white gaussian noise. The following are assigned to each subunit in the noise module of the present invention:
and a linear feedback shift register for generating a pseudo random code to be used as an input address of the cosine function data memory and the logarithm function data memory.
And the cosine function data memory is used for storing the quantized data in the single period of the cosine function, and the stored data corresponding to the address is output when a specific address code is input.
And the logarithmic function data memory is used for storing the quantized data of the inverse number of the natural logarithmic function under the root number within the argument value of (0, 1), and outputting the stored data corresponding to the address by inputting a specific address code.
And a noise data multiplier for multiplying the output data of the cosine function data memory and the logarithm function data memory by a signed number to generate white gaussian noise.
And the band-pass filter is used for limiting the frequency band of the output data of the multiplier, is realized by the FIR filter, can be realized by calling an IP core of the FIR digital filter in the programmable logic device, and can be parameterized with the upper limit cut-off frequency and the lower limit cut-off frequency so as to simulate the band-pass filtering action of a radar receiver, thereby generating a narrow-band white noise signal.
And the noise amplitude controller is used for carrying out numerical amplification or reduction on the output data of the band-pass filter, is realized by the shift operation of the arithmetic shift register, and outputs the output data as the final output of the noise generation module, namely Gaussian white noise.
The mathematical principle of Gaussian white noise generation in the noise generation module is Box-Muller transformation, and the formula is described as follows:
in the above formula, n (t) is the Gaussian white noise signal to be generated, X1(t) and X2(t) is two obeys [0, 1]]Random signal, X, uniformly distributed1(t) and X2(t) is shifted by linear feedbackGenerating a bit register, wherein the output of the linear feedback shift register is a pseudo-random signal, the distribution of the pseudo-random signal is approximately considered as uniform distribution, t is a time variable, and t is taken as [0, i-1 ]]The total number of the integers is i,
i sample points of (2) are stored in a cosine function data memory, cos (2 π X)2(t)) i sample points are stored in a logarithmic function data memory, finally the outputs of the two memories are multiplied by a signed multiplier to obtain white Gaussian noise, and the adjustment of the amplitude of the white Gaussian noise is realized by the shifting operation of an arithmetic shift register.
The noise generated by the noise generation module is the noise with limited frequency band, the noise is close to the situation of the actual radar receiver band-pass receiving echo signal as much as possible, the Gaussian distribution is realized by the Box-Muller mathematical transformation method, the generated Gaussian white noise avoids the influence of special frequency distribution in the noise on the subsequent radar processing flow, the linear feedback shift register and the data memory can be conveniently formed and called in the programmable logic device, and the device advantages of a programming platform are fully utilized.
Example 3
The general constitution and the specific scheme of the pulse Doppler radar multi-target intermediate frequency echo signal simulation system are the same as the embodiments 1-2, the frequency modulation pulse echo generating module comprises one or more single-target frequency modulation pulse echo generating modules, one or more single-target frequency modulation pulse echo signals are generated, the inner parts of the single-target frequency modulation pulse echo generating modules form sub-units which are called as the single-target frequency modulation pulse echo generating modules, in the process of generating analog signals, the single-target frequency modulation pulse echo generating modules respectively generate address codes required by four paths of data memories by address accumulators, wherein, the outputs of a real part data memory and a cosine function data memory of a linear frequency modulation signal are respectively connected to a real part multiplier, the outputs of an imaginary part data memory of the linear frequency modulation signal and a sine function data memory of the linear frequency modulation signal are respectively connected to an imaginary part, the output of the real multiplier and the output of the imaginary multiplier are both connected to a subtracter, and the output of the subtracter is connected to a frequency modulation amplitude controller to form a single-path frequency modulation pulse echo signal; and by analogy, the single-target FM echo generation modules arranged in parallel in the same structure generate multiple channels of FM echo signals, and when the FM echo generation modules are multiple channels of FM echo signals, the multiple channels of FM echo signals are output to be used as the output of the FM echo generation module and connected to the input end of the top-layer FM output module.
Put another way, the single-target FM pulse echo generating module comprises an address accumulator, a cosine function data memory, a sine function data memory, a linear FM signal real part data memory, a linear FM signal imaginary part data memory, a real part multiplier, an imaginary part multiplier, a subtracter and a frequency modulation amplitude controller. The output of the address accumulator is synchronously connected to a real part data memory of the linear frequency modulation signal, a cosine function data memory, an imaginary part data memory of the linear frequency modulation signal and a sine function data memory, wherein the outputs of the real part data memory of the linear frequency modulation signal and the cosine function data memory are synchronously connected to a real part multiplier, the outputs of the imaginary part data memory of the linear frequency modulation signal and the sine function data memory are synchronously connected to an imaginary part multiplier, the outputs of the real part multiplier and the imaginary part multiplier are both connected to a subtracter, the output of the subtracter is connected to a frequency modulation amplitude controller, and the output of the subtracter is; the output of the single-target frequency modulation pulse echo generation module is a single-target frequency modulation pulse echo signal, if a multi-target frequency modulation pulse echo signal needs to be generated, such as n target frequency modulation pulse echo signals, the single-target frequency modulation pulse echo generation module is instantiated and declared n times, and the synchronous output of the n single-target frequency modulation pulse echo generation modules is used as the output of the frequency modulation pulse echo generation module and is connected to the input end of an adder of the top-layer output module.
Referring to fig. 3, the single target fm echo generating module of the present invention is configured as follows:
and the address accumulator is used for generating an address code which is accumulated continuously, and the address code is used as an input address of a rear-stage cosine function data memory, a sine function data memory, a chirp signal real part data memory and a chirp signal imaginary part data memory.
And the data memory of the real part of the linear frequency modulation signal is used for storing the quantized data of the real part of the single-pulse linear frequency modulation signal, and the input specific address code outputs the stored data corresponding to the address.
And the data memory of the imaginary part of the linear frequency modulation signal is used for storing the quantized data of the imaginary part of the single-pulse linear frequency modulation signal, and the stored data corresponding to the address is output by inputting a specific address code.
And the cosine function data memory is used for storing the quantized data in the single period of the cosine function, and the stored data corresponding to the address is output when a specific address code is input.
And the sine function data memory is used for storing the quantized data in the single cycle of the cosine function, and the stored data corresponding to the address is output when a specific address code is input.
And the real part multiplier is used for multiplying the output data of the real part data memory and the cosine function data memory of the linear frequency modulation signal by a signed number.
And the imaginary multiplier is used for carrying out signed number multiplication operation on the output data of the imaginary data memory and the sine function data memory of the linear frequency modulation signal.
And the subtracter is used for carrying out signed subtraction operation on the output of the imaginary multiplier of the real multiplier.
And the frequency modulation amplitude controller is used for carrying out numerical value amplification or reduction on the output data of the subtracter, is realized through the shift operation of the arithmetic shift register, and outputs the output data as the final output of the single-target frequency modulation pulse echo generating module, namely a single-target frequency modulation pulse echo signal.
The generation of the frequency modulation echo signal in the single-target frequency modulation pulse echo generation module is realized based on trigonometric function sum-difference transformation, and is described by a mathematical formula as follows:
in the above formula, s (t) is the intermediate frequency modulation of the target to be simulatedFrequency echo signal, A is signal amplitude, t is time variable, f0Is the center frequency of the fm signal, u is the chirp rate,
for the initial phase of the frequency-modulated echo signals of the target, of each echo-pulse signal, when the target to be simulated has a Doppler velocity
The initial phase will change, and t is [0, k-1 ] in the above formula]k integers, cos (2 π f)0t+πut2) The k sample points are stored in a real data memory of the chirp signal sin (2 π f)0t+πut2) The k sample points are stored in a linear chirp imaginary data memory,
get
The k sample points are stored in a real part data memory of the linear frequency modulation signal,
the k sample value points are stored in a data memory of imaginary part of the linear frequency modulation signal, and the target frequency modulation echo signal is divided into a frequency modulation signal component and an initial phase component thereof by a method of trigonometric function transformation, so that only the change of the formula is needed when the Doppler velocity of the target is simulated
Items and
an item.
The invention separates the frequency modulation signal waveform of the target from the phase of each echo pulse by utilizing the sum-difference transformation principle of the trigonometric function, and can independently and accurately control the initial phase of the pulse only by changing the input addresses of the sine and cosine function data memory, thereby simulating the phase change of the echo signal, namely the Doppler effect of the moving target, greatly reducing the hardware occupation resources of the programmable logic device and leading the signal generation flow to be simpler and more convenient; meanwhile, the generation of the target echo signals is in a modular design, when a tester needs to generate multi-target echo signals, only a single-target frequency modulation pulse echo generating module needs to be instantiated and declared for many times, and the flexibility and the transportability of the module in use are improved.
Example 4
The overall composition and the specific scheme of the pulse Doppler radar multi-target intermediate frequency echo signal simulation system are the same as those of the embodiments 1-3, the interior of a top layer output module forms subunits which are all called as a top layer output module, and the top layer output module comprises an adder, a direct current excluder and a top layer amplitude controller; the system comprises an adder, a direct current excluder and a top layer amplitude controller in sequence according to a signal transmission direction, wherein the input of the adder is the output of a noise generation module and the output of a frequency modulation pulse echo generation module; the top output module of the invention is as follows:
and the adder is used for carrying out signed addition operation on the Gaussian noise signal output by the noise generation module and the single-target frequency modulation pulse echo signal or the multi-target frequency modulation pulse echo signal output by the frequency modulation pulse echo generation module.
And the direct current eliminator is used for removing the direct current component in the output signal of the adder and is realized by carrying out signed subtraction operation on the signal to be processed and the average value of the signal to be processed and the signal to be processed.
And the top layer amplitude controller is used for carrying out numerical value amplification or reduction on the output data of the direct current eliminator, and the output of the top layer amplitude controller is used as the final output of the top layer output module through the shifting operation of the arithmetic shift register.
The top output module is used as a top node of the system, organically combines and processes the noise signal and the frequency modulation pulse echo signal, has a clear system structure, has the functions of direct current isolation and amplitude adjustment, and meets the parameter control requirement in the process of general testing.
Example 5
The invention also relates to a pulse Doppler radar multi-target intermediate frequency echo signal simulation method, which is realized on any one of the pulse Doppler radar multi-target intermediate frequency echo signal simulation systems, on-chip test excitation is provided for a programmable chip in a radar system to be tested, and the components in each module are called subunits, which are shown in figure 5 and comprise the following steps:
step (1), constructing a software framework of a pulse Doppler radar multi-target intermediate frequency signal simulation system:
1.1) constructing a pulse Doppler radar multi-target intermediate frequency signal simulation system: the pulse Doppler radar multi-target intermediate frequency signal simulation system comprises a noise generation module, a frequency modulation pulse echo generation module and a top layer output module; the output of the noise generation module is connected to the input end of the top layer output module, the output of the frequency modulation pulse echo generation module is also connected to the input end of the top layer output module, the output of the top layer output module is the output of the simulation system, and the output signal is a pulse Doppler radar multi-target intermediate frequency echo signal; wherein:
the noise generation module is used for generating the white Gaussian noise with the limited frequency band, and the limited frequency band range and the amplitude of the white Gaussian noise can be adjusted.
The frequency modulation pulse echo generating module is used for generating frequency modulation pulse echo signals of a single target or a plurality of targets, simulating multi-target echoes under a Doppler pulse radar system, and adjusting delay time, Doppler speed and amplitude parameters of the frequency modulation pulse signals of all the targets.
The top layer output module is used for adding noise and frequency modulation pulse echo signals and removing direct current components to generate finally required pulse Doppler radar multi-target intermediate frequency echo signals.
1.2) realizing a software framework of a pulse Doppler radar multi-target intermediate frequency signal simulation system based on a hardware platform: establishing a software framework of a pulse Doppler radar multi-target intermediate frequency signal simulation system on a field programmable gate array FPGA or a digital signal processor DSP programmable platform, wherein the software framework comprises logic resources, storage resource reservation and signal interface establishment, and the storage resources of a data memory in each system module are reserved on the programmable platform; reserving logic resources in each system module, wherein the logic resources are subunits in each module except the data memory; the signal interface comprises an information interface for simulating a target, a pulse period trigger signal interface and a data output interface, wherein the information interface parameters of the target to be simulated comprise the delay time, Doppler velocity and amplitude parameters of a target echo, and the information interface parameters are integrally embedded into a programmable hardware platform of the radar system to be tested as embedded software.
Step (2) selecting a non-transplanted subunit: before radar multi-target intermediate frequency signal simulation is carried out, user free transplanting subunits are required to be defined in a system module and comprise a band-pass filter and a noise amplitude controller in a noise generation module, a frequency modulation amplitude controller in a frequency modulation pulse echo generation module, a direct current excluder and a top layer amplitude controller in a top layer output module, and the rest subunits in the system module are first necessary transplanting subunits; the band-pass filter and the noise amplitude controller respectively control the frequency bandwidth and the amplitude of output white Gaussian noise, the frequency modulation amplitude controller controls the amplitude of a frequency modulation pulse echo signal, and the direct current isolator and the top layer amplitude controller respectively control whether a final output signal contains direct current components and signal amplitude. And selecting non-transplanted subunits from the user free transplanting subunits according to the test requirements of the radar system to be tested, wherein the rest subunits except the non-transplanted subunit selected by the test requirements of the radar system in the user free transplanting subunits are the second subunits which need to be transplanted. The first must-transplant subunit and the second must-transplant subunit are collectively referred to as a must-transplant subunit.
And (3) transplanting the necessary transplanting subunits: transplanting all the first and second sub-units to be transplanted, wherein the data memory sub-units of the noise generation module and the FM echo generation module are transplanted into the storage resources of the programmable platform of the radar system to be tested, the sub-units except the data memory in the system module are transplanted into the logic resources of the programmable platform of the radar system to be tested, and instantiating and declaring the corresponding number of single-target FM echo generation modules according to the requirement of the number of targets to be simulated.
Step (4), noise signal generation: noise signals in the pulse Doppler radar multi-target intermediate frequency signal simulation system are output by a noise generation module, and the noise generation method is based on Box-Muller transformation, and finally Gaussian noise with limited bandwidth and adjustable amplitude is obtained and used for simulating limited Gaussian white noise in a natural environment and in a receiver channel.
And (5) generating a frequency modulation pulse echo signal: the frequency modulation pulse echo signal in the pulse Doppler radar multi-target intermediate frequency signal simulation system is generated by a frequency modulation pulse echo generating module, and the frequency modulation pulse echo signal generating method is based on a trigonometric function sum-difference transformation principle, so that the frequency modulation signal and the phase are respectively generated and synthesized, the delay time, the phase change and the signal amplitude of the echo signal can be conveniently controlled, and the delay time, the phase change and the signal amplitude respectively correspond to the distance, the speed and the signal-to-noise ratio of the echo signal of a target.
And (6) generating and outputting multi-target echo signals: the synthesis processing of noise signals and frequency modulation pulse echoes in the pulse Doppler radar multi-target intermediate frequency signal simulation system is completed by a top layer output module, wherein the frequency modulation pulse echo signals can instantiate a frequency modulation pulse echo generation module for multiple times according to the requirements of an actual test target, so that multi-target echoes are synthesized, and finally, multi-target simulated echoes after noise addition are output.
In the prior art, a direct digital frequency synthesis (DDS) mode is mostly adopted to generate a frequency modulated continuous wave or a frequency modulated pulse to simulate a radar target echo, a mode of constantly changing a waveform phase within each pulse repetition interval is adopted for target speed simulation, and for hardware circuit realization, a signal-to-noise ratio of a generated waveform is not easily adjusted digitally through circuit components such as a high-speed digital-to-analog converter and an amplifier, and waveform standardization needs to be performed through amplitude calibration, spectrum signal-to-noise ratio test and the like.
The invention simulates target echo by constructing a software-on-chip system, tests the subsequent radar processing flow in a full digitalization mode, and splits the linear frequency modulation signal and the phase by the expression of the linear frequency modulation waveform through trigonometric function transformation, thereby realizing the independent control of the phase and realizing the Doppler velocity simulation of the radar target echo.
The invention has the advantages that:
1. the system to be tested is tested by constructing the software-on-chip system, so that the cost of external hardware is greatly reduced, and the operation flow is simplified.
2. The full-digital test flow can avoid the interference of an external hardware circuit, enhance the reliability of the test and ensure that the parameter adjustment of the analog echo is more convenient and accurate.
3. Through the transformation formula of the trigonometric function, the phase of the frequency modulation echo signal is separated from the signal expression, so that the phase of the signal to be simulated can be controlled independently, and the complexity of the Doppler velocity simulation process of the radar target echo is reduced.
Example 6
The pulse Doppler radar multi-target intermediate frequency echo signal simulation system and method are the same as embodiments 1-5, the noise signal generation described in step (4) is transplanted to a linear feedback shift register of a noise generation module of a programmable platform to generate a pseudo-random address code, i.e. evenly distributed random numbers, which serve as address codes for the cosine-function data memory and the logarithm-function data memory, the data corresponding to the addresses are respectively output, the data are signed numbers, signed number multiplication operation is carried out through a multiplier, the output of the multiplier is quantized Gaussian white noise, the Gaussian white noise passes through an FIR band-pass filter to simulate the band-pass filtering action of a radar receiver and generates the Gaussian white noise with limited frequency band, an amplitude control module realizes amplitude adjustment of the Gaussian white noise through left and right shifting of a shift register, and the output of a noise amplitude control module is used as a final output signal of a noise generation module.
Example 7
The system and method for simulating multi-target intermediate frequency echo signals of pulse doppler radar are the same as those in embodiments 1-6, and the address accumulator transplanted in the fm echo generating module of the programmable platform generates address codes cyclically and periodically, the address codes are input into the real part data memory, the cosine function data memory, the real part data memory and the cosine function data memory of the chirp signal, the output data of the real part data memory and the cosine function data memory of the chirp signal are multiplied by signed numbers through the real part multiplier, the output data of the imaginary part data memory and the sine function data memory of the chirp signal are multiplied by signed numbers through the imaginary part multiplier, the output data of the real part multiplier and the imaginary part multiplier are subtracted by the subtracter, the amplitude control module adjusts the amplitude of the output signal of the subtracter through the left-right shifting of the shift register, and the frequency modulation amplitude controller is finally used as the output signal of the frequency modulation pulse echo generation module.
Example 8
The pulse doppler radar multi-target intermediate frequency echo signal simulation system and method are the same as embodiments 1-7, the multi-target echo signal generation and output in step (6), a frequency modulation pulse echo generation module transplanted to a programmable platform is instantiated for multiple times according to test requirements to obtain a multi-target frequency modulation pulse echo signal, the multi-target frequency modulation pulse echo signal and a gaussian noise signal are subjected to signed number addition operation through an adder, the output of the adder is connected to a top layer direct current isolator, the direct current isolator removes direct current components in the signal by performing signed subtraction operation on an input signal and an average value of the input signal, amplitude adjustment is performed through a top layer amplitude controller to serve as an output signal of a top layer output module, and the output signal is a final output signal of the pulse doppler radar multi-target intermediate frequency echo signal simulation system and method.
The present invention will be further explained by combining the pulse Doppler radar multi-target intermediate frequency echo signal simulation system and method
Example 9
The pulse Doppler radar multi-target intermediate frequency echo signal simulation system and the method are the same as the embodiment 1-8,
the invention is described in further detail below with reference to the following figures and specific examples:
referring to fig. 1, a pulse doppler radar multi-target echo signal simulation method includes a noise generation module, a frequency modulation pulse echo generation module, and a top layer output module.
The noise generation module generates white Gaussian noise, and can set the frequency band limit range and the amplitude of the noise. The frequency modulation pulse echo generating module generates a frequency modulation pulse signal, simulates multi-target echoes under a Doppler pulse radar system, and can set echo pulse quantity, echo delay time, Doppler speed and echo amplitude parameters; the top output module sums the noise and the frequency modulation pulse echo signals and removes direct current components to generate finally required echo simulation signals;
referring to fig. 2, the noise generation module includes a linear feedback shift register, a cosine function data memory, a logarithm function data memory, a multiplier, a band-pass filter, and an amplitude control module;
the linear feedback shift register is used for generating a pseudo-random code which is used as an input address of the cosine function data memory and the logarithm function data memory;
the cosine function data memory is used for storing quantized data in a cosine function single period, and inputting a specific address code to output the stored data corresponding to the address;
the logarithm function data memory is used for storing quantized data of the square root of the inverse number of the natural logarithm function in the argument value (0, 1), inputting a specific address code and outputting the stored data corresponding to the address;
the multiplier is used for multiplying the output data of the cosine function data memory and the logarithm function data memory by signed number;
the band-pass filter is used for limiting the frequency band of the output data of the multiplier, the band-pass filter is realized by an FIR filter, the upper limit cut-off frequency and the lower limit cut-off frequency of the band-pass filter can be set in a parameterization mode, and the band-pass filtering action of a radar receiver is simulated, so that a narrow-band white noise signal is generated;
the amplitude control module is used for carrying out numerical value amplification or reduction on output data of the band-pass filter, the numerical value amplification or reduction is realized through the shifting operation of the arithmetic shift register, and the output of the amplitude control module is used as the final output of the noise generation module;
referring to fig. 3, the fm echo generating module includes an address accumulator, a cosine function data memory, a sine function data memory, a chirp signal real part data memory, a chirp signal imaginary part data memory, a multiplier a, a multiplier B, a subtractor, and an amplitude control module;
the address accumulator is used for generating an address code which is accumulated continuously, and the address code is used as an input address of a rear-stage cosine function data memory, a sine function data memory, a linear frequency modulation signal real part data memory and a linear frequency modulation signal imaginary part data memory.
The data memory of the real part of the linear frequency modulation signal is used for storing the quantized data of the real part of the single-pulse linear frequency modulation signal, and the stored data corresponding to the address is output by inputting a specific address code;
the linear frequency modulation signal imaginary part data memory is used for storing the quantitative data of the single pulse linear frequency modulation signal imaginary part, and the stored data corresponding to the address is output by inputting a specific address code;
the cosine function data memory is used for storing quantized data in a cosine function single period, and inputting a specific address code to output the stored data corresponding to the address;
the sine function data memory is used for storing the quantized data in the single period of the cosine function, and inputting a specific address code to output the stored data corresponding to the address;
the multiplier A is used for multiplying the output data of the real part data memory and the cosine function data memory of the linear frequency modulation signal by signed number;
the multiplier B is used for carrying out signed number multiplication operation on output data of the linear frequency modulation signal imaginary part data memory and the sine function data memory;
the subtracter is used for carrying out signed number subtraction operation on the output of the multiplier B of the multiplier A;
the amplitude control module is used for carrying out numerical value amplification or reduction on output data of the subtracter, the numerical value amplification or reduction is realized through the shifting operation of the arithmetic shift register, and the output of the amplitude control module is used as the final output of the frequency modulation pulse echo generating module;
referring to fig. 4, the top output module includes an adder, a dc blocking module, and an amplitude control module;
the adder is used for carrying out signed addition operation on the Gaussian noise signals output by the noise generation module and the multi-target frequency modulation pulse echo signals output by the multiple frequency modulation pulse echo generation modules;
the direct current blocking and dividing module is used for removing direct current components in the output signal of the adder and is realized by carrying out signed subtraction operation on the signal to be processed and the average value of the signal to be processed and the signal to be processed;
the amplitude control module is used for carrying out numerical value amplification or reduction on output data of the direct current blocking module, the numerical value amplification or reduction is realized through the shift operation of the arithmetic shift register, and the output of the amplitude control module is used as the final output of the top output module;
in the pulse radar multi-target signal simulation method, the multiple frequency modulation pulse echo generating modules are generated by module instantiation statement, and the phase and amplitude parameters of echo pulses can be adjusted by instantiated entry parameters.
The invention provides a pulse Doppler radar multi-target echo signal simulation system and a method, which belong to the technical field of radar and can be used for simulating a detection echo signal of an actual pulse Doppler radar to a target, wherein the system comprises a noise generation module, a frequency modulation pulse echo generation module and a top layer output module, the noise generation module generates a frequency band limited Gaussian white noise, and the frequency band limited range and the amplitude of the noise can be set; the frequency modulation pulse echo generating module generates a frequency modulation pulse signal, simulates multi-target echoes under a Doppler pulse radar system, and can set echo pulse quantity, echo delay time, Doppler speed and echo amplitude parameters; the top output module sums the noise and the frequency modulation pulse echo signals and removes direct current components to generate finally required echo simulation signals; the invention has the characteristics of simple software structure, easy parameter adjustment, accurate digital analysis and the like, reduces the hardware cost and the field test risk, and is very suitable for the fields of system verification, radar anti-interference test and the like after the simulation generation of radar signals.
The following is a description of the operation of the present invention:
example 10
The pulse Doppler radar multi-target intermediate frequency echo signal simulation system and the method are the same as the embodiment 1-9, and the test scheme of the frequency modulation pulse radar multi-target echo signal simulation method comprises the following steps:
step (1), constructing a software framework of a pulse Doppler radar multi-target intermediate frequency signal simulation system:
1.1) constructing a pulse Doppler radar multi-target intermediate frequency signal simulation system: the pulse Doppler radar multi-target intermediate frequency signal simulation system comprises a noise generation module, a frequency modulation pulse echo generation module and a top layer output module; the output of the noise generation module is connected to the input end of the top layer output module, the output of the frequency modulation pulse echo generation module is also connected to the input end of the top layer output module, the output of the top layer output module is the output of the simulation system, and the output signal is a pulse Doppler radar multi-target intermediate frequency echo signal; wherein:
the noise generation module is used for generating band-limited white Gaussian noise, and the band-limited range and the amplitude of the white Gaussian noise are adjustable;
the frequency modulation pulse echo generating module is used for generating frequency modulation pulse echo signals of a single target or a plurality of targets, and the delay time, Doppler velocity and amplitude parameters of the frequency modulation pulse signals of each target can be adjusted;
the top layer output module is used for adding noise and frequency modulation pulse echo signals and removing direct current components to generate finally required pulse Doppler radar multi-target intermediate frequency echo signals;
1.2) realizing a software framework of a pulse Doppler radar multi-target intermediate frequency signal simulation system based on a hardware platform: establishing a software framework of a pulse Doppler radar multi-target intermediate frequency signal simulation system on a field programmable gate array FPGA or a digital signal processor DSP programmable platform, wherein the software framework comprises logic resources, storage resource reservation and signal interface establishment, and the storage resources of a data memory in each system module are reserved on the programmable platform; reserving logic resources in each system module, wherein the logic resources are subunits in each module except the data memory; the signal interface comprises an information interface for simulating a target, a pulse period trigger signal interface and a data output interface, wherein the information interface parameters of the target to be simulated comprise the delay time, Doppler velocity and amplitude parameters of a target echo, and the information interface parameters are integrally embedded into a programmable hardware platform of the radar system to be tested as embedded software;
step (2) selecting a non-transplanted subunit: before radar multi-target intermediate frequency signal simulation is carried out, a user free transplanting subunit is defined in a system module and comprises a band-pass filter and a noise amplitude controller in a noise generation module, a frequency modulation amplitude controller in a frequency modulation pulse echo generation module, a direct current isolator and a top layer amplitude controller in a top layer output module; the rest subunits are the first necessary transplanting subunits; selecting non-transplanted subunits from the user free transplanting subunits according to the test requirements of the radar system to be tested, wherein the rest subunits are second necessary transplanting subunits except the non-transplanted subunit selected by the test requirements of the radar system in the user free transplanting subunits;
and (3) transplanting the necessary transplanting subunits: transplanting all the first and second necessary transplanting subunits, wherein the data memory subunits of the noise generation module and the frequency modulation pulse echo generation module are transplanted into the storage resources of the programmable platform of the radar system to be tested, the subunits of the system module except the data memory are transplanted into the logic resources of the programmable platform of the radar system to be tested, and instantiating and declaring the single-target frequency modulation pulse echo generation modules with corresponding number according to the requirement of the number of targets to be simulated;
step (4), noise signal generation: noise signals in the pulse Doppler radar multi-target intermediate frequency signal simulation system are output by a noise generation module, and the noise generation method is based on Box-Muller transformation to finally obtain Gaussian noise with limited bandwidth and adjustable amplitude, wherein the Gaussian noise is used for simulating limited Gaussian white noise in a natural environment and in a receiver channel;
and (5) generating a frequency modulation pulse echo signal: the frequency modulation pulse echo signal in the pulse Doppler radar multi-target intermediate frequency signal simulation system is generated by a frequency modulation pulse echo generating module, and the frequency modulation pulse echo signal generating method is based on a trigonometric function sum-difference transformation principle, so that the frequency modulation signal and the phase are respectively generated and resynthesized, the delay time, the phase change and the signal amplitude of the echo signal can be conveniently controlled, and the distance, the speed and the echo signal to noise ratio of a target are respectively corresponding;
and (6) generating and outputting multi-target echo signals: the synthesis and processing of noise signals and frequency modulation pulse echoes in the pulse Doppler radar multi-target intermediate frequency signal simulation system are completed by a top layer output module, wherein the frequency modulation pulse echo signals instantiate a frequency modulation pulse echo generation module for multiple times according to the requirements of an actual test target, multi-target echoes are synthesized, and finally, multi-target simulation echoes after noise addition are output. The pulse Doppler radar multi-target intermediate frequency signal simulation system is based on a Field Programmable Gate Array (FPGA) or a Digital Signal Processor (DSP) programmable platform, provides on-chip test excitation for a processor of a radar signal processing system to be tested, does not depend on an external radio frequency device and a processing circuit, only enough logic gate resources and memory space need to be reserved, interface parameters comprise information of a simulation target, a pulse period trigger signal and a data output interface, and the interface parameters are integrally used as an embedded software module and embedded into the system to be tested;
in summary, the system and the method for simulating the multi-target echo signal of the pulse doppler radar solve the problems that in the prior art, the radar echo signal simulation depends on a complex high-speed circuit, the parameter adjustment is not accurate enough, and the user transplantation and secondary development are not easy to realize. The simulation system comprises a noise generation module, a frequency modulation pulse echo generation module and a top layer output module; the output of the noise generation module is connected to the input end of the top layer output module, the output of the frequency modulation pulse echo generation module is also connected to the input end of the top layer output module, the output of the top layer output module is the output of the simulation system, and the output signal is a pulse Doppler radar multi-target intermediate frequency echo signal. The simulation method comprises the steps of constructing a software framework of a pulse Doppler radar multi-target intermediate frequency signal simulation system; selecting a subunit not to be transplanted; transplanting the necessary transplanting subunits; generating a noise signal; generating a frequency modulation pulse echo signal; generating and outputting multi-target echo signals; and the user instantiates the frequency modulation pulse echo generating module for multiple times according to the requirement of the actual test target, synthesizes multi-target echoes, and finally outputs the multi-target simulated echoes after noise addition. The invention embeds the software system into the programmable platform of the radar to be tested, does not need an external complex high-speed circuit any more, prevents the inherent interference of a hardware circuit, adopts the modularized design and leads out a parameter control interface, and is convenient for transplantation and secondary development. The invention has simple software structure, easy parameter adjustment and easy precise digital analysis, reduces the hardware cost and the field test risk, and is suitable for the fields of system verification, radar anti-interference test and the like after the simulation generation of radar signals.
The foregoing description has described specific embodiments of the present invention. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by those skilled in the art within the scope of the appended claims without departing from the spirit of the invention.
Claims (8)
1. A pulse Doppler radar multi-target intermediate frequency echo signal simulation system is characterized by comprising a noise generation module, a frequency modulation pulse echo generation module and a top layer output module; the output of the noise generation module is connected to the input end of the top layer output module, the output of the frequency modulation pulse echo generation module is also connected to the input end of the top layer output module, the output of the top layer output module is the output of the simulation system, and the output signal is a pulse Doppler radar multi-target intermediate frequency echo signal; wherein:
the noise generation module is used for generating band-limited white Gaussian noise, and the band-limited range and the amplitude of the white Gaussian noise are adjustable;
the frequency modulation pulse echo generating module is used for generating frequency modulation pulse echo signals of a single target or a plurality of targets, and the delay time, Doppler velocity and amplitude parameters of the frequency modulation pulse signals of each target can be adjusted;
and the top layer output module is used for adding the noise and the frequency modulation pulse echo signals and removing direct current components to generate finally required pulse Doppler radar multi-target intermediate frequency echo signals.
2. The pulse Doppler radar multi-target intermediate frequency echo signal simulation system according to claim 1, wherein the noise generation module and the noise generation module constitute sub-units which are called as a noise generation module, and are sequentially connected with a linear feedback shift register, a data memory, a noise data multiplier, a band-pass filter and a noise amplitude controller according to a signal transmission direction, wherein the data memory is a cosine function data memory and a logarithm function data memory which are connected in parallel; the noise amplitude controller output is band-limited white gaussian noise;
the linear feedback shift register is used for generating a pseudo-random code which is used as an input address of the cosine function data memory and the logarithm function data memory;
the cosine function data memory is used for storing quantized data in a cosine function single period, and inputting a specific address code to output the stored data corresponding to the address;
the logarithm function data memory is used for storing the quantized data of the inverse number of the natural logarithm function under the root number in the argument value (0, 1), and inputting a specific address code to output the stored data corresponding to the address;
the noise data multiplier is used for carrying out signed number multiplication on output data of the cosine function data memory and the logarithm function data memory;
the band-pass filter is used for limiting the frequency band of the output data of the multiplier, the band-pass filter is realized by an FIR filter, the upper limit cut-off frequency and the lower limit cut-off frequency of the band-pass filter can be set in a parameterization mode, and the band-pass filtering action of a radar receiver is simulated, so that a narrow-band white noise signal is generated;
the noise amplitude controller is used for carrying out numerical value amplification or reduction on output data of the band-pass filter, the numerical value amplification or reduction is realized through the shifting operation of the arithmetic shift register, and the output of the noise amplitude controller is used as the final output of the noise generation module, namely Gaussian white noise.
3. The pulsed doppler radar multi-target intermediate frequency echo signal simulation system according to claim 1, wherein the fm echo generation module comprises one or more single-target fm echo generation modules for generating one or more single-target fm echo signals, and the single-target fm echo generation modules are internally configured as sub-units called single-target fm echo generation modules, wherein the single-target fm echo generation modules comprise an address accumulator, a cosine function data memory, a sine function data memory, a chirp signal real part data memory, a chirp signal imaginary part data memory, a real part multiplier, an imaginary part multiplier, a subtracter, and a fm amplitude controller; the output of the address accumulator is synchronously connected to a real part data memory of the linear frequency modulation signal, a cosine function data memory, an imaginary part data memory of the linear frequency modulation signal and a sine function data memory, wherein the outputs of the real part data memory of the linear frequency modulation signal and the cosine function data memory are synchronously connected to a real part multiplier, the outputs of the imaginary part data memory of the linear frequency modulation signal and the sine function data memory are synchronously connected to an imaginary part multiplier, the outputs of the real part multiplier and the imaginary part multiplier are both connected to a subtracter, the output of the subtracter is connected to a frequency modulation amplitude controller, and the output of the subtracter is a single-target frequency modulation pulse echo signal; the output of the single-target frequency modulation pulse echo generation module is a single-target frequency modulation pulse echo signal, if a multi-target frequency modulation pulse echo signal needs to be generated, such as n target frequency modulation pulse echo signals, the single-target frequency modulation pulse echo generation module is instantiated and declared n times, and the synchronous output of the n single-target frequency modulation pulse echo generation modules is used as the output of the frequency modulation pulse echo generation module and is connected to the input end of an adder of the top-layer output module.
The single-target frequency modulation pulse echo generating module is used for generating address codes required by four paths of data memories by an address accumulator in the process of generating an analog signal, wherein the outputs of a real part data memory and a cosine function data memory of a linear frequency modulation signal are respectively connected to a real part multiplier, the outputs of an imaginary part data memory and a sine function data memory of the linear frequency modulation signal are respectively connected to an imaginary part multiplier, the outputs of the real part multiplier and the imaginary part multiplier are both connected to a subtracter, and the output of the subtracter is connected to a frequency modulation amplitude controller to form a single path of frequency modulation pulse echo signal; and by analogy, the single-target FM echo generation modules arranged in parallel in the same structure generate multiple channels of FM echo signals, and when the FM echo generation modules are multiple channels of FM echo signals, the multiple channels of FM echo signals are output to be used as the output of the FM echo generation module and connected to the input end of the top-layer FM output module.
4. The pulse Doppler radar multi-target intermediate frequency echo signal simulation system according to claim 1, wherein the top layer output module internally constitutes subunits which are all called as a top layer output module, and sequentially comprises an adder, a direct current divider and a top layer amplitude controller according to a signal transmission direction, wherein the input of the adder is the output of the noise generation module and the output of the frequency modulation pulse echo generation module; wherein:
the adder is used for carrying out signed addition operation on the Gaussian noise signal output by the noise generation module and the single-target frequency modulation pulse echo signal or the multi-target frequency modulation pulse echo signal output by the frequency modulation pulse echo generation module;
the direct current eliminator is used for removing direct current components in the output signal of the adder and is realized by carrying out signed subtraction operation on the signal to be processed and the average value of the signal to be processed;
the top layer amplitude controller is used for carrying out numerical value amplification or reduction on output data of the direct current eliminator and realizing the numerical value amplification or reduction through the shifting operation of the arithmetic shift register, and the output of the top layer amplitude controller is used as the final output of the top layer output module.
5. A pulse Doppler radar multi-target intermediate frequency signal simulation method is realized on any one of the pulse Doppler radar multi-target intermediate frequency signal simulation systems of claims 1-4, and on-chip test excitation is provided for a programmable chip in a radar system to be tested, and the method is characterized by comprising the following steps:
step (1), constructing a software framework of a pulse Doppler radar multi-target intermediate frequency signal simulation system:
1.1) constructing a pulse Doppler radar multi-target intermediate frequency signal simulation system: the pulse Doppler radar multi-target intermediate frequency signal simulation system comprises a noise generation module, a frequency modulation pulse echo generation module and a top layer output module; the output of the noise generation module is connected to the input end of the top layer output module, the output of the frequency modulation pulse echo generation module is also connected to the input end of the top layer output module, the output of the top layer output module is the output of the simulation system, and the output signal is a pulse Doppler radar multi-target intermediate frequency echo signal; wherein:
the noise generation module is used for generating band-limited white Gaussian noise, and the band-limited range and the amplitude of the white Gaussian noise are adjustable;
the frequency modulation pulse echo generating module is used for generating frequency modulation pulse echo signals of a single target or a plurality of targets, and the delay time, Doppler velocity and amplitude parameters of the frequency modulation pulse signals of each target can be adjusted;
the top layer output module is used for adding noise and frequency modulation pulse echo signals and removing direct current components to generate finally required pulse Doppler radar multi-target intermediate frequency echo signals;
1.2) realizing a software framework of a pulse Doppler radar multi-target intermediate frequency signal simulation system based on a hardware platform: establishing a software framework of a pulse Doppler radar multi-target intermediate frequency signal simulation system on a field programmable gate array FPGA or a digital signal processor DSP programmable platform, wherein the software framework comprises logic resources, storage resource reservation and signal interface establishment, and the storage resources of a data memory in each system module are reserved on the programmable platform; reserving logic resources in each system module, wherein the logic resources are subunits in each module except the data memory; the signal interface comprises an information interface for simulating a target, a pulse period trigger signal interface and a data output interface, wherein the information interface parameters of the target to be simulated comprise the delay time, Doppler velocity and amplitude parameters of a target echo, and the information interface parameters are integrally embedded into a programmable hardware platform of the radar system to be tested as embedded software;
step (2) selecting a non-transplanted subunit: before radar multi-target intermediate frequency signal simulation is carried out, a user free transplanting subunit is defined in a system module and comprises a band-pass filter and a noise amplitude controller in a noise generation module, a frequency modulation amplitude controller in a frequency modulation pulse echo generation module, a direct current isolator and a top layer amplitude controller in a top layer output module; the rest subunits are the first necessary transplanting subunits; selecting non-transplanted subunits from the user free transplanting subunits according to the test requirements of the radar system to be tested, wherein the rest subunits are second necessary transplanting subunits except the non-transplanted subunit selected by the test requirements of the radar system in the user free transplanting subunits;
and (3) transplanting the necessary transplanting subunits: transplanting all the first and second necessary transplanting subunits, wherein the data memory subunits of the noise generation module and the frequency modulation pulse echo generation module are transplanted into the storage resources of the programmable platform of the radar system to be tested, the subunits of the system module except the data memory are transplanted into the logic resources of the programmable platform of the radar system to be tested, and instantiating and declaring the single-target frequency modulation pulse echo generation modules with corresponding number according to the requirement of the number of targets to be simulated;
step (4), noise signal generation: noise signals in the pulse Doppler radar multi-target intermediate frequency signal simulation system are output by a noise generation module, and the noise generation method is based on Box-Muller transformation to finally obtain Gaussian noise with limited bandwidth and adjustable amplitude, wherein the Gaussian noise is used for simulating limited Gaussian white noise in a natural environment and in a receiver channel;
and (5) generating a frequency modulation pulse echo signal: the frequency modulation pulse echo signal in the pulse Doppler radar multi-target intermediate frequency signal simulation system is generated by a frequency modulation pulse echo generating module, and the frequency modulation pulse echo signal generating method is based on a trigonometric function sum-difference transformation principle, so that the frequency modulation signal and the phase are respectively generated and resynthesized, the delay time, the phase change and the signal amplitude of the echo signal can be conveniently controlled, and the distance, the speed and the echo signal to noise ratio of a target are respectively corresponding;
and (6) generating and outputting multi-target echo signals: the synthesis and processing of noise signals and frequency modulation pulse echoes in the pulse Doppler radar multi-target intermediate frequency signal simulation system are completed by a top layer output module, wherein the frequency modulation pulse echo signals instantiate a frequency modulation pulse echo generation module for multiple times according to the requirements of an actual test target, multi-target echoes are synthesized, and finally, multi-target simulation echoes after noise addition are output.
6. The method according to claim 5, wherein the noise signal generation of step (4) is performed by transplanting a pseudo random address code, which is an evenly distributed random number, into a linear feedback shift register of a noise generation module of a programmable platform to generate pseudo random address codes, which are address codes of a cosine function data memory and a logarithm function data memory, and which output data corresponding to addresses, respectively, the data are signed numbers, performing signed number multiplication operation by a multiplier, the multiplier outputs quantized white Gaussian noise, the white Gaussian noise simulates the bandpass filtering action of a radar receiver through an FIR bandpass filter to generate band-limited white Gaussian noise, and the amplitude control module realizes amplitude adjustment of the white Gaussian noise through left and right shifting of the shift register, the output of the noise amplitude control module is used as the final output signal of the noise generation module.
7. The method according to claim 5, wherein the FM echo signal of step (5) is transplanted to an address accumulator in the FM echo generation module of the programmable platform to cyclically and periodically generate an address code, the address code is inputted to the real data memory, the cosine function data memory, the real data memory and the cosine function data memory of the chirp signal, the output data of the real data memory and the cosine function data memory of the chirp signal are multiplied by a signed number through a real multiplier, the output data of the imaginary data memory and the sine function data memory of the chirp signal are multiplied by a signed number through an imaginary multiplier, and the output data of the real multiplier and the imaginary multiplier are subtracted by a subtracter, the amplitude control module adjusts the amplitude of the output signal of the subtracter through the left-right shifting of the shift register, and the frequency modulation amplitude controller is finally used as the output signal of the frequency modulation pulse echo generation module.
8. The method according to claim 5, wherein the multi-target echo signals in step (6) are generated and output, a frequency modulation pulse echo generating module transplanted to a programmable platform is instantiated for a plurality of times according to test requirements to obtain multi-target frequency modulation pulse echo signals, signed number addition operation is performed on the multi-target frequency modulation pulse echo signals and Gaussian noise signals through an adder, the output of the adder is connected to a top layer direct current isolator, the direct current isolator performs signed subtraction operation on input signals and the average value of the direct current isolator to remove direct current components in the signals, amplitude adjustment is performed through a top layer amplitude controller to serve as output signals of a top layer output module, and the output signals are final output signals of the system.
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