阅读说明：本技术 基于fpga的雷达回波基带信号产生系统及方法 (Radar echo baseband signal generation system and method based on FPGA ) 是由 任煜 吴彬彬 李洪涛 于 2020-06-02 设计创作，主要内容包括：本发明公开了一种基于FPGA的雷达回波基带信号产生系统及方法,该系统由中频发射信号模块、信号采集模块、回波调制模块和控制模块组成,其中控制模块根据配置的波形参数和运动目标信息对中频发射信号模块和回波调制模块进行控制；中频发射信号模块根据波形参数产生相应的中频发射信号,并输入到信号采集模块；信号采集模块对中频信号进行带通采样和数字下变频形成基带信号；回波调制模块对基带信号进行多普勒调制和距离调制,得到回波基带信号。本发明通过环回的方式在发射信号的基础上叠加运动目标信息,产生雷达回波基带信号,为在室内调试雷达信号处理系统提供了条件。(The invention discloses a radar echo baseband signal generating system and a method based on FPGA, wherein the system consists of an intermediate frequency transmitting signal module, a signal acquisition module, an echo modulation module and a control module, wherein the control module controls the intermediate frequency transmitting signal module and the echo modulation module according to configured waveform parameters and moving target information; the intermediate frequency transmitting signal module generates a corresponding intermediate frequency transmitting signal according to the waveform parameter and inputs the intermediate frequency transmitting signal to the signal acquisition module; the signal acquisition module performs band-pass sampling and digital down-conversion on the intermediate-frequency signal to form a baseband signal; the echo modulation module performs Doppler modulation and distance modulation on the baseband signal to obtain an echo baseband signal. The invention superposes the moving target information on the basis of the transmitted signal in a loopback mode to generate a radar echo baseband signal, thereby providing conditions for debugging a radar signal processing system indoors.)

1. The utility model provides a radar echo baseband signal produces system which characterized in that based on FPGA: the device comprises an intermediate frequency transmitting signal module, a signal acquisition module, an echo modulation module and a control module;

the control module is used for controlling the intermediate frequency transmission signal module and the echo modulation module according to the configured waveform parameters and the moving target information;

the intermediate frequency transmitting signal module is used for generating a corresponding intermediate frequency transmitting signal according to the waveform parameter and inputting the intermediate frequency transmitting signal to the signal acquisition module;

the signal acquisition module is used for performing band-pass sampling and digital down-conversion on the intermediate frequency signal to form a baseband signal;

the echo modulation module is used for carrying out Doppler modulation and distance modulation on the baseband signal according to the speed and distance information output by the control module to obtain an echo baseband signal.

2. A signal generating method of the FPGA-based radar echo baseband signal generating system according to claim 1, comprising the steps of:

the control module controls the intermediate frequency transmitting signal module to generate a corresponding intermediate frequency transmitting signal according to the configured waveform parameters;

the intermediate frequency transmitting signal is input to a signal acquisition module, and band-pass sampling and digital down-conversion are carried out to form a baseband signal;

the echo modulation module performs Doppler modulation and distance modulation on the baseband signal according to the speed and distance information output by the control module to obtain an echo baseband signal.

3. The signal generating method according to claim 2, characterized in that: the control module receives and analyzes the control command, configures the intermediate frequency transmitting signal module according to the waveform parameters in the control command, and solves the distance and the speed of the current echo according to the moving target information in the control command, controls the echo modulation module to generate the target echo moving at a uniform speed, and the implementation steps are as follows:

step 1, inputting an initial distance R of a moving target₀And a radial velocity v;

step 2, judging whether the initial distance and the speed are in the range of distance measurement and speed measurement, if so, entering step 3, otherwise, returning to step 1;

step 3, controlling an echo modulation module to perform Doppler modulation according to the speed information of the target;

step 4, making the scanning times N of the antenna equal to 0;

step 5, making the time parameter T equal to NT, wherein T is an antenna scanning period;

and 6, judging whether the speed of the target is greater than 0, if so, indicating that the target moves towards the direction close to the radar, and setting the distance between the target and the radar to be R-R₀-vt, if not, indicating that the target is moving away from the radar, the target being at a distance R-R from the radar₀+vt；

And 7, judging whether the current distance R of the target is within the range of the distance measurement, if so, modulating the distance according to the current distance of the target, and making N equal to N +1, then returning to the step 5, repeating the step 5 to the step 7, if not, indicating that the target moves to the range-measurement blind area of the radar or exceeds the maximum acting distance of the radar, and finishing the movement track.

4. The signal generating method according to claim 3, characterized in that: the waveform parameters include pulse duration, bandwidth, repetition period, and center frequency.

5. The signal generating method according to claim 2, characterized in that: the intermediate frequency transmitting signal module receives the waveform parameters from the control module and configures the DDS to generate the required transmitting signal according to the waveform parameters.

6. The signal generating method according to claim 2, characterized in that: the signal acquisition module down-converts the intermediate frequency signal to a baseband, and the implementation steps are as follows:

step 1, an intermediate frequency transmitting signal is used as input of a signal acquisition module, the signal acquisition module performs band-pass sampling on the intermediate frequency signal by using an ADC (analog to digital converter) chip to form an intermediate frequency digital signal, and the ADC chip transmits the digital signal to an FPGA (field programmable gate array) through an LVDS (low voltage differential signaling) interface;

and 2, multiplying the intermediate frequency digital signal received by the FPGA by two paths of orthogonal digital local oscillator signals, and obtaining IQ two paths of orthogonal baseband signals through a low-pass filter.

7. The method for generating radar echo baseband signals based on FPGA of claim 2, wherein: the echo modulation module is divided into a Doppler modulation submodule and a distance modulation submodule; the Doppler modulation submodule calculates Doppler frequency according to the speed information of the target and carries out Doppler frequency shift on the baseband signal, and the distance modulation submodule calculates echo delay according to the distance information of the target and carries out distance delay on the baseband signal.

8. The method for generating radar echo baseband signals based on FPGA of claim 7, wherein: the implementation steps of the Doppler modulation submodule are as follows:

step 1, according to a formula f_dCalculating the Doppler frequency shift of the target at 2 v/lambda, wherein lambda is the wavelength;

step 2, generating the frequency f by using a CORDIC algorithm_dSine and cosine digital signals of;

and 3, carrying out complex multiplication on the IQ two-path baseband signals and the sine and cosine signals in the step 2 to obtain echo baseband signals containing Doppler frequency shift.

9. The method for generating radar echo baseband signals based on FPGA of claim 7, wherein: the distance modulation submodule is realized by the following steps:

step 1, calculating the delay tau of the echo relative to a transmitted signal according to a formula 2R-tau c, wherein R is the distance of a target relative to a radar, and c is the speed of light;

step 2, according to the AD sampling frequency f of the signal acquisition module_sDetermining the minimum time unit Δ τ as 1/f_sDividing and rounding the echo delay by the minimum time unit to obtain the number M of delayed sampling points which is tau/delta tau;

and 3, buffering the baseband signals into FIFO, starting counting from 0 by the counter, and reading out the baseband signals when M is counted, so that echo baseband signals containing distance delay can be obtained.

Technical Field

The invention belongs to the technical field of radar testing, and particularly relates to a radar echo baseband signal generation system and method based on an FPGA.

Background

The radar signal processing system is an important component of a radar system, and specifically, the signal processing system receives an echo from a target, performs corresponding digital signal processing, and then acquires information such as a distance and a speed of the target. In the development process of the radar signal processing system, the function and the performance of the radar signal processing system need to be verified.

Generally, the function and performance of a signal processing system are usually verified by an external field test, which is affected by factors such as weather and field, and the implementation process consumes a lot of manpower, material resources and resources. The radar simulator simulates an echo signal of a radar and sends the echo signal to the radar, can be used for debugging and verifying a radar system when an external field test condition is not met, and has wide application in the field of radar test, but extra hardware equipment needs to be added in the mode, and research and development cost and period are increased.

Disclosure of Invention

The invention aims to provide a radar echo baseband signal generating system and method based on an FPGA (field programmable gate array), which are used for providing an echo signal for a radar signal processing system and are convenient for indoor debugging.

The technical solution for realizing the purpose of the invention is as follows: a radar echo baseband signal generating system based on FPGA comprises an intermediate frequency transmitting signal module, a signal collecting module, an echo modulating module and a control module;

the control module is used for controlling the intermediate frequency transmission signal module and the echo modulation module according to the configured waveform parameters and the moving target information;

the intermediate frequency transmitting signal module is used for generating a corresponding intermediate frequency transmitting signal according to the waveform parameter and inputting the intermediate frequency transmitting signal to the signal acquisition module;

the signal acquisition module is used for performing band-pass sampling and digital down-conversion on the intermediate frequency signal to form a baseband signal;

the echo modulation module is used for carrying out Doppler modulation and distance modulation on the baseband signal according to the speed and distance information output by the control module to obtain an echo baseband signal.

A radar echo baseband signal generation method based on FPGA comprises the following steps:

the control module controls the intermediate frequency transmitting signal module to generate a corresponding intermediate frequency transmitting signal according to the configured waveform parameters;

the intermediate frequency transmitting signal is input to a signal acquisition module, and band-pass sampling and digital down-conversion are carried out to form a baseband signal;

the echo modulation module performs Doppler modulation and distance modulation on the baseband signal according to the speed and distance information output by the control module to obtain an echo baseband signal.

Furthermore, the control module receives and analyzes the control command, configures the intermediate frequency transmitting signal module according to the waveform parameters in the control command, and calculates the distance and speed of the current echo according to the moving target information in the control command, controls the echo modulation module to generate the target echo moving at a uniform speed, and the implementation steps are as follows:

step 1, inputting an initial distance R of a moving target₀And a radial velocity v;

step 2, judging whether the initial distance and the speed are in the range of distance measurement and speed measurement, if so, entering step 3, otherwise, returning to step 1;

step 3, controlling an echo modulation module to perform Doppler modulation according to the speed information of the target;

step 4, making the scanning times N of the antenna equal to 0;

step 5, making the time parameter T equal to NT, wherein T is an antenna scanning period;

and 6, judging whether the speed of the target is greater than 0, if so, indicating that the target moves towards the direction close to the radar, and setting the distance between the target and the radar to be R-R₀-vt, if not, indicating that the target is moving away from the radar, the target being at a distance R-R from the radar₀+vt；

And 7, judging whether the current distance R of the target is within the range of the distance measurement, if so, modulating the distance according to the current distance of the target, and making N equal to N +1, then returning to the step 5, repeating the step 5 to the step 7, if not, indicating that the target moves to the range-measurement blind area of the radar or exceeds the maximum acting distance of the radar, and finishing the movement track.

Further, the waveform parameters include pulse time width, bandwidth, repetition period, and center frequency.

Further, the intermediate frequency transmitting signal module receives the waveform parameter from the control module, and configures the DDS to generate the required transmitting signal according to the waveform parameter.

Further, the signal acquisition module down-converts the intermediate frequency signal to a baseband, and the implementation steps are as follows:

step 1, an intermediate frequency transmitting signal is used as input of a signal acquisition module, the signal acquisition module performs band-pass sampling on the intermediate frequency signal by using an ADC (analog to digital converter) chip to form an intermediate frequency digital signal, and the ADC chip transmits the digital signal to an FPGA (field programmable gate array) through an LVDS (low voltage differential signaling) interface;

and 2, multiplying the intermediate frequency digital signal received by the FPGA by two paths of orthogonal digital local oscillator signals, and obtaining IQ two paths of orthogonal baseband signals through a low-pass filter.

Furthermore, the echo modulation module is divided into a Doppler modulation submodule and a distance modulation submodule; the Doppler modulation submodule calculates Doppler frequency according to the speed information of the target and carries out Doppler frequency shift on the baseband signal, and the distance modulation submodule calculates echo delay according to the distance information of the target and carries out distance delay on the baseband signal.

The implementation steps of the Doppler modulation submodule are as follows:

step 1, according to a formula f_dCalculating the Doppler frequency shift of the target at 2 v/lambda, wherein lambda is the wavelength;

step 2, generating the frequency f by using a CORDIC algorithm_dSine and cosine digital signals of;

and 3, carrying out complex multiplication on the IQ two-path baseband signals and the sine and cosine signals in the step 2 to obtain echo baseband signals containing Doppler frequency shift.

The distance modulation submodule is realized by the following steps:

step 1, calculating the delay tau of the echo relative to a transmitted signal according to a formula 2R-tau c, wherein R is the distance of a target relative to a radar, and c is the speed of light;

step 2, according to the AD sampling frequency f of the signal acquisition module_sDetermining the minimum time unit Δ τ as 1/f_sDividing and rounding the echo delay by the minimum time unit to obtain the number M of delayed sampling points which is tau/delta tau;

and 3, buffering the baseband signals into FIFO, starting counting from 0 by the counter, and reading out the baseband signals when M is counted, so that echo baseband signals containing distance delay can be obtained.

Compared with the prior art, the invention has the following remarkable advantages: 1) the invention fully utilizes the existing hardware of the radar, does not need to add extra devices, connects the generated intermediate frequency transmitting signal to a receiving end in a loopback mode, performs digital processing after analog-to-digital conversion on the transmitting signal to obtain an echo signal carrying target information, and provides an excitation signal for subsequent echo signal processing; 2) the transmitting waveform is flexible and configurable, pulse signals with different parameters can be rapidly generated, and the application range is wide; 3) the initial state of the target can be flexibly set, and echo signals of the target in static and uniform motion states can be simulated; 4) the method has simple algorithm in the echo modulation process, is easy to realize by using the FPGA, and has high integration level.

Drawings

Fig. 1 is an overall block diagram of a radar echo baseband signal generation system based on an FPGA.

Fig. 2 is a hardware configuration diagram for generating an echo baseband signal.

FIG. 3 is a control module flow diagram.

Fig. 4 is a block diagram of a signal acquisition module.

Figure 5 is a block diagram of an echo modulation module.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

The radar echo baseband signal generating system based on the FPGA is shown in figure 1 and comprises an intermediate frequency signal transmitting module, a signal collecting module, an echo modulating module and a control module. The control module controls the intermediate frequency transmission signal module and the echo modulation module according to the configured waveform parameters and the moving target information; the intermediate frequency transmitting signal module generates a corresponding intermediate frequency transmitting signal according to the waveform parameter and inputs the intermediate frequency transmitting signal to the signal acquisition module; the signal acquisition module performs band-pass sampling and digital down-conversion on the intermediate-frequency signal to form a baseband signal; the echo modulation module performs Doppler modulation and distance modulation on the baseband signal according to the speed and distance information output by the control module to obtain an echo baseband signal.

The hardware structure of the invention is shown in fig. 2, the FPGA receives the control command from the upper computer and analyzes the waveform parameter in the command, the DDS is configured through the SPI interface in combination with the waveform parameter to generate an intermediate frequency transmission signal, the transmission signal is transmitted to the input end of the ADC through the SMA interface to perform analog-to-digital conversion, and the obtained digital signal is transmitted to the FPGA through the LVDS interface and then is subjected to signal processing to obtain an echo baseband signal carrying target information.

The invention also provides a signal generating method based on the system, which comprises the following steps:

the control module controls the intermediate frequency transmitting signal module to generate a corresponding intermediate frequency transmitting signal according to the configured waveform parameters;

the intermediate frequency transmitting signal is input to a signal acquisition module, and band-pass sampling and digital down-conversion are carried out to form a baseband signal;

the echo modulation module performs Doppler modulation and distance modulation on the baseband signal according to the speed and distance information output by the control module to obtain an echo baseband signal.

The flow of the control module is shown in fig. 3, the control module is configured to receive and analyze the control command, and configure the intermediate frequency transmission signal module according to the waveform parameters in the control command; resolving the distance and the speed of the current echo according to the configured moving target information, controlling an echo modulation module and generating a target echo moving at a constant speed; the implementation steps of controlling the echo modulation module are as follows:

step 1, inputting an initial distance R of a moving target₀And a radial velocity v;

step 2, judging whether the initial distance and the speed are in the range of distance measurement and speed measurement, if so, entering step 3, otherwise, returning to step 1;

step 3, controlling an echo modulation module to perform Doppler modulation according to the speed information of the target;

step 4, making the scanning times N of the antenna equal to 0;

step 5, making the time parameter T equal to NT, wherein T is an antenna scanning period;

and 6, judging whether the speed of the target is greater than 0, if so, indicating that the target moves towards the direction close to the radar, and setting the distance between the target and the radar to be R-R₀-vt, if notThis means that the target moves away from the radar and the distance of the target to the radar is R ═ R₀+vt；

And 7, judging whether the current distance of the target is within the range finding range, if so, modulating the distance according to the current distance of the target, and enabling N to be N +1, then returning to the step 5, repeating the step 5 to the step 7, otherwise, indicating that the target moves to the range finding blind area of the radar or exceeds the maximum acting distance of the radar, and finishing the movement track.

The waveform parameters include pulse duration, bandwidth, repetition period, and center frequency.

The intermediate frequency transmitting signal module receives the waveform parameters from the control module and configures the DDS to generate the required transmitting signal according to the waveform parameters.

As shown in fig. 4, the signal acquisition module is implemented by first receiving an intermediate frequency transmission signal through an SMA interface; secondly, performing band-pass sampling on the intermediate-frequency signal by using an ADC chip to form an intermediate-frequency digital signal; thirdly, the ADC chip transmits the digital signal to the FPGA through the LVDS interface; and finally, carrying out digital down-conversion on the intermediate frequency signal in the FPGA, multiplying the received intermediate frequency digital signal by two paths of orthogonal digital local oscillator signals, and obtaining IQ two paths of orthogonal baseband signals through a low-pass filter.

The implementation block diagram of the echo modulation module is shown in fig. 5 and is divided into a doppler modulation sub-module and a distance modulation sub-module.

IQ two-path signals of a baseband and the speed of a target are used as the input of a Doppler modulation submodule according to a formula f_dCalculating the Doppler frequency shift of the target at 2 v/lambda, and generating the frequency f by using a CORDIC algorithm_dThe sine and cosine digital signals and IQ two-path baseband signals are subjected to complex multiplication to obtain echo baseband signals containing Doppler frequency shift.

After the distance modulation submodule receives the distance of the current target, the time delay tau of the echo relative to the emission signal is calculated according to a formula 2R-tau c, wherein R is the distance of the target relative to the radar, and c is the speed of light. According to the AD sampling frequency f of the signal acquisition module_sDetermining the minimum time unit Δ τ as 1/f_sDelay the echo andand dividing and rounding the minimum time unit to obtain the number M of sampling points needing time delay of the echo, namely tau/delta tau. After receiving the echo baseband signal containing the Doppler frequency shift output by the Doppler modulation submodule, the echo baseband signal is buffered in a FIFO (first in first out), meanwhile, a counter starts to count from 0, and the echo baseband signal containing the distance delay is read out when the counter counts to M.

The baseband signal can be converted into an echo signal carrying target distance and speed information after sequentially passing through the Doppler modulation submodule and the distance modulation submodule.