A 4D millimeter-wave radar design method based on phase modulation

Abstract

The present invention discloses a 4D millimeter wave radar design method based on phase modulation, which specifically relates to the field of 4D detection technology, including step 1: designing the fast time dimension pulse modulation mode of the millimeter wave radar as a frequency modulated continuous wave, and transmitting M×N repeated pulses in the slow time dimension within a coherent processing cycle; step 2: the N pulses used for transmitting orthogonal modulation can be phase-encoded for Q transmission channels, and Q<2 N The present invention obtains orthogonal transmission signals through phase modulation in the slow time dimension; separates the signals of each transmission channel through signal demodulation at the receiving end; and synthesizes a two-dimensional array antenna by forming a virtual array in two dimensions of the antenna plane; the final two-dimensional array antenna can perform joint angle measurement in azimuth and elevation dimensions, and realize 4D detection without increasing the radar transceiver bandwidth; it can be widely used in millimeter-wave radar systems in the field of advanced driver assistance and autonomous driving.

Description

Technical Field

[0001] The present invention relates to the field of 4D detection technology, and more specifically, to a 4D millimeter wave radar design method based on phase modulation. Background Art

[0002] Under the premise of limited cost and size, millimeter-wave radar uses multiple input multiple output (MIMO) technology to form a virtual aperture in order to effectively perform joint detection in azimuth and elevation dimensions. The generation of a virtual aperture requires that the transmitted signal has orthogonality so that the radiation signal of each transmitting array element can be distinguished at the receiving end. Previous millimeter-wave radars often used a time-division orthogonal method, that is, different transmitting antennas radiate at different times, and the different transmitted signals are distinguished by time difference. Although this type of method can effectively achieve the orthogonality of the transmitted signal, due to the time-sharing transmission of different transmitting antennas, the synthesized radiation power is limited, and for moving targets, the phase change of the moving target caused by the time difference needs to be compensated at the receiving end, which is prone to compensation errors caused by Doppler ambiguity.

[0003] With the gradual promotion of millimeter-wave radar in assisted driving and unmanned vehicles, in order to avoid radar false alarms caused by elevated obstacles (such as pedestrian bridges and gantries) and low obstacles (such as manhole covers and cans), radar is urgently needed to have the ability to detect in the pitch dimension to achieve 4D detection. Summary of the invention

[0004] In order to overcome the above-mentioned defects of the prior art, an embodiment of the present invention provides a 4D millimeter-wave radar design method based on phase modulation. The technical problem to be solved by the present invention is: how to enable the radar to have the detection capability of the pitch dimension to achieve 4D detection.

[0005] To achieve the above object, the present invention provides the following technical solution: a 4D millimeter wave radar design method based on phase modulation, the specific operation steps are as follows:

[0006] Step 1: Design the fast time dimension pulse modulation mode of the millimeter wave radar as frequency modulated continuous wave (LFMCW), and transmit M×N repetitive pulses in the slow time dimension within a coherent process interval (CPI);

[0007] Wherein, N is the number of pulses used to transmit orthogonal phase modulation, M is the number of pulses used for Doppler velocity measurement, and the pulse duration is T;

[0008] Step 2: The N pulses used for transmitting orthogonal modulation can be used to phase encode the Q transmission channels, and Q < 2 N ;

[0009] The relative motion of the target will cause the Doppler frequency shift f d The phase mismatch caused This phase mismatch will cause a quadrature loss L;

[0010] because The maximum value of Therefore, reasonable selection of N and M can effectively inhibit L;

[0011] Step 3: After receiving the complete transmission signal, the orthogonal coded signals of different transmission channels are demodulated to separate the echo signals of different transmission channels;

[0012] The virtual receiving channels generated by the pairing of each transceiver channel are synthesized into a two-dimensional virtual receiving array in the horizontal X direction and the vertical Y direction;

[0013] For a certain space point, its projection angle in the X and Y directions is θ x and θ y , then beam synthesis based on digital phase shifting is performed according to the projection angle;

[0014] The phase shift angle corresponding to a certain element in the virtual array

[0015] Among them, d x is the relative distance of the array element in the X direction, d y is the relative distance of the array element in the Y direction; combined with the installation posture of the antenna array, it can be calculated by θ x and θ y Calculate the azimuth and elevation angle to achieve 4D detection of the radar.

[0016] In a preferred embodiment, the phase encoding in step 2 adopts but is not limited to Hadamard encoding, and the recursive formula of the N-order Hadamard orthogonal code is:

[0017] Technical effects and advantages of the present invention:

[0018] 1. The present invention obtains orthogonal transmission signals through phase modulation in the slow time dimension; separates the signals of each transmission channel through signal demodulation at the receiving end; synthesizes a two-dimensional array antenna by forming a virtual array in two dimensions of the antenna plane; the final two-dimensional array antenna can perform joint angle measurement in azimuth and elevation dimensions, and realize 4D detection without increasing the radar transceiver bandwidth; and can be widely used in millimeter-wave radar systems in the field of advanced driver assistance and autonomous driving;

[0019] 2. In this example of the present invention, phase modulation in the slow time dimension is used to realize the orthogonality of the transmission signals of each transmission channel. After orthogonal demodulation at the receiving end, each transmission channel signal is distinguished to form a virtual array in the azimuth and elevation dimensions, thereby realizing radar 4D detection; it effectively solves the problem of limited synthetic power of time-division MIMO radar and phase compensation error during Doppler ambiguity, and can effectively realize the formation of virtual aperture and realize radar 4D detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a block diagram of the radar system of the present invention.

[0021] Figure 2 Schematic diagram of radar timing relationship of the present invention.

[0022] Figure 3 The figure is a schematic diagram of the distribution of radar transceiver array elements of the present invention.

[0023] Figure 4 The figure is a schematic diagram of forming a radar virtual array of the present invention.

[0024] The reference numerals in the figure are: 100-display control part, 110-signal / data processing part, 120-millimeter wave transceiver integrated chip array, 130-transmitting antenna array, 140-receiving antenna array, 210-orthogonal coded modulation pulse signal period, 220-repeated pulse period within one CPI, 310-transmitting array element, 320-receiving array element, 400-virtual receiving array element formed by radar. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] The present invention provides a 4D millimeter wave radar design method based on phase modulation. In order to make the technical features and use methods of the present invention easy to understand, the present invention is further described in conjunction with the accompanying drawings. The specific operation steps are as follows:

[0027] Step (1) Design the block diagram of the 4D millimeter wave radar based on phase modulation as shown below: Figure 1 As shown, the radar is controlled by the display control part 100 for work command control and result display, and under its control, the signal / data processing part 110 performs Figure 2The millimeter wave transceiver integrated chip array 120 generates a transmission waveform under the drive of the timing control, and the generated waveform is radiated into space by the transmitting antenna array 130; the echo signal reflected by the object is received by the receiving antenna array 140 and fed into the millimeter wave transceiver integrated chip array 120, converted into a digital signal and then transmitted to the signal / data processing part 110 for signal / data processing, and finally the processing result is output to the display control part 100 for result display;

[0028] Step (2) is controlled by the signal / data processing section 110 Figure 2 The CPI pulse timing is generated; one CPI contains N×M pulse signals; N=16, and the 16 pulses are encoded based on Hadamard binary phase shift keying BPSK. In this example, 12 orthogonal codes are selected to modulate the transmission signal on 12 transmission channels; M=16, then the total number of pulses of one CPI is 256;

[0029] Step (3) construct the radar antenna array as follows: Figure 3 As shown, in this example, the antenna array includes 12 transmitting array elements 310 and 16 receiving array elements 320; the basic array element spacing dx in the horizontal direction of the antenna array is 0.5λ, and the basic array element spacing dy in the vertical direction is 1λ; in this example, the horizontal and vertical spacings of the transmitting array elements 310 and the receiving array elements 320 are as follows Figure 3 As shown in the logo;

[0030] Step (4) After the digital echo signal is input into the signal / data processing part, the orthogonal transmission signal is demodulated within one CPI, and the transmission signals of 12 transmission channels can be restored in 16 receiving channels; thus, the following can be generated: Figure 4 The virtual two-dimensional array shown includes a total of 16*12=192 virtual receiving array elements 400 formed by radars;

[0031] Step (5) Due to Figure 4 The synthetic virtual aperture array in is a sparse array, so the singular value thresholding SVT method can be used to fill the sparse array elements according to the echo signal; finally, the projection angle θ of the spatial pointing in the horizontal and vertical directions of the array is measured. x and θ y , and combined with the radar array attitude, the azimuth and pitch angle of the target relative to the radar carrier can be calculated, thereby realizing the radar's 4D detection.

[0032] Working principle of the present invention:

[0033] The present invention makes the transmission waveforms of each radar array element orthogonal by means of phase modulation; after receiving the complete transmission signal, the radar receiving channel demodulates the orthogonal coded signals of different transmission channels, thereby distinguishing the transmission signals of different transmission channels; combining the array element positions of the transmitting and receiving channels, a two-dimensional virtual array is formed to perform azimuth and elevation joint detection, thereby realizing the radar's 4D detection;

[0034] By generating phase-modulated orthogonal signals, without increasing the original transmit and receive bandwidth, the receiving unit can correctly distinguish the transmit signals of different array elements, thereby forming a virtual horizontal and vertical array, and realizing 4D detection of millimeter-wave radar in the dimensions of distance, azimuth, pitch, and speed.

[0035] Finally, a few points should be explained: First, in the description of this application, it should be noted that, unless otherwise specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, which may refer to mechanical connection or electrical connection, or internal communication between two components, or direct connection. "upper", "lower", "left", "right", etc. are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may change;

[0036] Secondly: In the drawings of the embodiments disclosed in the present invention, only the structures related to the embodiments disclosed in the present invention are involved, and other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of the present invention can be combined with each other;

[0037] Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A 4D millimeter wave radar design method based on phase modulation, characterized in that: The specific steps are as follows: Step 1: Design the fast-time pulse modulation mode of the millimeter-wave radar as a frequency-modulated continuous wave, and transmit in the slow-time dimension within one coherent processing cycle repetitive pulses; Wherein, N is the number of pulses used to transmit orthogonal phase modulation, M is the number of pulses used for Doppler velocity measurement, and the pulse duration is T; Step 2: The N pulses used for transmitting orthogonal modulation can be used to phase encode the Q transmission channels, which must satisfy ; The relative motion of the target will cause the Doppler shift The phase mismatch caused , this phase mismatch will cause orthogonality loss L; because The maximum value of ≪ , so the reasonable selection of N and M can effectively inhibit L; Step 3: After receiving the complete transmission signal, the orthogonal coded signals of different transmission channels are demodulated to separate the echo signals of different transmission channels; The virtual receiving channels generated by the pairing of each transceiver channel are synthesized into a two-dimensional virtual receiving array in the horizontal X direction and the vertical Y direction; For a certain space point, its projection angle in the X direction and Y direction is and , then beam synthesis based on digital phase shifting is performed according to the projection angle; The phase shift angle corresponding to a certain element in the virtual array ; in, is the relative distance of the array element in the X direction, is the relative distance of the array element in the Y direction, is the wavelength of the electromagnetic wave emitted; combined with the installation posture of the antenna array, it can be and Calculate the azimuth and elevation angle to achieve 4D detection of the radar.

2. The 4D millimeter wave radar design method based on phase modulation according to claim 1, characterized in that: The phase coding in step 2 adopts but is not limited to Hadamard coding, and the recursive formula of N-order Hadamard orthogonal code is: , .

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