阅读说明：本技术 线性调频连续波雷达收发干扰对消装置及其控制算法 (Linear frequency modulation continuous wave radar receiving and transmitting interference cancellation device and control algorithm thereof ) 是由 王青 何方敏 张雲硕 孟进 葛松虎 周亮 李毅 李伟 于 2020-03-27 设计创作，主要内容包括：本发明公开了一种线性调频连续波雷达收发干扰对消装置及其控制算法。该系统包括耦合器、射频开关、多抽头模拟滤波器、合成器、接收通道、ADC、数字信号处理单元与多通道DAC,其中耦合器用于提取发射信号样本；射频开关用于开关耦合器直通端与发射天线间的连接；多抽头模拟滤波器用于产生自干扰对消信号；合成器用于将对消信号与接收信号进行合成；接收通道用于对合成器输出信号进行放大,并与发射信号进行混频和滤波得到差拍信号；ADC用于将差拍信号数字化；数字信号处理单元用于产生模拟滤波器数字权值；多通道DAC用于将数字权值信号转换为模拟电压。本发明可大幅降低ADC采样速率的要求,简化自干扰对消电路设计,降低成本。(The invention discloses a linear frequency modulation continuous wave radar receiving and transmitting interference cancellation device and a control algorithm thereof. The system comprises a coupler, a radio frequency switch, a multi-tap analog filter, a synthesizer, a receiving channel, an ADC, a digital signal processing unit and a multi-channel DAC, wherein the coupler is used for extracting a transmitting signal sample; the radio frequency switch is used for switching the connection between the through end of the coupler and the transmitting antenna; the multi-tap analog filter is used for generating a self-interference cancellation signal; the synthesizer is used for synthesizing the cancellation signal and the receiving signal; the receiving channel is used for amplifying the output signal of the synthesizer, and carrying out frequency mixing and filtering on the output signal and the transmitting signal to obtain a beat signal; the ADC is used for digitizing the beat signal; the digital signal processing unit is used for generating a digital weight value of the analog filter; the multi-channel DAC is used for converting the digital weight signals into analog voltages. The invention can greatly reduce the requirement of ADC sampling rate, simplify the design of the self-interference cancellation circuit and reduce the cost.)

1. A linear frequency modulation continuous wave radar receiving and transmitting interference cancellation device is characterized by comprising a coupler, a radio frequency switch, a multi-tap analog filter, a synthesizer, an ADC module, a digital signal processing unit and a multi-channel DAC module;

the input end of the coupler is electrically connected with the transmitting end of the linear frequency modulation continuous wave radar receiving and transmitting unit and is used for acquiring a transmitting signal sample; the through output end of the filter is electrically connected with the input end of the radio frequency switch, and the coupling output end of the filter is electrically connected with the input end of the multi-tap analog filter;

the output end of the radio frequency switch is electrically connected with the input end of the transmitting antenna; the coupler is used for connecting or disconnecting the coupler through port and the input end of the transmitting antenna;

the output end of the multi-tap analog filter is electrically connected with one input end of the synthesizer and is used for generating a self-interference cancellation signal;

the other input end of the synthesizer is electrically connected with the output end of the receiving antenna, and the output end of the synthesizer is electrically connected with the input end of a receiving channel of the linear frequency modulation continuous wave radar receiving and transmitting unit, so that a cancellation signal and a receiving signal are synthesized, and self-interference cancellation is realized;

the other input end of the receiving channel receives a transmitting signal from a transmitting end of the linear frequency modulation continuous wave radar transceiving unit, and the output end of the receiving channel is electrically connected with the input end of the ADC module and is used for carrying out low-noise amplification on a synthesizer output signal and the transmitting signal and carrying out frequency mixing and low-pass filtering on the synthesizer output signal and the transmitting signal to obtain a beat signal;

the input end of the ADC module is electrically connected with the beat signal output end of the linear frequency modulation continuous wave radar receiving and transmitting unit and is used for digitizing beat signals; the output end of the digital signal processing unit is electrically connected with the input end of the digital signal processing unit;

the digital signal processing unit is used for generating a digital weight value of the multi-tap filter, and the output end of the digital signal processing unit is electrically connected with the input end of the multi-channel DAC module;

the multi-channel DAC module is used for converting the digital weight value into an analog voltage signal, and the output end of the multi-channel DAC module is electrically connected with a weight value port of the multi-tap analog filter.

2. The interference cancellation device for sending and receiving of chirp continuous wave radar according to claim 1, wherein the multi-tap analog filter includes N power dividers, N synthesizers, delay lines, and vector modulators, wherein input terminals of the N power dividers are electrically connected to coupling output terminals of the couplers, output terminals of the N power dividers are respectively electrically connected to the N delay lines, the other ends of the N delay lines are respectively electrically connected to input terminals of the vector modulators corresponding to the N paths, output terminals of the N vector modulators are electrically connected to N input terminals of the synthesizers, and output terminals of the N synthesizers are electrically connected to input terminals of the synthesizers.

3. The apparatus according to claim 1, wherein the vector modulator comprises an isolator, a quadrature mixer, an I-way weight resistor and a Q-way weight resistor, an input terminal of the isolator is electrically connected to an output terminal of the delay line, an output terminal of the isolator is connected to a local oscillator terminal of the quadrature mixer, an I-way intermediate frequency terminal of the quadrature mixer is connected to one end of the I-way weight resistor, a Q-way intermediate frequency terminal of the quadrature mixer is connected to one end of the Q-way weight resistor, a radio frequency terminal of the quadrature mixer is electrically connected to an input terminal of the synthesizer, and the other ends of the I-way weight resistor and the Q-way weight resistor are electrically connected to an output terminal of the DAC, respectively.

4. The control algorithm of the interference cancellation device for sending and receiving of chirp continuous wave radar according to claim 1, characterized by comprising the following steps:

s1, disconnecting the input signal of the transmitting antenna;

s2, adjusting the attenuation of the nth branch of the multi-tap analog filter to the minimum value and adjusting the phase to 0 degree, adjusting the attenuation of the other branches to the maximum value and adjusting the phase to 0 degree, where N is 1, N is the number of taps of the multi-tap analog, digitizing and storing the beat signal output by the chirp continuous wave radar transceiver as a reference signal;

s3, repeating the step S2 to obtain one or more periods of digital beat signals corresponding to the radio frequency reference signals of each branch of the multi-tap analog filter; intercepting one or more cycles of the digital beat signal and storing as a local reference signal;

s4, restoring the input signal of the transmitting antenna;

s5, taking the received beat signal as an expected signal, and simultaneously obtaining the weight value of the multi-tap analog filter by using the self-adaptive filtering algorithm on the local reference signal obtained in S3;

and S6, inputting the weight value of the multi-tap analog filter obtained in the S5 into the multi-tap analog filter to obtain a radio frequency cancellation signal, and synthesizing the radio frequency cancellation signal and a received radio frequency signal to realize interference cancellation.

Technical Field

The invention relates to the technical field of frequency modulation continuous wave radars, in particular to a linear frequency modulation continuous wave radar receiving and transmitting interference cancellation device and a control algorithm thereof.

Background

The linear frequency modulation continuous wave radar is widely applied to platforms of aviation, aerospace, automobiles and the like for distance measurement, height measurement and speed measurement. Because the sending and receiving of the chirp continuous wave radar are carried out simultaneously, the sending signal may leak to the receiver, causing the problem of receiving and sending interference.

The cancellation technology is an effective means for improving the receiving and transmitting isolation of the continuous wave radar at present, and the basic principle is that a coupler is adopted to extract a part of transmitting signals as reference signals, the reference signals pass through an analog filter to generate cancellation signals with the same amplitude and opposite phases with leaked interference signals, and the cancellation signals are input and received signals are subjected to vector synthesis to realize interference cancellation. The cancellation process is generally performed at radio frequency or intermediate frequency, and a method combining radio frequency cancellation and intermediate frequency cancellation can also be adopted. However, considering that the dynamic range of the low-noise amplifier and the ADC is limited, the cancellation at the radio frequency can greatly reduce the power of the low-noise amplifier signal entering the receiving channel so as to avoid saturation of the low-noise amplifier signal, and therefore, the low-noise amplifier and the cancellation method are more in line with the requirements of practical application.

The analog filter weight control circuit for generating the cancellation signal can be implemented by a digital circuit or an analog circuit. If the filter has a simple structure, such as a single-tap FIR filter, the structure of the analog weight control circuit is simple, the analog weight control circuit can be realized in engineering, and the cost and the volume can be generally accepted. However, when the number of taps of the filter is large, the number of weights increases accordingly, and the analog circuit is difficult to be miniaturized, and a digital circuit is required. The problem with digital circuits is that if the rf or if signal is sampled directly, the required ADC sampling rate may be too high to achieve low cost and miniaturization. In practice, the bandwidth of a chirp continuous wave radar signal is large and can reach hundreds of megahertz or even gigahertz, the requirement on the sampling rate required by direct sampling is too high, and the hardware cost is too high, so that a digital weight control circuit becomes complicated or even cannot be realized. In addition, the calculation of the weight of the analog filter is generally realized by using an adaptive filtering algorithm such as LMS, and the like, and the algorithm needs to lead out a signal from each filter branch as a reference signal. Therefore, assuming that the number of taps of the filter is N, N reference signals are required, which also requires N down-conversion and digitization circuits, which also increases the complexity and cost of the circuit.

Chinese patent application No. 201010532671.4 discloses a method for canceling medium frequency interference, but it cannot be used for canceling radio frequency transmit-receive interference. A radio frequency cancellation system and method (application number: 201611193306.9) for continuous wave radar discloses a method for calculating the weight of vector modulator by using transmitted radio frequency signal and received radio frequency signal, and mainly aims at a single-tap analog filter, but the method needs an independent error detection circuit to obtain intermediate frequency detection signal, so when the method is extended to a multi-tap analog filter, the circuit complexity is higher

Disclosure of Invention

The invention aims to provide a sex frequency modulation continuous wave radar receiving and transmitting interference cancellation device and a using method thereof aiming at the defects of the prior art, which can greatly reduce the requirement of ADC sampling rate, simplify circuit design and reduce cost.

The invention provides a linear frequency modulation continuous wave radar receiving and transmitting interference cancellation device which is characterized by comprising a coupler, a radio frequency switch, a multi-tap analog filter, a synthesizer, an ADC module, a digital signal processing unit and a multi-channel DAC module;

the input end of the coupler is electrically connected with the transmitting end of the linear frequency modulation continuous wave radar receiving and transmitting unit and is used for acquiring a transmitting signal sample; the through output end of the filter is electrically connected with the input end of the radio frequency switch, and the coupling output end of the filter is electrically connected with the input end of the multi-tap analog filter;

the output end of the radio frequency switch is electrically connected with the input end of the transmitting antenna; the coupler is used for connecting or disconnecting the coupler through port and the input end of the transmitting antenna;

the output end of the multi-tap analog filter is electrically connected with one input end of the synthesizer and is used for generating a self-interference cancellation signal;

the other input end of the synthesizer is electrically connected with the output end of the receiving antenna, and the output end of the synthesizer is electrically connected with the input end of a receiving channel of the linear frequency modulation continuous wave radar receiving and transmitting unit, so that a cancellation signal and a receiving signal are synthesized, and self-interference cancellation is realized;

the other input end of the receiving channel receives a transmitting signal from a transmitting end of the linear frequency modulation continuous wave radar transceiving unit, and the output end of the receiving channel is electrically connected with the input end of the ADC module and is used for carrying out low-noise amplification on a synthesizer output signal and the transmitting signal and carrying out frequency mixing and low-pass filtering on the synthesizer output signal and the transmitting signal to obtain a beat signal;

the input end of the ADC module is electrically connected with the beat signal output end of the linear frequency modulation continuous wave radar receiving and transmitting unit and is used for digitizing beat signals; the output end of the digital signal processing unit is electrically connected with the input end of the digital signal processing unit;

the digital signal processing unit is used for generating a digital weight value of the multi-tap filter, and the output end of the digital signal processing unit is electrically connected with the input end of the multi-channel DAC module;

the multi-channel DAC module is used for converting the digital weight value into an analog voltage signal, and the output end of the multi-channel DAC module is electrically connected with a weight value port of the multi-tap analog filter.

In the above technical solution, the multi-tap analog filter includes N power dividers, N synthesizers, a delay line and a vector modulator, wherein an input end of each of the N power dividers is electrically connected to a coupling output end of the coupler, output ends of the N power dividers are respectively electrically connected to the N delay lines, another end of each of the N delay lines is respectively electrically connected to an input end of a corresponding vector modulator of the N power dividers, an output end of each of the N vector modulators is electrically connected to N input ends of the N synthesizers, and an output end of each of the N synthesizers is electrically connected to an input end of the synthesizer.

In the above technical solution, the vector modulator includes an isolator, a quadrature mixer, an I-way weight resistor and a Q-way weight resistor, an input end of the isolator is electrically connected to an output end of the delay line, an output end of the isolator is connected to a local oscillation end of the quadrature mixer, an I-way intermediate frequency end of the quadrature mixer is connected to one end of the I-way weight resistor, a Q-way intermediate frequency end of the quadrature mixer is connected to one end of the Q-way weight resistor, a radio frequency end of the quadrature mixer is electrically connected to an input end of the synthesizer, and the other ends of the I-way weight resistor and the Q-way weight resistor are electrically connected to an output end of the DAC.

In the above technical solution, the control algorithm of the interference cancellation device for sending and receiving of chirped continuous wave radar is characterized by comprising the following steps:

s1, disconnecting the input signal of the transmitting antenna;

s2, adjusting the attenuation of the nth branch of the multi-tap analog filter to the minimum value and adjusting the phase to 0 degree, adjusting the attenuation of the other branches to the maximum value and adjusting the phase to 0 degree, where N is 1, N is the number of taps of the multi-tap analog, digitizing and storing the beat signal output by the chirp continuous wave radar transceiver as a reference signal;

s3, repeating the step S2 to obtain one or more periods of digital beat signals corresponding to the radio frequency reference signals of each branch of the multi-tap analog filter; intercepting one or more cycles of the digital beat signal and storing as a local reference signal;

s4, restoring the input signal of the transmitting antenna;

s5, taking the received beat signal as an expected signal, and simultaneously obtaining the weight value of the multi-tap analog filter by using the self-adaptive filtering algorithm on the local reference signal obtained in S3;

and S6, inputting the weight value of the multi-tap analog filter obtained in the S5 into the multi-tap analog filter to obtain a radio frequency cancellation signal, and synthesizing the radio frequency cancellation signal and a received radio frequency signal to realize interference cancellation.

Compared with the prior art, the invention has the beneficial effects that:

1. the required ADC sampling rate is low and no additional mixer circuits are required. Because the weights are calculated by using the beat signals of the transmitting signal and the receiving signal, the signal bandwidth is generally below several MHz, and therefore, the required ADC sampling rate is far lower than the traditional requirement of hundreds of MHz and even gigahertz. Also, since the circuitry for generating the beat signal is typically present in the radar receiver, no additional mixing circuitry is required to be dedicated to generating the beat signal.

2. The needed ADC number is small, and a down-conversion circuit is not needed. Since the beat reference signal can be obtained by using a mixer circuit in the receiver, only 1 ADC is needed. In the conventional method, the input radio frequency signal of each tap of the filter needs to be subjected to down-conversion links such as mixing, filtering, ADC conversion and the like, so that N +1 down-conversion links are needed, where N is the number of taps of the filter. Therefore, the circuit structure of the invention is simpler.

3. The digital signal processing hardware is low in requirement and can be shared with other signal processing hardware of the linear frequency modulation continuous wave radar. Due to the adoption of the low-speed ADC, the clock rate requirement on digital type number processing hardware, such as chips of an FPGA and the like, is reduced. In addition, other signal processing tasks of the chirp continuous wave radar, such as fast fourier transform, can use the same FPGA chip. Based on the two points, the invention can greatly reduce the hardware cost and the circuit volume.

Drawings

Fig. 1 is a block diagram of a chirp continuous wave radar self-interference cancellation system provided by the present invention.

Fig. 2 is a block diagram of an analog multi-tap filter circuit according to an embodiment of the present invention.

Fig. 3 is a block diagram of a circuit structure of a vector modulator in an embodiment of the present invention.

Fig. 4 is a block diagram of a circuit structure of a receiving channel in an embodiment of the present invention.

Fig. 5 is a block diagram of the digital signal processing module according to the embodiment of the present invention.

FIG. 6 is a schematic diagram of a periodic beat reference signal in an embodiment of the present invention.

Fig. 7 is a schematic diagram of a receiver canceling an output beat signal in an embodiment of the present invention.

Detailed Description

The invention will be further described in detail with reference to the following drawings and specific examples, which are not intended to limit the invention, but are for clear understanding.

As shown in fig. 1, the present invention provides a interference cancellation device for sending and receiving of chirped continuous wave radar, comprising:

the input of the radio frequency switch 102 is connected with the through port of the coupler 103 and is used for connecting or disconnecting the connection between the through port of the coupler 103 and the input end of the transmitting antenna 101;

the input end of the coupler 103 is connected with the transmitting signal, and the output end of the coupler is connected with the input end of the radio frequency switch 102 and used for acquiring a transmitting signal sample;

a multi-tap analog filter 104, the input end of which is connected with the coupling end of the coupler 103, and the output end of which is connected with an input port of the combiner 106, for generating a self-interference cancellation signal;

a synthesizer 106, another input port of which is connected to the output end of the receiving antenna 105, and an output end of which is connected to the input end of the receiving channel 107, for synthesizing the cancellation signal and the receiving signal to realize self-interference cancellation;

a receiving channel 107, one input end of which is connected with the output of the synthesizer 106, the other input end of which is connected with the transmitting signal, and the output end of which is connected with the input of the ADC108, and which is used for carrying out low noise amplification on the output signal of the synthesizer and the transmitting signal, and carrying out frequency mixing and low pass filtering on the output signal of the synthesizer and the transmitting signal to obtain a beat signal;

an ADC108, the input end of which is connected with the output end of the receiving channel 107, and the output end of which is connected with the digital signal processing unit and is used for digitizing the beat signal;

a digital signal processing unit 109, the input of which is connected to the output of the ADC108 and the output of which is connected to the input of the DAC110, for generating the digital weight of the multi-tap filter;

and the DAC110, the input of which is connected to the output of the digital signal processing unit 109, and the output of which is connected to the weight control port of the multi-tap analog filter 104, is used for converting the digital weight into an analog voltage signal.

In this embodiment, the rf switch is a single-pole double-throw rf switch, and the first output port of the rf switch is connected to the transmitting antenna and the second output port of the rf switch is connected to the 50-ohm matched load. When the rf switch is switched to the second output port, the connection between the through port of the coupler 103 and the transmitting antenna can be disconnected. The coupler 103 adopts a broadband bidirectional coupler, and the coupling degree is 10 dB. The coupling degree cannot be too large so as to reduce the insertion loss of the coupler to the transmission signal.

Fig. 2 is a block diagram of an embodiment of the multi-tap analog filter 104 according to the present invention. For convenience of description, the number of taps of the multi-tap analog filter is denoted by N. The multi-tap analog filter 104 includes: an input of the N-path power divider 201 is connected to the coupling end of the coupler 103, and an output thereof is connected to an input end of the delay line 202; a delay line 202, the output of which is connected with the input end of the vector modulator 203; a vector modulator 203, the output of which is connected to one input of the multiplexer 204; the output of the N-way synthesizer 204 is connected to an input of the synthesizer 106. Taking N as 2 as an example, the multi-tap analog filter 104 of the present embodiment includes 2 delay lines, 2 vector modulators, 1 2 output power dividers, and 1 2 input combiners. The delay line 1 and the delay line 2 have different delays, in this example, the delay line 2 delays D2 being D1+1/B, where D1 is the delay of the delay line 1, and B is the transmission signal bandwidth.

Fig. 3 is a block diagram of an embodiment of the vector modulator 203 of the present invention. The vector modulator 203 includes: an input end of the isolator 301 is electrically connected with an output end of the delay line 202, and an output end of the isolator is connected with a local oscillation end of the quadrature mixer 302; an I-path intermediate frequency end of the quadrature mixer 302 is connected with one end of an I-path weight value resistor 303, a Q-path intermediate frequency end is connected with one end of a Q-path weight value resistor 304, and a radio frequency end is electrically connected with one input end of the synthesizer 204; the other ends of the I-path weight resistor 303 and the Q-path weight resistor 304 are electrically connected with the output end of the multi-channel DAC108 respectively. The quadrature mixer 302 adopts a schottky diode double-balanced mixer-based quadrature mixer; the I-path weight resistor 303 and the Q-path weight resistor 304 are 360 ohms, so that the DAC output voltage (-5V to +5V) is divided to a working voltage suitable for the quadrature mixer, and the quadrature mixer 302 is protected to avoid burning due to an excessive input voltage at the intermediate frequency end.

Fig. 4 is a block diagram of an embodiment of the receiving channel 107 according to the present invention. The reception channel 107 includes: a low-noise amplifier module 401, the input end of which is connected to the output of the synthesizer 106, and the output end of which is connected to the radio frequency input end of the mixer 402, for amplifying the received signal; a mixer 402, the local oscillator input end of which is connected with the transmitting signal, and the output end of which is connected with the input end of the low-pass filter 403, for mixing the transmitting signal and the receiving signal to obtain a beat signal; a low-pass filter 404, the output of which is connected to the input of the low-noise amplifier 404 for filtering the spurious and harmonic in the output of the mixer 402; and the output end of the low-noise amplifier 404 is connected with the ADC108 and is used for amplifying the signal output by the low-pass filter 403 and driving a post-stage circuit.

In this embodiment, the ADC108 parameters: sample rate 5Msps, bit wide 16 bits. The DAC parameters are: the sampling rate is 500ksps, the bit width is 20bit, and the output voltage is-5V- +5V, so that a higher dynamic range and a lower spurious level are obtained, the vector modulator is matched, and the control voltage of the vector modulator is matched, so that the enough amplitude and phase adjusting range is ensured. The digital signal processing unit is realized by adopting an FPGA (field programmable gate array) so as to reduce the loop delay of the self-adaptive filtering algorithm.

In the invention, the digital signal processing unit can be used for executing other radar signal processing tasks at the same time. Fig. 5 is a block diagram of the signal processing modules in the digital signal processing unit 109 according to the present invention. The basic principle is as follows: the received signal is divided into two paths at the same time, wherein one path is provided for the adaptive filtering algorithm module 501, and the other path is provided for the radar signal processing module 503; the reference signal module 502 is configured to generate a local reference signal; the adaptive filtering module 501 takes the received signal and the local reference signal as input, and generates a digital weight signal to output; the radar signal processing module 503 generates information such as a target distance and outputs the information to the external device through the communication port.

The invention further provides a control algorithm of the linear frequency modulation continuous wave radar digital control radio frequency self-interference device, which comprises the following specific steps:

1. turning off the rf switch 102; adjusting the attenuation of the first branch of the multi-tap analog filter 104 to the minimum value and the phase to 0 degree, adjusting the attenuation of other branches to the maximum value and the phase to 0 degree, and taking the obtained digital beat signal as a reference signal; repeating the previous step to obtain one or more periods of digital beat signals corresponding to the radio frequency reference signals of each branch of the multi-tap analog filter; intercepting one or more cycles of the digital beat signal and storing as a local reference signal;

2. turning on the rf switch 102; taking the received beat signal as an expected signal, taking the digital beat signal stored in the step 1 as a reference signal, and obtaining a weight value of the multi-tap analog filter by using a self-adaptive filtering algorithm;

3. inputting the weight voltage to a multi-tap analog filter to obtain a radio frequency cancellation signal; and synthesizing the radio frequency cancellation signal and the received radio frequency signal to realize interference cancellation.

The basic principle is as follows:

1. in step 1, the rf switch is turned off to avoid the transmission signal coupling into the receiving channel through the antenna and affecting the local reference signal extraction. And adjusting the attenuation of the vector modulators in other taps to the maximum value, and independently obtaining the reference beat signal corresponding to a certain residual tap. Because the chirp continuous wave has periodicity and the time delay and amplitude of the reference signal are fixed, the beat signals of the reference signal and the transmitting signal are also periodic and fixed in amplitude. Therefore, for calculating the weight, only the beat signal of more than 1 period needs to be intercepted. Fig. 6 is a schematic diagram of the periodic beat signal. The same periodic signal can be obtained by intercepting the beat signal of 1 period and circularly playing.

2. In step 2, a common adaptive filtering algorithm such as an LMS (Least Mean Square) algorithm is used to calculate the weight. Fig. 7 shows a receiver beat signal obtained by this method. The self-interference cancellation process starts from time 0. After the cancellation algorithm is converged, beat signal components corresponding to the self-interference signals are suppressed, and a target echo signal waveform can be restored.

Details not described in this specification are within the skill of the art that are well known to those skilled in the art.