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 includes: one or more transmitting channel devices for processing a radar signal to be transmitted according to a first control parameter to generate a transmitted signal; one or more receiving channel devices for receiving an echo signal of the transmitted signal and processing the received echo signal according to a second control parameter to obtain a received signal; and a control processor for performing 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 set by the control processor. The present application relates to a radar system capable of defining parameters, which can be compatible with various systems, such as FMCW radar, PMCW radar, pulse radar and other systems, and can achieve the effect of flexibly selecting a suitable technical system as needed.

Description

Technical Field

[0001] This 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 radars are being increasingly installed in vehicles. Most of the current vehicle-mounted radar products on the market are continuous wave radars. Among them, the most mainstream technical solution is the frequency modulated continuous wave (FMCW) radar. In recent years, the phase modulated continuous wave (PMCW) radar has also become an important development trend for vehicle-mounted radars due to its unique advantages (such as high accuracy and strong anti-interference ability).

[0003] The FMCW radar directly generates a frequency modulated signal through a voltage controlled oscillator (VCO) of a phase locked loop. This signal is subsequently multiplied in frequency and then fed to the transmitting channel for transmission, and is mixed with the echo signal at the receiving end. For the PMCW radar, its local oscillator generates a single frequency signal which is multiplied in frequency and used as the carrier frequency. This carrier frequency is modulated by the phase encoding signal generated by the phase modulator on the transmitting channel and then transmitted, and is also mixed with the echo signal at the receiving end.

[0004] Since the FMCW radar emits a frequency modulated signal (the frequency of the signal changes with time), to ensure the accuracy of radar measurement, strict requirements are imposed on the frequency locking speed, frequency modulation linearity, power flatness, etc. However, the local oscillator of the PMCW radar is a single frequency signal and does not require frequency modulation, so its requirements for RF link devices including the frequency source are lower.

[0005] In the echo signal link, under the FMCW radar system, after the echo signal passes through mixing demodulation and low-pass filtering, the echo signals of different distance targets are reflected as different frequency points on the signal spectrum after mixing and filtering. The relationship between the magnitude of its 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]

[0007] Where R is the distance of the target relative to the radar, c is the speed of light, k is the sweep slope, and F is the frequency value corresponding to the target at this distance R. For example, when R = 200m and k = 30MHz / us, it can be obtained that F = 4MHz. Generally speaking, the frequency value F is basically in the order of MHz and below, so the FMCW radar can use an ADC (analog-to-digital converter) with a sampling rate of dozens of MHz.

[0008] 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 sampling rate of the ADC needs to cover the phase modulation rate, that is, the signal bandwidth. Therefore, the sampling rate of the ADC generally requires at least the GHz level. So, compared with FMCW radar, PMCW radar poses higher requirements for the sampling rate of the ADC. At the same time, the increase in the sampling rate will inevitably lead to an increase in power consumption. To balance this, the bit width of the ADC in PMCW radar will be designed to be lower. The bit width of the ADC in FMCW radar chips is generally about 12 bits, while that in PMCW radar chips may be only about 6 bits.

[0009] After the ADC acquires the original data, in the PMCW system, the method of matched filtering is used to extract the range dimension information of the received echo, while in the FMCW system, it is processed based on the Fourier transform FFT. Combining with specific coding methods, it is easier for the radar under the matched filter to achieve simultaneous transmission of multiple antennas or multiple devices. Specifically, in the PMCW system, orthogonal spreading codes can be assigned to different antennas or different devices to avoid mutual interference between antennas or devices. These are the advantages of PMCW radar in signal processing. However, at the same time, the influence of Doppler phase shift on the radar measurement accuracy is more obvious in the PMCW system, and it is necessary to optimize the phase coding design or add a Doppler compensation algorithm at the signal processing end.

[0010] In addition, the most core advantage of PMCW radar compared with FMCW radar is its stronger anti-interference ability. The RF signal of FMCW radar needs to occupy a large bandwidth (the larger the bandwidth used, the higher the range resolution), while the available frequency band for vehicle-mounted radar is limited: 76 - 81 GHz. Therefore, as the number of radars increases, the interference between radars will undoubtedly continue to deteriorate.

[0011] As two main technical routes in continuous wave radar, FMCW and PMCW radars each have their own advantages and disadvantages, and there are often difficult problems that are difficult to balance in actual design.

[0012] In addition to continuous-wave radar, pulsed radar is also an important technical format in radar technology. Compared with continuous-wave radar, pulsed radar only receives signals and does not transmit any signals for most of the time, and only transmits pulsed signals with a very short duration in a small part of the time. Therefore, at the same peak transmit power, the total transmit energy of pulsed radar is much smaller than that of continuous-wave radar. However, pulsed radar is more often used in long-range radar detection scenarios (such as military scenarios), and its peak transmit power is increased by several orders of magnitude compared with civilian scenarios. In such a scenario, if the continuous-wave radar format is still used, the transmit signal will leak extremely high transmit power to the receiver, which may cause damage to the receiving circuit, and at the same time, there are extremely high requirements for the dynamic range of the received echo power. In contrast, pulsed radar controls transmission and reception through a transmit-receive switch component in a time-division manner, avoiding receiving signals while transmitting signals, thus avoiding the problem of direct leakage of transmit power to the receiver.

[0013] In summary, both continuous-wave radar and pulsed radar are important technical formats in current radar technology. Among them, continuous-wave radar includes (but is not limited to) two sub-formats: FMCW and PMCW. Different formats are suitable for different application scenarios and requirements, corresponding to different implementation schemes. Summary of the Invention

[0014] In the prior art, for different radar formats, there are different implementation schemes in terms of hardware. When a device (such as a vehicle) supports one format, it often cannot support other formats. And different formats have their own advantages and disadvantages, and are suitable for different application scenarios and requirements. The present application relates to a radar system capable of defining parameters, which can be compatible with various formats, such as being compatible with formats such as FMCW radar, PMCW radar, and pulsed radar, and can achieve the effect of being able to flexibly select a suitable technical system as needed.

[0015] According to one aspect of the present application, there is provided a radar system, characterized in that it includes:

[0016] One or more transmit channel devices, configured to process the radar signal to be transmitted according to a first control parameter to generate a transmit signal;

[0017] One or more receive channel devices, configured to receive the echo signal of the transmit signal and process the received echo signal according to a second control parameter to obtain a receive signal; and

[0018] A control processor, configured to perform read and write control on the first control parameter and the second control parameter connected to the system bus, wherein the first control parameter and the second control parameter are preset in the storage medium of the radar system and / or set by the control processor.

[0019] According to another aspect of the present application, there is provided a radar signal processing method, characterized by comprising:

[0020] Processing the radar signal to be transmitted according to a first control parameter through one or more transmitting channel devices to generate a transmitted signal; and

[0021] Receiving the echo signal of the transmitted 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;

[0022] Wherein, the first control parameter and the second control parameter are preset in the storage medium of the radar system and / or set by a control processor.

[0023] According to the radar system and the radar signal processing method provided by the present application, in view of the respective characteristics of different radar systems, the implemented radar system can support different radar systems simultaneously. For example, it can support three different radar systems, namely FMCW, PMCW, and pulsed radar, at the same time. Moreover, it can define the control parameters, pulse waveforms, and receiving algorithms of the radar system. The radar system can process signals of different radar systems, making the radar system highly versatile. Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without exceeding the scope of protection required by the present application.

[0025] Figure 1 It is a block diagram of the composition of the radar system.

[0026] Figure 2 It is of Figure 1 The structural diagram of the transmitting channel device in the radar system shown according to an embodiment of the present application.

[0027] Figure 3 It is of Figure 1 The structural diagram of the receiving channel device in the radar system shown according to an embodiment of the present application.

[0028] Figure 4 It is of Figure 1 The structural diagram of the receiving channel device in the radar system shown according to another embodiment of the present application.

[0029] Figure 5 It is of Figure 4 The structural diagram of the dispersion compensation unit in the receiving channel device shown according to an embodiment of the present application.

[0030] 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.

[0031] Figure 7 It is according to an embodiment of the present application Figure 4 The structural diagram of the correlator in the receiving channel device shown.

[0032] Figure 8 It is a code correlation schematic diagram under the PMCW system according to an embodiment of the present application.

[0033] Figure 9 It is a schematic diagram of the transmitted signal under the FMCW system according to an embodiment of the present application.

[0034] Figure 10 It is a working flow chart of a radar system under the PMCW and pulse radar systems according to an embodiment of the present application.

[0035] Figure 11 It is a working flow chart of a radar system under the FMCW system according to an embodiment of the present application.

[0036] Figure 12 It is a flow chart of a radar signal processing method according to an embodiment of the present application. Detailed implementation manners

[0037] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts fall within the protection scope of the present application.

[0038] Figure 1 It is a block diagram of the composition of a radar system. As Figure 1 shown, the system includes a transmitting channel device, a receiving channel device, and a control processor. Among them, the number of the transmitting channel device and the receiving channel device can be one or more. As Figure 1 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 communicate with each other through a bus. According to a specific embodiment, the control processor can be a CPU.

[0039] As Figure 1 shown, the system further includes an XTAL (External Crystal Oscillator) module that generates a clock source, and the clock output by the XTAL module is set as clkXTAL . One of the output clocks of the XTAL is given to the RFPLL phase-locked loop module, and the RFPLL multiplies its frequency to the radio frequency local oscillator signal LO. For millimeter-wave radar applications, the clock frequency is usually between 76 and 81 GHz. The other output clock of the XTAL is given to the BBPLL phase-locked loop module, and this module multiplies the clk XTAL frequency, and outputs four clocks, which are respectively the sampling clock clk DAC of the DAC (Digital-to-Analog Converter), the sampling clock clk ADC of the ADC, the baseband digital signal processing clock clk BB , and the control processor clock clk CPU .

[0040] According to an embodiment, taking the application of a millimeter-wave radar as an example, the radio frequency local oscillator frequency is around 79 GHz and the signal bandwidth is 1 GHz. The frequencies of these several clocks can be set according to the following parameters respectively:

[0041] F XTAL = 38.4 MHz

[0042] F LO = 79.104 GHz

[0043] F DAC = 5990.4 MHz

[0044] F ADC = 1996.8 MHz

[0045] F BB = 998.4 MHz

[0046] F CPU = 499.2 MHz

[0047] Among them, under the given XTAL clock, the multiplication factors of the multiple clocks output by the RFPLL and BBPLL relative to the XTAL clock can be adjusted according to the carrier frequency and bandwidth of the radar signal as needed, and can be flexibly configured in a software-defined manner.

[0048] According to an embodiment, Figure 1 the radar system shown also includes a radar data coprocessor. In Figure 1In the radar system shown, there are M transmit channels and N receive channels in total, so that M×N virtual array elements can be formed, and an array antenna is formed to realize capabilities such as angle measurement and radar imaging. The control parameters of all transmit channel devices are connected to the system bus through the register interface and can be read and written through the control processor connected to the bus. The control parameters of all receive channel devices are also connected to the system bus through the register interface. At the same time, the processed data in the receive channels is also connected to the system bus for the radar data coprocessor to directly read through DMA (Direct Memory Access).

[0049] As Figure 1 shown, the control processor is mounted on the bus and is responsible for the execution logic of the entire system. The read and write control of each transmit channel device and receive channel device by the control processor is carried out on the scale of a radar signal (for example, 1us) so that most operations on the radar signal can be defined by the control processor, for example, can be defined by the software inside the control processor.

[0050] In Figure 1 the embodiment shown, the radar data coprocessor is responsible for implementing subsequent radar signal processing related algorithms on the raw data processed by the receive channel device, including operations such as FFT in the slow time domain, FFT in the angle domain, and matrix decomposition. 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 receive 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 receive channel device is the channel impulse response and signal after correlation operations on the sampled data. In the three formats, the data transmission format of the signal is exactly the same and all represent the echo information in the range (or fast time) dimension.

[0051] Figure 2 is a structure diagram of a transmit channel device in a radar system according to an embodiment of the present application Figure 1 shown. As Figure 2 shown, the transmit channel device includes a digital baseband transmit channel, a first DAC, and an analog transmit channel. Among them, the digital baseband transmit channel includes a first pseudo-code generation unit, a first upsampling filter unit, and a first digital upconversion unit connected in sequence. The digital baseband transmit channel is used for digital baseband processing of the radar signal to be transmitted to generate a digital signal; the first DAC is connected to the digital baseband transmit channel and is used to convert the digital signal from the digital baseband transmit channel into an analog signal; the analog transmit 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 transmit channel is used for analog processing of the analog signal to generate a transmit signal.

[0052] In one embodiment, the structure of the digital up-conversion unit is as shown in Figure 6 . In Figure 6 , the input IQ complex signal is multiplied by a complex carrier signal (composed of the cosine real part and the sine 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 change in phase each time, is the sweep rate, which determines the amount of change in frequency each time. These three parameters can also be configured by a control processor as part of the control parameters. The sweep frequency F linearly increases at the speed of , and at the same time, the sweep phase changes according to the rule of increasing by F each time. The corresponding cosine and sine values are calculated based on the real-time phase of the complex carrier signal, and complex multiplication with the input signal completes the digital frequency conversion.

[0053] The output data of the digital up-conversion unit is I / Q two-channel data with a sampling rate of F DAC . The I / Q two-channel data is directly sent to two DACs for digital-to-analog conversion. The analog signals after DAC conversion are then sent to the I / Q two-channel analog processing units. After passing through the first baseband filter, the first radio frequency mixer, and the power amplifier, they are sent to the antenna unit for transmission into space.

[0054] For the transmitting channel device, corresponding control parameters can be determined so that the transmitting channel device can process the radar signal to be transmitted according to the corresponding control parameters to generate a transmitted signal. According to one embodiment, the control parameters corresponding to the transmitting 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 transmitting channel device can include the sweep bandwidth B, the frequency increment value , the length P of a radar signal, the transmission power, etc. Moreover, for different radar systems, the control parameters can instruct the units or devices in the transmitting channel device to perform different processes.

[0055] According to a specific embodiment, in the FMCW system, since the transmitted waveform does not involve a pseudo-code, the control parameters can instruct the first pseudo-code generation unit to output all-1 chip symbols, 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 symbols are input to the first up-sampling and filtering unit, and the control parameters instruct the first up-sampling and filtering unit to use an all-1 rectangular window for filtering, and the sampling rate is increased to F DAC, the filtered baseband signal can still be a signal of all 1s 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 frequency sweep processing of [-B / 2, B / 2] on the radar signal to be transmitted. After passing through the DAC, it becomes an analog continuous signal and is output to the transmitting radio frequency module. The baseband analog output signal of a single radar signal can be expressed as:

[0056]

[0057] where is the non-zero duration of a single radar signal. Within the time, the frequency of the baseband transmission signal output by the DAC linearly increases from -B / 2 to B / 2 over time, completing a linear frequency sweep with a bandwidth of B. represents the radar signal period. For there is , and the duty cycle of the generated FMCW signal is , as shown in Figure 9 . In particular, if , then the signal duty cycle is 1.

[0058] According to the digital up-conversion or digital down-conversion unit shown in Figure 6 , the control processor configures the frequency sweep rate , the initial sweep frequency F, and the initial phase . The sweep frequency F linearly increases at a speed of , and at the same time, the sweep phase changes according to the rule of increasing by F each time. For example, in the waveform given above, the parameters configured by the control processor for the digital up-conversion unit are = k, F = -B / 2, = 0.

[0059] According to another specific embodiment, in the PMCW or pulsed radar system, the pseudo-code generation unit generates a chip sequence with excellent autocorrelation characteristics. For simplicity, the chip sequence can be composed of ±1, that is, a sequence with 0° / 180° phase modulation. Similar to FMCW, the generated PMCW chip sequence can also have a certain duty cycle, that is, it is ±1 chip symbols for a part of the time, and the chip symbols for the rest of the time are 0. The control parameter can instruct the first pseudo-code generation unit to generate a chip sequence with low sidelobe autocorrelation characteristics. The first up-sampling and filtering unit performs a convolution operation on the chip sequence to form a baseband digital waveform. Since the PMCW or pulsed radar wave signal does not require baseband frequency conversion, the first digital up-conversion unit maintains a fixed frequency and does not perform frequency sweep, and does not process the radar signal to be transmitted (PMCW or pulsed radar wave signal). Then, it becomes an analog signal through the DAC and is output to the radio frequency module. The output signal corresponding to a single radar signal can be expressed as:

[0060] ,

[0061] where \(K\) represents the number of chips in the chip sequence, is the duration of a single chip, \(\in\{\pm1\}\) 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.

[0062] In one embodiment, in order to reduce the complexity of hardware implementation, the pseudo-code generation units of all the transmitting channel devices can share a pseudo-code generation unit, that is, all the transmitting channels use the same pseudo-code. In the case where multiple transmitting channel devices are turned on simultaneously, the pseudo-code generation units of each transmitting channel superimpose a Walsh code of their respective channels on top of the shared pseudo-code. In addition, the NCO (Numerically Controlled Oscillator) in the digital up-conversion unit can also be shared among the respective transmitting channels.

[0063] For different radar systems, multiple transmitting channel devices can sequentially turn on signal transmission in a time-division manner, or can turn on simultaneously for signal transmission. In the case where multiple transmitting channel devices are turned on simultaneously, it is usually necessary to superimpose the respective Walsh codes on the transmitting channels to ensure the signal orthogonality between the transmitting channels.

[0064] In the case where multiple transmitting channel devices are turned on simultaneously, the control parameter can instruct the first pseudo-code generation unit of each transmitting channel to superimpose a Walsh code of its respective transmitting channel on top of the generated pseudo-code. According to one embodiment, the length of the Walsh code is different for different supported numbers of transmitting channels. For the number of transmitting channels \(M\), the length of its Walsh code is .

[0065] In one embodiment, it is allowed that the generated PMCW radar signal is repeated \(L\) times so that the receiving channel can accumulate the received radar signal to improve the signal-to-noise ratio. For the case where multiple transmitting channel devices are turned on simultaneously for signal transmission, after adding the Walsh code, the generated transmitted radar signal is as Figure 8 shown, where the secondary code in the figure 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, zeros are padded. The total number of chips is denoted as P, and the number of padded chips is P - KL. The transmitted signal after repetition and zero-padding is multiplied by +1 or -1 as a whole according to the polarity of the Walsh code, thus completing the generation of the transmitted signal under a single Walsh symbol. The transmission channel can generate the transmitted signal under subsequent Walsh symbols in the same way according to the length of the Walsh code. In particular, L can take the value of 1, indicating that there is only one radar signal under a single Walsh symbol.

[0066] In the pulsed 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 for a single radar signal can also be expressed as:

[0067] 。

[0068] The main difference between the pulsed radar and the PMCW radar is that for the pulsed radar, usually the value of K is small and L = 1, and the duration K of the non-zero chips is much smaller than the radar signal period, making the transmitted signal be 0 most of the time and the duty cycle very small. In this way, the radar transmission channel and the reception channel can alternate through time division to avoid the direct leakage of the transmitted signal to the input of the receiver. In contrast, for the PMCW radar, the duration of the non-zero chips is comparable to or even equal to the radar signal period, and the duty cycle of the transmitted signal is relatively large.

[0069] For the case of multiple transmit antennas, in order to avoid interference between different transmit antennas, different transmit channel devices can transmit signals in a time-division manner, or as described above, modulate the signals transmitted by different transmit channel devices with Walsh codes so that the transmitted signals of different antennas can be transmitted simultaneously. Here, a Walsh code division transmission example for 2 transmit channel devices (corresponding to 2 transmit antennas) is given. For simplicity of expression, it is assumed here that L = 1 and there is no zero-padding operation. Considering the case of 2 antennas, for the signals of 2 consecutive radar signal periods transmitted simultaneously, the first antenna transmits x(t) in both radar signal periods; the second antenna transmits x(t) in the first radar signal period and -x(t) in the second radar signal period, thus 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 transmit antennas: for the case of M transmit antennas, Walsh codes of length are required to ensure the orthogonality of the code sequences assigned to different transmit antennas. Therefore, all M transmit antennas need to transmit a total of a radar signal, so that the receiving channel device can distinguish the echo signals of different transmitting antennas. In addition, it is supplemented here that the transmitted radar signal x(t) can be the transmission symbol of FMCW, PMCW or pulsed radar.

[0070] According to an embodiment, when multiple transmitting channel devices sequentially turn on signal transmission in a time-division manner, the NCO in the first digital up-conversion unit can be shared among the respective transmitting channels.

[0071] Figure 3 is according to an embodiment of the present application Figure 1 The structural diagram of the receiving channel device in the radar system shown. As Figure 3 shown, the receiving channel device includes an analog receiving channel, an ADC, and a digital baseband receiving channel. Among them, the analog receiving channel includes a low-noise amplifier, a second RF mixer, and a second baseband filter connected in sequence. The analog receiving channel is used to perform analog processing on the received echo signal to generate an analog received signal; the ADC is connected to the analog receiving channel and is used to convert the analog received signal from the analog receiving channel into a digital received 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. The digital baseband receiving channel is used to perform digital baseband processing on the digital received signal to generate a received signal. In the receiving channel device, the received signal becomes a baseband digital signal after amplification, mixing, and ADC sampling. In the digital processing part, this digital signal first passes through an energy detection module to detect the saturation situation of the ADC output. If there are too many saturation sampling points, the receiving gain should be appropriately reduced; otherwise, the receiving gain can be appropriately increased.

[0072] To solve the influence of the direct part of the transmitted signal on the receiving channel in radar applications, an independent interference cancellation signal module can be set in the receiving channel device. Figure 4 is according to another embodiment of the present application Figure 1 The structural diagram of the receiving channel device in the radar system shown. Compared with Figure 3 In comparison, Figure 4 the receiving channel device shown in addition to including an analog receiving channel, an ADC, and a digital baseband receiving channel, also includes an interference cancellation signal module and a coupler TO. As Figure 4 shown, the interference cancellation signal module includes 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 RF mixer, and an attenuator ATT connected in sequence. The interference cancellation signal module is used to generate an interference cancellation signal; the coupler is connected to the interference cancellation signal module and the analog receiving channel and is used to perform inverse coupling of the interference cancellation signal and the received echo signal.

[0073] 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 upconversion. Among them, the processes of pseudo-code generation, upsampling filtering, and digital upconversion are the same as those of the signal transmission process. Therefore, as an alternative, the digital signal before 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) filter, so the delay of the transmitting channel can also be compensated.

[0074] The function of the interference cancellation signal module is equivalent to the signal synthesis of all transmitting 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. After the analog receiving channel amplifies, downconverts, and filters the signal, it is sent to the ADC, and the ADC converts the analog signal into a digital signal at the sampling rate F ADC and sends it to the digital baseband receiving channel. The digital baseband receiving channel performs energy detection on the signal and then sends it to the digital downconversion unit.

[0075] 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 can include the sweep bandwidth B, the frequency increment value , the length P of a radar signal, the receiving gain, etc. Moreover, for different radar systems, the control parameters can instruct the units or devices in the receiving channel device to perform different processes. According to a specific embodiment, in the FMCW system, the control parameters instruct the digital downconversion unit to perform a frequency sweep in the same frequency range [-B / 2, B / 2] as the transmitting channel device. 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 transmitted signal arrives at the receiving channel.

[0076] For the FMCW radar system, the input signal first performs a difference frequency process on the digital received signal in the digital downconversion NCO. The phase of the complex carrier signal generated by the NCO is opposite to the phase of the digital upconversion NCO in the transmitting channel, thus achieving the difference frequency effect. Since after the difference frequency, the echoes of scatterers at different distances are manifested as difference frequency signals with different frequencies, in order to extract the frequency of this difference frequency signal, an FFT operation should be performed on this signal subsequently. The FFT operation here is performed by the FFT unit in the correlator, such as Figure 7As shown. Finally, after the FFT operation is completed, the same FFT signal enters the multi-channel accumulator for coherent accumulation to obtain the echo signals of each transmitting channel for the current receiving channel. When the Walsh code is superimposed on the transmitting channel device, after the FFT operation is completed, the same FFT signal enters the multi-channel accumulator for coherent accumulation according to the Walsh code polarities of different transmitting channels to obtain the echo signals of each transmitting channel for the current receiving channel. Among them, the number of accumulators is equal to the number of channels.

[0077] According to a specific embodiment, in the PMCW or pulsed radar system, the control parameter instructs the digital down-conversion unit to directly use a fixed frequency same as that at the transmitting end for frequency conversion operation.

[0078] For the PMCW or pulsed radar system, the digital down-conversion NCO does not need to work and does not perform phase rotation on the baseband received signal. Subsequently, the signal enters the correlator to complete the correlation operation with the local code, where the local code is the pseudo-code sequence adopted by a single radar signal. The specific implementation of the correlator is as Figure 7 shown. Its basic principle is to utilize the equivalence between the cyclic convolution operation in the time domain and the multiplication operation in the frequency domain, and perform the multiplication operation in the frequency domain and then transform the frequency domain signal back to the time domain. Therefore, first, the input signal is transformed to the frequency domain by the FFT module, and a product operation is performed in the frequency domain with the FFT result of the time-reversed local code. The purpose of time-reversing the local code is to convert the cyclic convolution into a cyclic correlation operation. Finally, the frequency domain product result is transformed back to the time domain via the IFFT and input to the subsequent accumulator to complete the accumulation. Among them, when the Walsh code is superimposed on the transmitting channel device, the accumulator completes the accumulation according to the Walsh code polarities of different channels.

[0079] The signal after digital down-conversion is sent to the correlator for correlation or FFT operation, as Figure 7 shown. In the PMCW or pulsed radar system, for the correlator of each receiving channel, it is necessary to process M transmitting signals. When the same pseudo-code sequence is adopted for these M transmitting signals, a single correlation module can be used in the correlator, and this correlator adopts the FFT fast algorithm:

[0080]

[0081] Among them, represents the conjugate of the FFT result of the time-reversed code sequence, and this result can be pre-generated by the control processor and stored in the correlator, without real-time calculation; Indicates that 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 mode, the operation result is directly sent to the radar data co-processor through DMA for subsequent operations; if it is the PMCW or pulsed radar mode, the result is multiplied point-by-point with the stored locally, and then an IFFT is performed again to obtain the correlation result of a radar signal.

[0082] The FFT result or correlation result obtained from the above operations is then sent to the subsequent M-channel accumulators for accumulation on the secondary code. In the case where Walsh codes are superimposed on the transmit channel, when each accumulator accumulates each symbol, the Walsh code of the symbol can be configured through control parameters (such as through the control processor). The accumulator multiplies the symbol of the Walsh code with the input signal before accumulation to distinguish different transmit channels. The result of the accumulator can be sent to the radar data co-processor through DMA for subsequent processing.

[0083] In the case where Walsh codes are superimposed on the transmit channel, the dispersion compensation unit in the interference cancellation signal module includes a Walsh flip sub-unit and an FIR filter, as Figure 5 shown. Among them, the Walsh flip sub-unit corresponds to the transmit 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 indication of the control parameter corresponding to the receive channel device to generate a Walsh flip signal. The FIR filter is connected to the Walsh flip sub-unit and is used to process the Walsh flip signal to generate a delay compensation signal.

[0084] Each receiving channel needs to eliminate the superimposed signals of multiple transmitting channels. Therefore, the dispersion compensation unit needs to perform a flipping operation on a piece of pseudo-code data with the same Walsh code as each transmitting channel, and then pass it through an FIR filter respectively to restore the dispersion and delay effects of each transmitting channel. Finally, the signals are summed before being sent to the DAC. The coefficients used by the FIR are calculated and configured by the processor. Since the dispersion effects and delays of the self-interference signals of different transmitting paths are different, the FIR coefficients should be obtained by superimposing the dispersion delay coefficients of the self-interference of each transmitting path multiplied by the Walsh code polarities of each channel. In actual implementation, the dispersion delay coefficients of the self-interference of each transmitting path can be iteratively calculated by the control processor using the LMS (Least Mean Squares) algorithm according to the magnitude of the self-interference signal in the echo of each transmitting path. The baseband digital signal after dispersion compensation is converted into an analog signal by the DAC, and then, after quadrature up-conversion and an attenuator, it is used as the RF self-interference signal. This signal is coupled in antiphase with the echo signal to achieve the purpose of self-interference cancellation. Among them, 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 transmitting channel can be achieved by adjusting the amplitude of the FIR coefficients.

[0085] Figure 10 is a flowchart of the operation of a radar system in the PMCW and pulse radar modes according to an embodiment of the present application. In Figure 10 the embodiment shown, the transmissions of multiple transmitting channels are made orthogonal by Walsh codes. Before starting the transmission and reception, 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 codes of each transmitting channel, and the gains of the transmitting and receiving channels, etc. After the parameter configuration is completed, the transmission and reception processing can be started. M transmitting channels are turned on simultaneously, and the radar signal transmission under the modulation of Walsh code elements is completed in the manner described above, and the corresponding waveform is as shown in Figure 8 where the secondary code in the figure is the Walsh code. N receiving channels are turned on simultaneously with the transmitting channels. First, the dispersion compensation FIR filter coefficients for self-interference cancellation are estimated. The implementation method is to feedback-control the parameters of the dispersion compensation filter according to the magnitude of the self-interference signal in the accumulator result until the self-interference signal is eliminated to the lowest level. After this step is completed, the N receiving channels can perform the actual reception of the signal frames and output the echo results that can be used for target detection or area imaging. Among them, for the pulse radar mode, the self-interference cancellation function may not be turned on, and the self-interference can be avoided by time-division opening of the transmission and reception.

[0086] Figure 11 is a flowchart of the operation of a radar system in the FMCW mode according to an embodiment of the present application. In Figure 11In the illustrated embodiment, the transmissions of multiple transmitting channels are made orthogonal by time division. Before starting the transceiver operations, the transceiver parameters should be configured first, including parameters such as the sweep range B, the frequency change rate Δf, the radar signal length P, and the gains of the transceiver channels. Each transmitting channel is turned on in turn by time division, and when each transmitting channel is turned on, the N receiving channels are all turned on simultaneously. First, the dispersion compensation FIR filter coefficients for self-interference cancellation are estimated. The implementation method is to feedback-control the dispersion compensation FIR filter coefficients according to the magnitude of the self-interference signal in the FFT result until the self-interference signal is eliminated to the lowest level. After completing this step, the N receiving channels can perform the actual reception of the signal frames and output the echo results that can be used for target detection or area imaging.

[0087] It should be noted that the PMCW or pulsed radar systems can also turn on multiple transmitting channels by time division. The startup methods of their respective transceiver channels are the same as those of the FMCW radar transceiver process described above, and will not be elaborated here. Similarly, the FMCW radar system can also turn on multiple transmitting channels simultaneously by adding Walsh codes. The corresponding startup methods of the transceiver channels are the same as those of the PMCW or pulsed radar transceiver processes described above.

[0088] Based on the above embodiment, according to one aspect of the present application, a radar signal processing method is provided. Figure 12 It is a flowchart of a radar signal processing method according to an embodiment of the present application. As Figure 12 shown, the method includes the following steps:

[0089] Step S1201, processing the radar signal to be transmitted by one or more transmitting channel devices according to a first control parameter to generate a transmitted signal; and

[0090] Step S1202, receiving the echo signal of the transmitted signal by one or more receiving channel devices and processing the received echo signal according to a second control parameter to obtain a received signal;

[0091] wherein, the first control parameter and the second control parameter are preset in the storage medium of the radar system and / or set by a control processor.

[0092] In some alternative embodiments, step S1201 may include:

[0093] In the FMCW radar system, according to the first control parameter, instruct the first pseudo-code generation unit to output a full-1 chip sequence, the first upsampling filter unit uses a full-1 rectangular window filter, and the first digital upconversion unit performs a sweep processing of a preset sweep bandwidth on the radar signal to be transmitted; and

[0094] In the PMCW or pulsed radar mode, according to the first control parameter, the first pseudo-code generation unit is instructed to generate a chip sequence with low sidelobe autocorrelation characteristics. The first upsampling and filtering unit performs the convolution operation on the chip sequence, and the first digital upconversion unit does not process the radar signal to be transmitted.

[0095] In some alternative embodiments, when multiple transmitting channel devices are turned on simultaneously, step S1201 may include:

[0096] According to the first control parameter, the first pseudo-code generation unit is instructed to output a chip sequence and superimpose the corresponding Walsh code on the output chip sequence.

[0097] In some alternative embodiments, step S1202 may include:

[0098] In the FMCW radar mode, according to the second control parameter, the digital downconversion unit is instructed to perform difference frequency processing on the digital received signal; and

[0099] In the PMCW or pulsed radar mode, according to the second control parameter, the digital downconversion unit is instructed not to process the digital received signal.

[0100] In some alternative embodiments, step S1202 may include:

[0101] According to the second control parameter, the accumulator is instructed to multiply the symbol of the Walsh code and the signal input to the accumulator before accumulation to distinguish different transmitting channels.

[0102] According to the radar system and the radar signal processing method provided by the present application, in view of the respective characteristics of different mode radars, the implemented radar system can support different radar modes simultaneously. For example, it can support three different radar modes: FMCW, PMCW, and pulsed radar. Moreover, it can define the control parameters, pulse waveforms, and receiving algorithms of the radar system. The radar system can process signals of different radar modes, allowing for flexible switching according to the actual application scenario, making the radar system highly versatile. In addition, the present application supports multi-transmit and multi-receive channel processing and ensures the orthogonality between the transmitting channels. Therefore, it supports the use of a large-scale antenna array for high-resolution imaging. Additionally, the present application supports self-interference cancellation, which can significantly improve the dynamic range of the received signal at the receiver input.

[0103] The above has introduced the embodiments of the present application in detail. Specific examples are used in this article to elaborate on the principle and implementation manner 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, any changes or deformations made by those skilled in the art based on the idea of the present application, within the specific implementation manner and application scope of the present application, fall within the scope of protection of the present application. In summary, the content of this specification should not be construed as a limitation to 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, configured 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; Wherein, 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 connected to the first DAC, comprising a first baseband filter, a first radio frequency mixer, a power amplifier and an antenna unit connected in sequence, the analog transmission channel being used to perform analog processing on the analog signal to generate the transmission signal; Wherein, 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, connected to the ADC, comprising an energy detection unit, a digital down-conversion unit, a correlator and an accumulator connected in sequence, the digital baseband receiving channel being used to perform digital baseband processing on the digital received signal to generate the received signal; 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.

2. The radar system according to claim 1, 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.

3. The radar system according to claim 2, 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.

4. The radar system according to any one of claims 1 to 3, 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.

5. The radar system according to claim 1, 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.

6. The radar system according to claim 5, 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.

7. The radar system according to claim 6, 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.

8. 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; Wherein, the first control parameter and the second control parameter are preset in a storage medium of the radar system and / or set by a control processor; Wherein, 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 connected to the first DAC, comprising a first baseband filter, a first radio frequency mixer, a power amplifier and an antenna unit connected in sequence, the analog transmission channel being used to perform analog processing on the analog signal to generate the transmission signal; Wherein, 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, connected to the ADC, comprising an energy detection unit, a digital down-conversion unit, a correlator and an accumulator connected in sequence, the digital baseband receiving channel being used to perform digital baseband processing on the digital received signal to generate the received signal; 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.

9. The method according to claim 8, 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.

10. The method according to claim 8, 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.

11. The method according to claim 10, 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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