Radar system and radar signal processing method

Abstract

The present application relates to a radar system and a radar signal processing method, the radar system comprising: one or more transmitting channel devices, used to process a radar signal to be transmitted according to a first control parameter to generate a transmitting signal; one or more receiving channel devices, used to receive an echo signal of the transmitting signal, and process the received echo signal according to a second control parameter to obtain a receiving signal; a control processor, used to read and write the first control parameter and the second control parameter connected to a system bus, wherein the first control parameter and the second control parameter are preset in a storage medium of the radar system and / or set by the control processor. The present application relates to a radar system capable of defining parameters, capable of being compatible with various formats, such as compatible with FMCW radar, PMCW radar, and pulse radar, and capable of achieving the effect of being able to flexibly select a suitable technical system as needed.

Description

Technical Field

[0001] The present application relates to the technical field of radar signal processing, and in particular to a radar system and a radar signal processing method. Background Art

[0002] As an important sensor for realizing autonomous driving or assisted driving, vehicle-mounted radar is increasingly being installed in vehicles. Currently, most vehicle-mounted radar products on the market are continuous wave radars, among which the most mainstream technical solution is frequency modulated continuous wave (FMCW) radar. In recent years, phase modulated continuous wave (PMCW) radar has also become an important development trend of vehicle-mounted radar due to its unique advantages (high accuracy, strong anti-interference ability, etc.).

[0003] FMCW radar directly generates a frequency modulated signal through the voltage controlled oscillator (VCO) of the phase-locked loop, which is then multiplied and sent to the transmission channel for transmission, and mixed with the echo signal at the receiving end. The local oscillator of PMCW radar generates a single-frequency signal and multiplies it as a carrier frequency. The carrier frequency is modulated and transmitted by the phase coded signal generated by the phase modulator on the transmission channel, and mixed with the echo signal at the receiving end.

[0004] Because FMCW radar transmits frequency modulated signals (the frequency of the signal changes over time), in order to ensure the accuracy of radar measurement, strict requirements are imposed on frequency locking speed, frequency modulation linearity, power flatness, etc. The local oscillator of PMCW radar is a single-frequency signal and does not require frequency modulation, so it has lower requirements on RF link devices including frequency sources.

[0005] In the echo signal link, under the FMCW radar, after the echo signal is mixed, demodulated and low-pass filtered, the echo signals of targets at different distances correspond to different frequency points on the signal spectrum after mixing and filtering. The relationship between the frequency value and the distance of the target relative to the radar and the linear sweep slope of the transmitted signal is as follows:

[0006] Where R is the distance of the target relative to the radar, c is the speed of light, k is the frequency sweep slope, and F is the frequency value corresponding to the target at a distance of R. For example, when R=200m and k=30MHz / us, it can be concluded that F=4MHz. Generally speaking, the frequency value F is basically in the MHz level or below, so the FMCW radar can use an ADC (analog-to-digital converter) with a sampling rate of tens of MHz.

[0007] For PMCW radar, although the carrier frequency is removed after the target echo is mixed with the carrier local oscillator and low-pass filtered, the ADC sampling rate needs to cover the phase modulation rate, that is, the signal bandwidth. Therefore, the ADC sampling rate is generally required to be at least in the GHz range. Therefore, compared with FMCW radar, PMCW radar has higher requirements for the ADC sampling rate. At the same time, the increase in sampling rate will inevitably lead to an increase in power consumption. In order to balance this point, the ADC bit width in PMCW radar will be designed to be lower. The ADC bit width in FMCW radar chips is generally around 12 bits, while it may be only around 6 bits in PMCW radar chips.

[0008] After the ADC acquires the raw data, the PMCW standard uses the matched filtering method to extract the distance dimension information of the received echo, while the FMCW standard processes it based on the Fourier transform FFT. Combined with a specific coding method, it is easier for the radar to achieve simultaneous transmission of multiple antennas or multiple devices under the matched filter. Specifically, the PMCW standard can avoid mutual interference between antennas or devices by assigning orthogonal spread spectrum codes to different antennas or different devices. These are the advantages of PMCW radar in signal processing. But at the same time, the influence of Doppler phase shift on radar measurement accuracy is more obvious under the PMCW standard, and it is necessary to optimize the design of phase coding or add a Doppler compensation algorithm at the signal processing end.

[0009] In addition, the core advantage of PMCW radar over FMCW radar is its stronger anti-interference ability. The RF signal of FMCW radar requires a large bandwidth (the larger the bandwidth, the higher the distance resolution), while the available frequency band of vehicle-mounted radar is limited: 76-81GHz. Therefore, as the number of radars increases, the interference seen by radar will undoubtedly continue to worsen.

[0010] As two main technical routes in continuous wave radar, FMCW and PMCW radars each have their own advantages and disadvantages, and there are often problems that are difficult to balance in actual design.

[0011] In addition to continuous wave radar, pulse radar is also an important technical system in radar technology. Compared with continuous wave radar, pulse radar only keeps receiving without sending any signal most of the time, and only transmits a pulse signal with a very short duration in a small part of the time. Therefore, at the same peak transmit power, the total transmit energy of pulse radar is much smaller than that of continuous wave radar. However, pulse radar is more used in long-range radar detection scenarios (such as military scenarios), and its peak transmit power is several orders of magnitude higher than that of civilian scenarios. In this scenario, if the continuous wave radar system is still used, the transmitter will leak extremely high transmit power to the receiver, which may cause damage to the receiving circuit, and at the same time, it has extremely high requirements for the dynamic range of the received wave power. In contrast, pulse radar controls the transmission and reception through the transceiver switch component in time division to avoid receiving signals while transmitting signals, thereby avoiding the problem of transmit power leaking directly to the receiver.

[0012] In summary, both continuous wave radar and pulse radar are important technical standards in today's radar technology, among which continuous wave radar includes (but is not limited to) two subdivided standards: FMCW and PMCW. Different standards are suitable for different application scenarios and requirements, corresponding to different implementation solutions. Summary of the invention

[0013] In the prior art, different radar systems have different hardware implementations, and when a device (such as a vehicle) supports one system, it often cannot support another system. Different systems have their own advantages and disadvantages and are suitable for different application scenarios and needs. The present application relates to a radar system capable of defining parameters, which is compatible with various systems, such as FMCW radar, PMCW radar, and pulse radar, and can achieve the effect of being able to flexibly select the appropriate technical system as needed.

[0014] According to one aspect of the present application, a radar system is provided, characterized in that it includes: One or more transmission channel devices, used for processing the radar signal to be transmitted according to the first control parameter to generate a transmission signal; one or more receiving channel devices, configured to receive an echo signal of the transmitted signal and process the received echo signal according to a second control parameter to obtain a received signal; and A control processor is used to perform read and write control on the first control parameter and the second control parameter connected to a system bus, wherein the first control parameter and the second control parameter are preset in a storage medium of the radar system and / or are set by the control processor.

[0015] According to another aspect of the present application, a radar signal processing method is provided, characterized by comprising: Processing the radar signal to be transmitted according to the first control parameter by one or more transmission channel devices to generate a transmission signal; and Receiving an echo signal of the transmission signal through one or more receiving channel devices, and processing the received echo signal according to a second control parameter to obtain a receiving signal; The first control parameter and the second control parameter are preset in a storage medium of the radar system and / or are set by a control processor.

[0016] According to the radar system and radar signal processing method provided by the present application, the radar system implemented can simultaneously support different radar standards according to the respective characteristics of different radar standards, for example, it can simultaneously support three different radar standards of FMCW, PMCW, and pulse radar, and it can define the control parameters, pulse waveform, and receiving algorithm of the radar system. The radar system can process signals of different radar standards, making the radar system highly versatile. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without exceeding the scope of protection required by the present application.

[0018] Figure 1 It is a block diagram of the radar system.

[0019] Figure 2 According to an embodiment of the present application Figure 1 The structural diagram of the transmitting channel device in the radar system shown.

[0020] Figure 3 According to an embodiment of the present application Figure 1 The structural diagram of the receiving channel device in the radar system shown.

[0021] Figure 4 According to another embodiment of the present application Figure 1 The structural diagram of the receiving channel device in the radar system shown.

[0022] Figure 5 According to an embodiment of the present application Figure 4 The structural diagram of the dispersion compensation unit in the receiving channel device is shown.

[0023] Figure 6 It is a structural diagram of a digital up-conversion unit or a digital down-conversion unit according to an embodiment of the present application.

[0024] Figure 7 According to an embodiment of the present application Figure 4 The structural diagram of the correlator in the receiving channel device is shown.

[0025] Figure 8 It is a schematic diagram of code correlation under the PMCW standard according to an embodiment of the present application.

[0026] Fig. 9 It is a schematic diagram of a transmission signal under the FMCW system according to an embodiment of the present application.

[0027] Fig.10 It is a working flow chart of a radar system under PMCW and pulse radar formats according to an embodiment of the present application.

[0028] Fig.11 This is a working flow chart of a radar system under the FMCW format according to an embodiment of the present application.

[0029] Fig.12 is a flowchart of a radar signal processing method according to an embodiment of the present application. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0031] Figure 1 This is the block diagram of the radar system. Figure 1 As shown, the system includes a transmitting channel device, a receiving channel device and a control processor, wherein the number of the transmitting channel device and the receiving channel device can be one or more. Figure 1 As shown, the transmitting channel device includes TX1, TX2, ... TXm, and the receiving channel device includes RX1, RX2, ... RXn, where m, n≥1. The transmitting channel device, the receiving channel device and the control processor are interconnected through a bus. According to a specific embodiment, the control processor can be a CPU.

[0032] like Figure 1 As shown, the system also includes an XTAL (External Crystal Oscillator) module for generating a clock source. The clock output by the XTAL module is set to clk XTALOne of the XTAL output clocks is given to the RFPLL phase-locked loop module, which multiplies it to the RF local oscillator signal LO. For millimeter-wave radar applications, the clock frequency is usually between 76 and 81 GHz. The other XTAL output clock is given to the BBPLL phase-locked loop module, which multiplies the clk XTAL Frequency multiplication, output four clocks, respectively, DAC (Digital-to-Analog Converter, digital-to-analog converter) sampling clock clk DAC , ADC sampling clock clk ADC , baseband digital signal processing clock clk BB , and control processor clock clk CPU .

[0033] According to an embodiment, the application of millimeter wave radar can be taken as an example, and the LO frequency is set to be around 79 GHz and the signal bandwidth is 1 GHz. The frequencies of these clocks can be set according to the following parameters: F XTAL =38.4MHz F LO =79.104GHz F DAC =5990.4MHz F ADC =1996.8MHz F BB =998.4MHz F CPU =499.2MHz Under a given XTAL clock, the frequency multipliers of the multiple clocks output by the RFPLL and BBPLL relative to the XTAL clock can be adjusted as needed according to the carrier frequency and bandwidth of the radar signal and can be flexibly configured in a software-defined manner.

[0034] According to one embodiment, Figure 1 The radar system shown also includes a radar data co-processor. Figure 1 The radar system shown has a total of M transmitting channels and N receiving channels, which can form M×N virtual array elements to form an array antenna to achieve angle measurement, radar imaging and other capabilities. The control parameters of all transmitting channel devices are connected to the system bus through the register interface, and can be read and written by the control processor hanging on the bus. The control parameters of all receiving channel devices are also connected to the system bus through the register interface. At the same time, the data processed in the receiving channel is also connected to the system bus for direct reading by the radar data coprocessor through DMA (Direct Memory Access).

[0035] like Figure 1 As shown, the control processor is mounted on the bus and is responsible for the execution logic of the entire system. The control processor performs read and write control on each transmitting channel device and receiving channel device on the scale of a radar signal (e.g., 1us), so that most operations on the radar signal can be defined by the control processor, for example, by software inside the control processor.

[0036] exist Figure 1 In the illustrated embodiment, the radar data coprocessor is responsible for implementing the subsequent radar signal processing related algorithms for the raw data processed by the receiving channel device, including FFT in the slow time domain, FFT in the angle domain, matrix decomposition and other operations. The control register interface of the coprocessor is also connected to the system bus, and is read and written by the control processor. For the FMCW format, the raw data output by the receiving channel device is the frequency domain data after FFT of the sampled data; for the PMCW and pulse radar formats, the raw data output by the receiving channel device is the channel impulse response and signal after the relevant operations are performed on the sampled data. Under the three formats, the data transmission format of the signal is exactly the same, and all represent the echo information in the distance (or fast time) dimension.

[0037] Figure 2 According to an embodiment of the present application Figure 1 The structure diagram of the transmitting channel device in the radar system is shown in FIG. Figure 2 As shown, the transmission channel device includes a digital baseband transmission channel, a first DAC and an analog transmission channel, wherein the digital baseband transmission channel includes a first pseudo code generation unit, a first upsampling filter unit and a first digital up-conversion unit connected in sequence, and the digital baseband transmission channel is used to perform digital baseband processing on the radar signal to be transmitted to generate a digital signal; the first DAC is connected to the digital baseband transmission channel, and is used to convert the digital signal from the digital baseband transmission channel into an analog signal; the analog transmission channel is connected to the first DAC, and includes a first baseband filter, a first RF mixer, a power amplifier and an antenna unit connected in sequence, and the analog transmission channel is used to perform analog processing on the analog signal to generate a transmission signal.

[0038] In one embodiment, the structure of the digital up-conversion unit is as follows: Figure 6 As shown. Figure 6 In the multiplication of the input IQ complex signal and a complex carrier signal (consisting of the cosine real part and the sinine imaginary part), the real-time phase of the complex carrier signal is determined by three parameters: is the initial phase, F is the initial sweep frequency, which determines the amount of phase change each time. The sweep rate determines the amount of frequency change each time. These three parameters can also be configured by the control processor as part of the control parameters. The speed increases linearly, while the frequency sweep phase The frequency conversion is performed by increasing F each time. The corresponding cos and sin values ​​are calculated based on the real-time phase of the complex carrier signal, and the complex multiplication with the input signal is performed to complete the digital frequency conversion.

[0039] The output data of the digital up-conversion unit is sampled at a rate of F DAC The I / Q data is directly sent to two DACs for digital-to-analog conversion. The analog signals converted by DAC are then sent to the I / Q analog processing units, and after passing through the first baseband filter, the first RF mixer, and the power amplifier, they are sent to the antenna unit for transmission into space.

[0040] For the transmission channel device, the corresponding control parameters can be determined so that the transmission channel device can process the radar signal to be transmitted according to the corresponding control parameters to generate a transmission signal. According to one embodiment, the control parameters corresponding to the transmission channel device can be preset in the storage medium of the radar system or set by the control processor. The control parameters corresponding to the transmission channel device may include the sweep bandwidth B, the frequency increase value , the length P of a radar signal, the transmission power, etc., and for different radar standards, the control parameters can instruct the units or devices in the transmission channel device to perform different processing.

[0041] According to a specific embodiment, in the FMCW system, since the transmission waveform does not involve a pseudo code, the control parameter can instruct the first pseudo code generation unit to output an all-1 chip symbol, or a rectangular window can be added to the all-1 signal to form a square wave with a certain duty cycle, which is equivalent to not performing phase modulation on the baseband signal. The output chip symbol is input to the first upsampling filter unit, and the control parameter instructs the first upsampling filter unit to use an all-1 rectangular window filter, and the sampling rate is increased to F DAC , the filtered baseband signal can still be an all-1 signal or a square wave with a certain duty cycle. At the same time, the control parameter instructs the first digital up-conversion unit to perform a [-B / 2, B / 2] sweep frequency processing on the radar signal to be transmitted, and after the DAC, it is converted into an analog continuous signal and output to the transmitting RF module. The baseband analog output signal of a single radar signal can be expressed as:

[0042] in is the non-zero duration of a single radar signal, During this time, the frequency of the baseband transmission signal output by the DAC increases linearly from -B / 2 to B / 2 over time, completing a linear frequency sweep with a bandwidth of B. represents the radar signal period, for have , the duty cycle of the generated FMCW signal is ,like Fig. 9 In particular, if , the signal duty cycle is 1.

[0043] according to Figure 6 The digital up-conversion or digital down-conversion unit shown in the figure controls the frequency sweep rate of the processor. , initial sweep frequency F and initial phase To configure. Sweep frequency F press The speed increases linearly, while the frequency sweep phase According to the rule of increasing F each time. For example, in the above formula given In the waveform, the control processor configures the parameters for the digital up-conversion unit as follows: =k,F=-B / 2, =0.

[0044] According to another specific embodiment, in the PMCW or pulse radar format, the pseudo code generation unit generates a chip sequence with excellent autocorrelation characteristics. For ease of implementation, the chip sequence can be composed of ±1, that is, a sequence of 0° / 180° phase modulation. Similar to FMCW, the generated PMCW chip sequence may also have a certain duty cycle, that is, a portion of the time is a ±1 chip symbol, and the remaining time is a 0 chip symbol. The control parameter can instruct the first pseudo code generation unit to generate a chip sequence with low sidelobe autocorrelation characteristics, and the first upsampling filter unit performs a convolution operation on the chip sequence to form a baseband digital waveform; since the PMCW or pulse radar wave signal does not require baseband frequency conversion, the first digital up-conversion unit maintains a fixed frequency, does not perform frequency sweeping, and does not process the radar signal to be transmitted (PMCW or pulse radar wave signal). Then, it passes through the DAC to become an analog signal output to the RF module. The output signal corresponding to a single radar signal can be expressed as: , Where K represents the number of chips in the chip sequence, is the duration of a single chip, ∈{±1} represents the i-th chip symbol, and p(t) is the transmitted pulse waveform. Among them, p(t) determines the bandwidth of the transmitted signal, and its specific selection can be controlled by the control processor.

[0045] In one embodiment, in order to reduce the complexity of hardware implementation, the pseudo code generation units of all transmission channel devices can share one pseudo code generation unit, that is, all transmission channels use the same pseudo code. When multiple transmission channel devices are turned on at the same time, the pseudo code generation unit of each transmission channel superimposes a Walsh code of each channel on the shared pseudo code. In addition, the NCO (Numerically Controlled Oscillator) in the digital up-conversion unit can also be shared among various transmission channels.

[0046] For different radar systems, multiple transmission channel devices can start signal transmission in sequence in a time-division manner, or can be started at the same time to transmit signals. When multiple transmission channel devices are started at the same time, it is usually necessary to superimpose the respective Walsh codes on the transmission channels to ensure the orthogonality of the signals between the transmission channels.

[0047] When multiple transmission channel devices are turned on at the same time, the control parameter can instruct the first pseudo code generation unit of each transmission channel to superimpose a Walsh code of each transmission channel on the generated pseudo code. According to one embodiment, the length of the Walsh code is different depending on the number of transmission channels supported. For the number of transmission channels M, the length of the Walsh code is .

[0048] In one embodiment, the generated PMCW radar signal is allowed to repeat L times so that the receiving channel can accumulate the received radar signal to improve the signal-to-noise ratio. In the case where multiple transmitting channel devices are turned on at the same time to transmit signals, after adding the Walsh code, the generated transmitting radar signal is as follows: Figure 8 As shown in the figure, the secondary code is the Walsh code. For the transmitted signal under a single Walsh code element, its general form is a single radar signal After L repetitions, zero padding is performed, and the total number of chips included is recorded as P, and the number of zero-padded chips is P-KL. The transmission signal after repetition and zero padding is multiplied by +1 or -1 according to the polarity of the Walsh code, thereby completing the generation of the transmission signal under a single Walsh code element. The transmission channel can generate the transmission signal under subsequent Walsh code elements in the same way according to the Walsh code length. In particular, L can be 1, which means that only one radar signal is contained under a single Walsh code element.

[0049] In the pulse radar system, the processing flow of the transmitted signal is the same as that of the PMCW radar. The baseband analog signal output by the DAC of a single radar signal can also be expressed as: .

[0050] The main difference between pulse radar and PMCW radar is that for pulse radar, K is usually smaller and L=1, and the duration of non-zero code chip K is It is much smaller than the radar signal period, so that the transmit signal is 0 for most of the time, and the duty cycle is very small. In this way, the radar transmit channel and the receive channel can be alternated in a time-division manner to avoid the transmit signal from leaking directly to the receiver input. In contrast, for PMCW radar, the duration of the non-zero code chip is comparable to or even equal to the radar signal period, and the duty cycle of the transmit signal is large.

[0051] In the case of multiple transmitting antennas, in order to avoid interference between different transmitting antennas, different transmitting channel devices can transmit signals in a time-division manner, or, as mentioned above, different transmitting channel devices can be modulated with Walsh codes so that the transmit signals of different antennas can be transmitted simultaneously. Here is an example of Walsh code division transmission of two transmitting channel devices (corresponding to two transmitting antennas). For simplicity, it is assumed here that L=1 and there is no zero padding operation. Consider the case of two antennas, and the signals of two radar signal cycles are transmitted continuously at the same time. The first antenna sends x(t) in both radar signal cycles; the second antenna sends x(t) in the first radar signal cycle and -x(t) in the second radar signal cycle, thereby achieving code division orthogonality of length 2. The Walsh code corresponding to the first antenna is [1,1], and the second antenna corresponds to [1,-1]. The above example can be easily extended to the case of multiple transmitting antennas: for the case of M transmitting antennas, a length of Walsh codes are used to ensure that the code sequences assigned to different transmit antennas are orthogonal. Therefore, all M transmit antennas need to send a total of The radar signal x(t) can be a transmission symbol of FMCW, PMCW or pulse radar.

[0052] According to an embodiment, when a plurality of transmission channel devices start signal transmission in sequence in a time division manner, the NCO in the first digital up-conversion unit may be shared among the transmission channels.

[0053] Figure 3 According to an embodiment of the present application Figure 1 The structure diagram of the receiving channel device in the radar system is shown in FIG. Figure 3As shown, the receiving channel device includes an analog receiving channel, an ADC and a digital baseband receiving channel, wherein the analog receiving channel includes a low noise amplifier, a second radio frequency mixer and a second baseband filter connected in sequence, and the analog receiving channel is used to perform analog processing on the received echo signal to generate an analog receiving signal; the ADC is connected to the analog receiving channel and is used to convert the analog receiving signal from the analog receiving channel into a digital receiving signal; the digital baseband receiving channel is connected to the ADC and includes an energy detection unit, a digital down-conversion unit, a correlator and an accumulator connected in sequence, and the digital baseband receiving channel is used to perform digital baseband processing on the digital receiving signal to generate a receiving signal. In the receiving channel device, the receiving signal becomes a baseband digital signal after amplification, mixing and ADC sampling. In the digital processing part, the digital signal first passes through the energy detection module to detect the saturation of the ADC output. If there are too many saturated sampling points, the receiving gain should be appropriately reduced; otherwise, the receiving gain can be appropriately increased.

[0054] In order to solve the influence of the direct part of the transmitted signal on the receiving channel in radar applications, an independent interference elimination signal module can be set in the receiving channel device. Figure 4 According to another embodiment of the present application Figure 1 The structure diagram of the receiving channel device in the radar system shown in FIG. Figure 3 compared to, Figure 4 The receiving channel device shown includes not only an analog receiving channel, an ADC and a digital baseband receiving channel, but also an interference elimination signal module and a coupler TO. Figure 4 As shown, the interference elimination signal module includes a second pseudo code generation unit, a second upsampling filtering unit, a second digital up-conversion unit, a dispersion compensation unit, a second DAC, a third baseband filter, a third RF mixer and an attenuator ATT which are connected in sequence, and the interference elimination signal module is used to generate an interference elimination signal; the coupler is connected to the interference elimination signal module and the analog receiving channel, and is used to couple the interference elimination signal with the received echo signal in an anti-phase manner.

[0055] In the interference cancellation signal module of the receiving channel device, it is first necessary to reconstruct the baseband signal transmitted by the transmitting channel device, which includes pseudo code generation, upsampling filtering and digital up-conversion. Among them, the pseudo code generation, upsampling filtering and digital up-conversion process are the same as the signal transmission process. Therefore, as an alternative, the digital signal before the DAC generated by the transmitting channel device can also be directly introduced into the receiving channel device. In order to simulate the delay and dispersion effects of the direct path from the transmitting antenna to the receiving antenna, the baseband digital signal should also pass through a dispersion compensation unit, which is essentially a FIR (Finite Impulse Response, finite impulse response) filter, so that the delay of the transmitting channel can also be compensated.

[0056] The function of the interference elimination signal module is equivalent to the signal synthesis of all the transmission channels. The signal generated by this unit is subtracted from the actual received signal at the analog RF end of the receiving channel, and then sent to the subsequent circuit of the analog receiving channel. The analog receiving channel amplifies, down-converts, and filters the signal, and then sends it to the ADC, which samples the analog signal at a sampling rate of F. ADC The signal is converted into a digital signal and sent to the digital baseband receiving channel, which performs energy detection on the signal and then sends it to the digital down-conversion unit.

[0057] For the receiving channel device, corresponding control parameters can be determined so that the receiving channel device can process the received signal according to the corresponding control parameters to generate a received signal. According to one embodiment, the control parameters corresponding to the receiving channel device can be preset in the storage medium of the radar system or set by the control processor. The control parameters corresponding to the receiving channel device may include the sweep bandwidth B, the frequency increase value , the length P of a radar signal, the receiving gain, etc., and for different radar formats, the control parameters can instruct the units or devices in the receiving channel device to perform different processing. According to a specific embodiment, in the FMCW format, the control parameters instruct the digital down-conversion unit to perform a frequency sweep in the same frequency range [-B / 2, B / 2] as the transmitting channel device, and the start time of the frequency sweep is controlled by the control processor according to the subsequent algorithm to ensure that the start time of the frequency sweep is synchronized with the time when the transmitting signal arrives at the receiving channel.

[0058] For FMCW radar system, the input signal is first processed by the digital down-conversion NCO to perform difference frequency processing on the digital received signal. The phase of the complex carrier signal generated by the NCO is opposite to the phase of the digital up-conversion NCO of the transmitting channel, thereby achieving the difference frequency effect. Since the echoes of scatterers at different distances appear as difference frequency signals of different frequencies after the difference frequency processing, in order to extract the frequency of the difference frequency signal, the signal should be subsequently subjected to FFT operation. The FFT operation here is performed with the help of the FFT unit in the correlator, such as Figure 7 As shown. Finally, after the FFT operation is completed, the same FFT signal enters the multi-channel accumulator for coherent accumulation to obtain the echo signal of each transmission channel to the current receiving channel. In the case where the transmission channel device superimposes the Walsh code, after the FFT operation is completed, the same FFT signal enters the multi-channel accumulator for coherent accumulation according to the Walsh code polarity of different transmission channels to obtain the echo signal of each transmission channel to the current receiving channel. Among them, the number of accumulators is equal to the number of channels.

[0059] According to a specific embodiment, in the PMCW or pulse radar system, the control parameter instructs the digital down-conversion unit to directly use a fixed frequency that is the same as the transmitting end to perform a frequency conversion operation.

[0060] For PMCW or pulse radar, the digital down-conversion NCO does not need to work and does not perform phase rotation on the baseband received signal. Afterwards, the signal enters the correlator and completes the correlation operation with the local code, where the local code is the pseudo code sequence used by a single radar signal. The specific implementation of the correlator is as follows: Figure 7 As shown in the figure, the basic principle is to use the equivalence of the circular convolution operation in the time domain and the multiplication operation in the frequency domain, and then transform the frequency domain signal back to the time domain after completing the multiplication operation in the frequency domain. Therefore, the input signal is first transformed to the frequency domain by the FFT module, and the product operation is performed with the FFT result of the time-reversed local code in the frequency domain, where the purpose of time-reversing the local code is to convert the circular convolution into a circular correlation operation. Finally, the frequency domain product result is transformed back to the time domain via IFFT and input into the subsequent accumulator to complete the accumulation. Among them, when the transmission channel device superimposes the Walsh code, the accumulator completes the accumulation according to the polarity of the Walsh code of different channels.

[0061] The signal after digital down conversion is sent to the correlator for correlation or FFT operation, such as Figure 7 As shown. In the PMCW or pulse radar system, for each receiving channel correlator, it is necessary to process M transmission signals. In the case where the M transmission signals all use the same pseudo code sequence, a correlation module can be used in the correlator, which uses the FFT fast algorithm:

[0062] in, It is represented as the conjugate of the FFT result of the time-reversal code sequence, which can be generated in advance by the control processor and stored in the correlator, and does not need to be calculated in real time; The received signal represents the FFT result of the received signal. After each set of input signals is sent to the correlator, an FFT operation is first performed on it. In the FMCW format, the operation result is directly handed over to the radar data coprocessor through DMA for subsequent operation; if it is a PMCW or pulse radar format, the result is combined with the locally stored Perform point-to-point multiplication and then do an IFFT to get a correlation result of the radar signal.

[0063] The FFT results or correlation results obtained by the above operations are then sent to the subsequent M-way accumulators for accumulation on the secondary code. When the Walsh code is superimposed on the transmission channel, each accumulator can configure the Walsh code of each symbol through control parameters (for example, through the control processor) when accumulating each symbol. The accumulator uses the symbol of the Walsh code to multiply the input signal before accumulation to distinguish different transmission channels. The results of the accumulator can be sent to the radar data coprocessor through DMA for subsequent processing.

[0064] In the case where the Walsh code is superimposed on the transmission channel, the dispersion compensation unit in the interference elimination signal module includes a Walsh flip subunit and an FIR filter, such as Figure 5 The Walsh flip subunit corresponds to the transmitting channel device one by one, and is used to perform a Walsh flip operation on the signal from the second digital up-conversion unit under the instruction of the control parameter corresponding to the receiving channel device to generate a Walsh flip signal, and the FIR filter is connected to the Walsh flip subunit to process the Walsh flip signal to generate a delay compensation signal.

[0065] Each receiving channel needs to eliminate the superimposed signals of multiple transmitting channels. Therefore, the dispersion compensation unit needs to perform a flip operation on the pseudo code data with the same Walsh code as each transmission, and then pass through the FIR filter to restore the dispersion and delay effects of each transmitting channel, and finally sum it before sending it to the DAC. The coefficients used by the FIR are calculated and configured by the processor. Since the dispersion effect and delay of the self-interference signals of different transmitting channels are different, the FIR coefficients should be obtained by multiplying the dispersion delay coefficients of the self-interference of each transmitting channel by the Walsh code polarity of each channel and then superimposing them. In actual implementation, the dispersion delay coefficients of the self-interference of each transmitting channel can be obtained by the control processor according to the size of the self-interference signal in the echo of each transmitting channel, using the LMS (Least Mean Squares) algorithm for iterative calculation. The baseband digital signal after dispersion compensation is converted into an analog signal by the DAC, and then used as the RF self-interference signal after orthogonal up-conversion and attenuation. This signal is anti-coupled with the echo signal to achieve the purpose of self-interference elimination. The attenuation value of the attenuator is controlled by the processor, which has the effect of coarsely adjusting the energy of the self-interference signal. At the same time, the fine adjustment of the self-interference signal of each transmission channel can be achieved by adjusting the FIR coefficient amplitude.

[0066] Fig.10 This is a radar system workflow diagram under PMCW and pulse radar formats according to an embodiment of the present application. Fig.10 In the embodiment shown, the transmission of multiple transmission channels is ensured to be orthogonal by Walsh codes. Before starting to transmit and receive, the transmission and reception parameters should be configured first, including the pseudo code length K in the radar signal, the radar signal length P, the pseudo code sequence c used, the Walsh code of each transmission channel, and the transmission and reception channel gain and other parameters. After completing the parameter configuration, the transmission and reception processing can be started. M transmission channels are turned on at the same time, and the transmission and reception are completed in the manner described above. The radar signal is transmitted under Walsh code element modulation, and the corresponding waveform is as follows Figure 8As shown in the figure, the secondary code is the Walsh code. N receiving channels are turned on at the same time as the transmitting channel. First, the dispersion compensation FIR filter coefficients used for self-interference elimination are estimated. The implementation method is to feedback control the dispersion compensation filter parameters according to the size of the self-interference signal in the accumulator result until the self-interference signal is eliminated to the minimum. After completing this step, the N receiving channels can actually receive the signal frame and output the echo results that can be used for target detection or regional imaging. Among them, for the pulse radar system, the self-interference elimination function can also be turned off, and self-interference can be avoided by turning on the transmission and reception in time.

[0067] Fig.11 FIG. 1 is a flowchart of a radar system under the FMCW standard according to an embodiment of the present application. Fig.11 In the embodiment shown, the transmission of multiple transmission channels is ensured to be orthogonal by time division. Before starting to transmit and receive, the transmission and reception parameters should be configured first, including parameters such as the sweep frequency range B, the frequency change speed Δf, the radar signal length P, and the transmission and reception channel gain. Each transmission channel is turned on in turn in a time division manner, and when each transmission channel is turned on, the N receiving channels are turned on at the same time. First, the dispersion compensation FIR filter coefficient for self-interference elimination is estimated, and the implementation method is to feedback control the dispersion compensation FIR filter coefficient according to the size of the self-interference signal in the FFT result until the self-interference signal is eliminated to the minimum. After completing this step, the N receiving channels can actually receive the signal frame and output the echo results that can be used for target detection or regional imaging.

[0068] It should be pointed out that the PMCW or pulse radar system can also open multiple transmission channels in a time-division manner, and the activation method of each transmission and reception channel is the same as the FMCW radar transmission and reception process described above, which will not be repeated here. Similarly, the FMCW radar system can also open multiple transmission channels at the same time by adding Walsh codes, and the corresponding transmission and reception channel activation method is the same as the PMCW or pulse radar transmission and reception process described above.

[0069] On the basis of the above embodiments, according to one aspect of the present application, a radar signal processing method is provided. Fig.12 FIG. 1 is a flow chart of a radar signal processing method according to an embodiment of the present application. Fig.12 As shown, the method comprises the following steps: Step S1201, processing the radar signal to be transmitted according to the first control parameter by one or more transmission channel devices to generate a transmission signal; and Step S1202, receiving an echo signal of the transmission signal through one or more receiving channel devices, and processing the received echo signal according to a second control parameter to obtain a received signal; The first control parameter and the second control parameter are preset in a storage medium of the radar system and / or are set by a control processor.

[0070] In some optional embodiments, step S1201 may include: In the FMCW radar system, according to the first control parameter, the first pseudo code generation unit is instructed to output an all-1 chip sequence, the first up-sampling filter unit uses an all-1 rectangular window filter, and the first digital up-conversion unit performs a sweep frequency processing of a preset sweep frequency bandwidth on the radar signal to be transmitted; and Under the PMCW or pulse radar standard, according to the first control parameter, the first pseudo code generating unit is instructed to generate a code chip sequence with a low sidelobe autocorrelation characteristic, the first upsampling filtering unit performs a convolution operation of the code chip sequence, and the first digital up-conversion unit does not process the radar signal to be transmitted.

[0071] In some optional embodiments, when there are multiple transmitting channel devices and they are turned on at the same time, step S1201 may include: According to the first control parameter, the first pseudo code generating unit is instructed to output a chip sequence and to superimpose a corresponding Walsh code on the output chip sequence.

[0072] In some optional embodiments, step S1202 may include: In the FMCW radar system, according to the second control parameter, instructing the digital down-conversion unit to perform difference frequency processing on the digital received signal; and In the PMCW or pulse radar standard, the digital down-conversion unit is instructed not to process the digital received signal according to the second control parameter.

[0073] In some optional embodiments, step S1202 may include: According to the second control parameter, the accumulator is instructed to multiply the sign of the Walsh code with the signal input to the accumulator before accumulation, so as to distinguish different transmission channels.

[0074] According to the radar system and radar signal processing method provided by the present application, the radar system implemented can support different radar standards at the same time according to the respective characteristics of different standard radars, for example, it can support three different radar standards of FMCW, PMCW and pulse radar at the same time, and it can define the control parameters, pulse waveform and receiving algorithm of the radar system, etc. The radar system can process signals of different radar standards, allowing flexible switching according to the actual application scenario, so that the radar system has extremely high versatility. In addition, the present application supports multi-transmit and multi-receive channel processing, and ensures the orthogonality between the transmission channels, so it supports the use of large-scale antenna arrays for high-resolution imaging. In addition, the present application supports self-interference elimination, which can significantly improve the dynamic range of the receiver input signal.

[0075] The embodiments of the present application are described in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method and its core idea of ​​the present application. At the same time, changes or deformations made by those skilled in the art based on the ideas of the present application, the specific implementation methods and the scope of application of the present application, all belong to the scope of protection of the present application. In summary, the content of this specification should not be construed as a limitation on the present application.

Claims

1. A radar system, characterized in that: include: One or more transmission channel devices, used for processing the radar signal to be transmitted according to the first control parameter to generate a transmission signal; One or more receiving channel devices, used for receiving the echo signal of the transmission signal, and processing the received echo signal according to the second control parameter to obtain a receiving signal; as well as A control processor is used to perform read and write control on the first control parameter and the second control parameter connected to a system bus, wherein the first control parameter and the second control parameter are preset in a storage medium of the radar system and / or are set by the control processor.

2. The radar system according to claim 1, characterized in that Each of the transmitting channel devices comprises: A digital baseband transmission channel, comprising a first pseudo code generation unit, a first up-sampling filter unit and a first digital up-conversion unit connected in sequence, wherein the digital baseband transmission channel is used to perform digital baseband processing on the radar signal to be transmitted to generate a digital signal; A first DAC, connected to the digital baseband transmission channel, for converting the digital signal from the digital baseband transmission channel into an analog signal; An analog transmission channel is connected to the first DAC, and includes a first baseband filter, a first RF mixer, a power amplifier and an antenna unit connected in sequence. The analog transmission channel is used to perform analog processing on the analog signal to generate the transmission signal.

3. The radar system according to claim 2, characterized in that Each of the receiving channel devices comprises: an analog receiving channel, comprising a low noise amplifier, a second radio frequency mixer and a second baseband filter connected in sequence, the analog receiving channel being used to perform analog processing on the received echo signal to generate an analog receiving signal; ADC, connected to the analog receiving channel, and used to convert the analog receiving signal from the analog receiving channel into a digital receiving signal; A digital baseband receiving channel is connected to the ADC, and includes an energy detection unit, a digital down-conversion unit, a correlator and an accumulator connected in sequence. The digital baseband receiving channel is used to perform digital baseband processing on the digital receiving signal to generate the receiving signal.

4. The radar system according to claim 3, characterized in that Each of the receiving channel devices further comprises: An interference cancellation signal module, comprising a second pseudo code generation unit, a second up-sampling filter unit, a second digital up-conversion unit, a dispersion compensation unit, a second DAC, a third baseband filter, a third radio frequency mixer and an attenuator connected in sequence, wherein the interference cancellation signal module is used to generate an interference cancellation signal; A coupler is connected to the interference elimination signal module and the analog receiving channel, and is used to perform anti-phase coupling between the interference elimination signal and the received echo signal.

5. The radar system according to claim 4, characterized in that The dispersion compensation unit comprises: a Walsh flip subunit, which corresponds to the transmission channel device one by one, and is used to perform a Walsh flip operation on the signal from the second digital up-conversion unit under the instruction of the second control parameter to generate a Walsh flip signal; and The FIR filter is connected to the Walsh flip subunit and is used for processing the Walsh flip signal to generate a delay compensation signal.

6. The radar system according to any one of claims 1 to 5, characterized in that: Also includes: The radar data coprocessor is connected to the one or more receiving channel devices and is used to perform radar signal processing on the received signal to generate radar echo information.

7. The radar system according to claim 3, characterized in that: In the FMCW radar system, the digital down-conversion unit performs difference frequency processing on the digital received signal under the instruction of the second control parameter; In the PMCW or pulse radar standard, the digital down-conversion unit does not process the digital received signal under the instruction of the second control parameter.

8. The radar system according to claim 3, characterized in that: In the FMCW radar system, according to the first control parameter, the first pseudo code generation unit outputs an all-1 chip sequence, the first up-sampling filter unit adopts an all-1 rectangular window filter, and the first digital up-conversion unit performs frequency conversion processing of a preset sweep bandwidth on the radar signal to be transmitted; Under the PMCW or pulse radar standard, according to the first control parameter, the first pseudo code generation unit generates a code chip sequence with a low sidelobe autocorrelation characteristic, the first upsampling filtering unit performs a convolution operation of the code chip sequence, and the first digital up-conversion unit does not process the radar signal to be transmitted.

9. The radar system according to claim 8, characterized in that: In the case that there are multiple transmitting channel devices and they are turned on simultaneously, the first pseudo code generating unit is used to output a chip sequence and superimpose a corresponding Walsh code on the output chip sequence under the instruction of the first control parameter.

10. The radar system according to claim 9, characterized in that: The accumulator is used to, under the instruction of the second control parameter, multiply the sign of the Walsh code with the signal input to the accumulator before accumulation to distinguish different transmission channels.

11. A radar signal processing method, characterized in that: include: Processing the radar signal to be transmitted according to the first control parameter by one or more transmission channel devices to generate a transmission signal; as well as Receiving an echo signal of the transmission signal through one or more receiving channel devices, and processing the received echo signal according to a second control parameter to obtain a receiving signal; The first control parameter and the second control parameter are preset in a storage medium of the radar system and / or are set by a control processor.

12. The method according to claim 11, characterized in that Each of the transmitting channel devices comprises: A digital baseband transmission channel, comprising a first pseudo code generation unit, a first up-sampling filter unit and a first digital up-conversion unit connected in sequence, wherein the digital baseband transmission channel is used to perform digital baseband processing on the radar signal to be transmitted to generate a digital signal; A first DAC, connected to the digital baseband transmission channel, for converting the digital signal from the digital baseband transmission channel into an analog signal; An analog transmission channel is connected to the first DAC, and includes a first baseband filter, a first RF mixer, a power amplifier and an antenna unit connected in sequence. The analog transmission channel is used to perform analog processing on the analog signal to generate the transmission signal.

13. The method according to claim 12, characterized in that The processing of the radar signal to be transmitted according to the first control parameter by one or more transmission channel devices includes: In the FMCW radar system, according to the first control parameter, the first pseudo code generation unit is instructed to output an all-1 chip sequence, the first up-sampling filter unit uses an all-1 rectangular window filter, and the first digital up-conversion unit performs frequency conversion processing of a preset sweep bandwidth on the radar signal to be transmitted; and Under the PMCW or pulse radar standard, according to the first control parameter, the first pseudo code generating unit is instructed to generate a code chip sequence with a low sidelobe autocorrelation characteristic, the first upsampling filtering unit performs a convolution operation of the code chip sequence, and the first digital up-conversion unit does not process the radar signal to be transmitted.

14. The method according to claim 11, characterized in that Each of the receiving channel devices comprises: an analog receiving channel, comprising a low noise amplifier, a second radio frequency mixer and a second baseband filter connected in sequence, the analog receiving channel being used to perform analog processing on the received echo signal to generate an analog receiving signal; ADC, connected to the analog receiving channel, and used to convert the analog receiving signal from the analog receiving channel into a digital receiving signal; A digital baseband receiving channel is connected to the ADC, and includes an energy detection unit, a digital down-conversion unit, a correlator and an accumulator connected in sequence. The digital baseband receiving channel is used to perform digital baseband processing on the digital receiving signal to generate the receiving signal.

15. The method according to claim 14, characterized in that The step of processing the received echo signal according to the second control parameter by one or more receiving channel devices comprises: In the FMCW radar system, according to the second control parameter, instructing the digital down-conversion unit to perform difference frequency processing on the digital received signal; and In the PMCW or pulse radar standard, the digital down-conversion unit is instructed not to process the digital received signal according to the second control parameter.

16. The method according to claim 14, characterized in that In the case where there are multiple transmitting channel devices and they are turned on at the same time, the processing of the radar signal to be transmitted according to the first control parameter by the multiple transmitting channel devices includes: According to the first control parameter, the first pseudo code generating unit is instructed to output a chip sequence and to superimpose a corresponding Walsh code on the output chip sequence.

17. The method according to claim 16, characterized in that The step of processing the received echo signal according to the second control parameter by one or more receiving channel devices comprises: According to the second control parameter, the accumulator is instructed to multiply the sign of the Walsh code with the signal input to the accumulator before accumulation, so as to distinguish different transmission channels.

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