Device for improving group delay of LO signal power divider of point cloud radar

Abstract

The invention provides a device for improving the group delay of a point cloud radar LO signal power divider, and the device comprises a main chip, a plurality of radio frequency chips, a power divider, a plurality of metal layers, a first strip-shaped transmission line, a second strip-shaped transmission line, a first signal hole, and a second signal hole. The output end of the main chip penetrates through the first signal hole and a first strip-shaped transmission line located in the PCB to be connected with the input end of the power divider, and the multiple output ends of the power divider penetrate through the multiple second signal holes and second strip-shaped transmission lines which are located in the PCB and are equal in length and phase to be connected with the input ends of the multiple radio frequency chips. Periodic backflow holes are formed in the two sides of the first strip-shaped transmission line and the two sides of the second strip-shaped transmission line, and line end points of the strip-shaped transmission lines are designed in a quasi-coaxial mode. According to the invention, the group delay difference value of the power division band-shaped transmission network can be reduced, the overall performance of the point cloud radar is improved, the stability and reliability of the system are improved, the structure is simple, the cost is low, the size is small, the processing and manufacturing are easy, and the method has important engineering application value.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle-mounted millimeter-wave radar, and in particular to a device for improving the group delay of a point cloud radar LO signal power divider. Background Art

[0002] The detection performance of 4D millimeter wave radar includes four aspects: distance, speed, azimuth, and pitch angle: 1) In distance detection, the main performance indicators include maximum detection distance, distance accuracy, and distance resolution. The main influencing factors are ADC sampling rate, frequency modulation slope, output power, sweep bandwidth, and signal-to-noise ratio. 2) In speed detection, the main performance indicators include maximum detection speed, speed accuracy, and speed resolution. The main influencing factors are Chirp period, effective frame period, and signal-to-noise ratio. 3) In azimuth detection, the main performance indicators include field of view, angle accuracy, and angle resolution. The main influencing factors are antenna spacing, azimuth, and the number of antennas. 4) In pitch angle detection, the main performance indicators include maximum pitch angle, pitch angle accuracy, and pitch angle resolution. The main influencing factors are antenna spacing, azimuth, and the number of antennas. Radar performance is limited by millimeter waves, analog circuit performance, processing power, and other factors.

[0003] For autonomous driving, sensors such as cameras, millimeter-wave radars, ultrasonic radars, and lidars are usually required, and the precise data collection time of these sensors is extremely important, while low group delay is the guarantee of system reliability. Due to the high resolution and high-density point cloud data requirements of 4D millimeter-wave imaging radars, 4D millimeter-wave radars need to integrate large-scale transceiver channels, typically 12 transmit and 16 receive. However, due to factors such as chip heat dissipation and cost, the current chip technology level is difficult to support the number of transceiver channels required for a single chip to integrate a 4D millimeter-wave radar. Therefore, multiple millimeter-wave radar chips need to be cascaded to expand the number of radar channels. However, most of the existing radar cascading solutions have large group delays after cascading.

[0004] For most cascade radars, the power dividers of the LO signals can be equal in phase, and have good isolation, but most of the group delay differences are large, within 5ps. However, for distance resolution of no more than 0.2m, the group delay between LO signals in the required frequency band must not exceed 2 / 3ps. At this time, the previous design is far from meeting the requirements.

[0005] In modern radar systems, especially high-precision point cloud radar systems, the power divider is a key component for signal distribution and combination, and its performance directly affects the overall performance of the radar system. Therefore, the consistency of the power divider group delay is particularly important for the overall performance of the radar system. A smaller group delay plays an important role in the radar target positioning accuracy, multi-target resolution, and anti-interference performance. Summary of the invention

[0006] The present invention provides a device for improving the group delay of a point cloud radar LO signal power divider, which can effectively reduce the difference in group delay, optimize the group delay of the power divider from 4.23ps to 0.17ps, have good phase consistency, greatly improve the synchronization capability of the radar system, and improve the overall performance.

[0007] An embodiment of the present invention provides a device for improving the group delay of a power divider of a point cloud radar LO signal, wherein the device is arranged in a multi-layer PCB board, and the device comprises: a main chip, a plurality of radio frequency chips, a power divider, a multi-layer metal layer, a first strip transmission line, a second strip transmission line, a first signal hole, and a second signal hole;

[0008] The output end of the main chip is connected to the input end of the power divider through the first signal hole and the first strip transmission line located in the PCB board;

[0009] The multiple output ends of the power divider are respectively connected to the input ends of the multiple RF chips through multiple second signal holes and second strip transmission lines of equal length and phase located on the PCB board;

[0010] Periodic return holes are arranged on both sides of the first strip transmission line and the second strip transmission line, and a quasi-coaxial design is adopted at the end points of the strip transmission lines.

[0011] Preferably, the power divider is a one-to-two-to-four Wilkinson power divider, wherein the main power divider and the two-to-four power divider form an angle of 90°, and the two-to-four power divider and the main power divider are arranged in a mirror image.

[0012] Preferably, the four output ends of the two-to-four power divider are respectively connected to the input ends of the four RF chips through four second signal holes and four second strip transmission lines of equal length and phase located on the PCB board.

[0013] Preferably, the PCB board has 8 layers in total, and the first strip transmission line and the second strip transmission line are located on the third layer of the PCB board.

[0014] Preferably, the first layer of the PCB board is a copper layer, the second layer is a ground layer, the third layer is a signal layer, the fourth layer is a ground layer, the fifth layer is a power layer, the sixth layer is a signal layer, and the seventh and eighth layers are metal ground layers;

[0015] The power divider is located on the first metal layer, and a dielectric layer RO3003G2 with a thickness of 0.127mm is arranged between the first and second layers; a dielectric layer of prepreg is arranged between the second and third layers with a thickness of 0.087mm; a core board with a thickness of 0.272mm is arranged between the third and fourth layers, and a dielectric layer of prepreg is arranged between the fourth and fifth layers; a dielectric layer is arranged between the fifth and sixth layers; a dielectric layer of prepreg is arranged between the sixth and seventh layers; a dielectric layer of 0.127mm is arranged between the seventh and eighth layers, and the entire board is 1.6mm thick.

[0016] Preferably, the periodic reflow holes on both sides of the first strip transmission line and the second strip transmission line penetrate the third layer and the fourth layer of the PCB board to connect the metal grounds of the third layer and the fourth layer of the PCB board.

[0017] Preferably, the periodic return holes are arranged at equal intervals, are annular at the end points of the first strip-shaped transmission line and the second strip-shaped transmission line, and are arranged around the centers of the first signal hole and the second signal hole respectively.

[0018] Preferably, the first signal hole and the second signal hole are back-drilled from the eighth layer to the fourth layer of the PCB board.

[0019] Preferably, the first signal hole and the second signal hole adopt four large metal ground holes and three small metal ground holes to form a quasi-coaxial structure.

[0020] Preferably, the main chip and multiple radio frequency chips are arranged on the first layer of the PCB board.

[0021] An embodiment of the present invention provides a device for improving the group delay of a power divider for a point cloud radar LO signal. The device is arranged in a multi-layer PCB board and specifically includes: a main chip, multiple radio frequency chips, a power divider, multiple metal layers, a first strip transmission line, a second strip transmission line, a first signal hole and a second signal hole. The output end of the main chip passes through the first signal hole and the first strip transmission line located in the PCB board to be connected to the input end of the power divider; multiple output ends of the power divider respectively pass through multiple second signal holes and second strip transmission lines of equal length and phase located in the PCB board to be connected to the input ends of the multiple radio frequency chips; periodic return holes are arranged on both sides of the first strip transmission line and the second strip transmission line, and a quasi-coaxial design is adopted at the end points of the strip transmission lines. In practical applications, due to limited space, the LO signal power divider group delay device provided in the embodiment of the present invention, through the LO signal routing design, makes the local oscillator distribution length mainly through the internal stripline layer, microstrip to stripline design, power division network partial grounding hole design, periodic return holes are distributed along both sides of the strip transmission line, which can effectively reduce the difference in group delay. In actual production design, the power division strip network group delay is successfully improved from 4.23ps to 0.17ps, which greatly improves the overall performance of the point cloud radar and improves the stability and reliability of the system. The present invention has a simple structure, low cost, small size, and is easy to process and manufacture, and has important engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a simulation curve of the group delay of the power divider of the point cloud radar LO signal in the prior art;

[0023] Figure 2 is a schematic diagram of the structure of a point cloud radar LO signal power splitter in an embodiment of the present invention;

[0024] Figure 3 It is a phase simulation curve for improving the group delay design of the point cloud radar LO signal power divider provided by the embodiment of the present invention;

[0025] Figure 4 It is a simulation curve of the group delay of the point cloud radar LO signal power divider provided by the embodiment of the present invention;

[0026] Figure 5 It is a simulation curve of the return loss of the point cloud radar LO signal power divider group delay improved by using the embodiment of the present invention;

[0027] Figure 6 It is a simulation curve of the amplitude of the point cloud radar LO signal power divider provided by the embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all 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.

[0029] It should be noted that in this specification, similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0030] See also Figure 1 , Figure 1 This is a simulation diagram of the group delay of the LO signal power divider of the point cloud radar in the prior art. It can be seen from the figure that before improvement, the group delay difference of the LO signal power divider within the required frequency range is 4.23ps, which is far from meeting the actual requirements. Because for most cascade radars, the LO signal power divider can be equal in phase and has good isolation, but the group delay difference is large, within 5ps. However, for the case where the distance resolution is not greater than 0.2m, the group delay between the LO signal power dividers at 25.5GHz must not exceed 2 / 3ps. At this time, the previous design is far from meeting the requirements.

[0031] In view of this, an embodiment of the present invention provides a design for improving the group delay of a point cloud radar LO signal power divider, so as to improve the problem of large group delay in the prior art, thereby improving the time synchronization capability and overall performance of the radar system.

[0032] See also Figure 2 , Figure 2 : is a schematic diagram of the structure of the point cloud radar LO signal power divider in an embodiment of the present invention. The device for improving the group delay of the point cloud radar LO signal power divider provided in an embodiment of the present invention is arranged in a multi-layer PCB board, and specifically includes: a main chip (not shown), multiple RF chips (not shown), a power divider 1, a multi-layer metal layer 2, a first strip transmission line 3, a second strip transmission line 4, a first signal hole 5 and a second signal hole 6; the output end of the main chip passes through the first signal hole 5 and the first strip transmission line 3 located in the PCB board to connect with the input end of the power divider 1, and the multiple output ends of the power divider 1 pass through multiple second signal holes 6 and the second strip transmission lines 4 of equal length and phase located in the PCB board to connect with the input ends of multiple RF chips, and periodic return holes 7 are arranged on both sides of the first strip transmission line 3 and the second strip transmission line 4, and a quasi-coaxial design is adopted at the end points of the strip transmission lines.

[0033] In some embodiments, the device for improving the group delay of the point cloud radar LO signal power divider is arranged in an 8-layer PCB board, wherein the main chip and multiple RF chips are located on the first layer of the PCB board, and the multiple RF chips can adopt a master-slave RF chip mode, wherein one of the RF chips is selected as the master chip, and the remaining RF chips are slave chips, the first layer of the PCB board is a copper layer, the second layer is a ground layer, the third layer is a signal layer, the fourth layer is a ground layer, the fifth layer is a power layer, the sixth layer is a signal layer, and the seventh and eighth layers are metal ground layers; the power divider 1 is located on the first metal layer, and the A dielectric layer RO3003G2 with a thickness of 0.127mm is arranged between the first and second layers; a dielectric layer which is a semi-cured sheet with a thickness of 0.087mm is arranged between the second and third layers; a core board with a thickness of 0.272mm is arranged between the third and fourth layers, and a dielectric layer which is a semi-cured sheet is arranged between the fourth and fifth layers; a dielectric layer is arranged between the fifth and sixth layers; a dielectric layer which is a semi-cured sheet is arranged between the sixth and seventh layers; a dielectric layer with a thickness of 0.127mm is arranged between the seventh and eighth layers, and the thickness of the entire board is 1.6mm.

[0034] The power divider 1 may be a one-to-two-to-four Wilkinson power divider, wherein the main power divider and the two-to-four power divider form an angle of 90°, and the two-to-four power divider and the main power divider are arranged in a mirror image. The four output ends of the two-to-four power divider are respectively connected to the input ends of the four RF chips through four second signal holes 6 and four second strip transmission lines 4 of equal length and phase located on the PCB board. The first strip transmission line 3 and the second strip transmission line 4 are located on the third layer of the PCB board. The periodic return holes 7 on both sides of the first strip transmission line 3 and the second strip transmission line 4 penetrate the third layer and the fourth layer of the PCB board to connect the metal grounds of the third layer and the fourth layer of the PCB board. The periodic return holes 7 are arranged at equal intervals, in a ring shape at the end points of the first strip transmission line 3 and the second strip transmission line 4 and are respectively arranged around the centers of the first signal hole 5 and the second signal hole 6. The first signal hole 5 and the second signal hole 6 are back-drilled from the eighth layer to the fourth layer of the PCB board. The first signal hole 5 and the second signal hole 6 use four large metal ground holes plus three small metal ground holes to form a quasi-coaxial structure.

[0035] The LO signal power divider group delay device provided by the embodiment of the present invention, through the LO signal routing design, makes the local oscillator distribution length mainly through the internal stripline layer, the microstrip to stripline design, the power division network partial grounding hole design, the periodic return hole distribution design along both sides of the strip transmission line, can effectively reduce the difference in group delay.

[0036] See also Figures 3 to 6 , Figure 3This is a phase simulation curve of the improved point cloud radar LO signal power divider group delay design provided by the embodiment of the present invention. It can be seen from the figure that the maximum phase difference is 0.04°, showing good phase consistency. Figure 4 This is a group delay simulation curve of the point cloud radar LO signal power divider provided by an embodiment of the present invention. It can be seen from the figure that the maximum difference is 0.17ps within the required frequency range. Figure 5 It is a simulation curve of the return loss of the point cloud radar LO signal power divider group delay design improved by using the embodiment of the present invention. The return loss is greater than 23dB in the required frequency band. Figure 6 This is an amplitude simulation curve of the improved point cloud radar LO signal power divider group delay design provided by the embodiment of the present invention. As can be seen from the figure, it shows good amplitude consistency.

[0037] The design of improving the group delay of the LO signal power divider of the point cloud radar provided by the embodiment of the present invention avoids mutual influence in stripline transmission, and greatly reduces the group delay of the LO signal power divider, so that the group delay is optimized from 4.23ps to 0.17ps within the required frequency range. The 25G~26G frequency band is less than 2 / 3ps, which meets the system index requirements very well, has good phase consistency, and the maximum phase difference is 0.04°, which greatly improves the synchronization capability between RF chips and the overall system performance, and has important engineering application value.

[0038] The present invention can effectively reduce the difference in group delay, and at the same time, has a simple structure, low cost, small size, and is easy to process and manufacture. The processing of the present invention can be completed by using mature PCB processing and assembly technology.

[0039] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A device for improving the group delay of the LO signal power divider of a point cloud radar, characterized in that: The device is arranged in a multi-layer PCB board, and comprises: a main chip, a plurality of radio frequency chips, a power divider, a multi-layer metal layer, a first strip transmission line, a second strip transmission line, a first signal hole and a second signal hole; The output end of the main chip is connected to the input end of the power divider through the first signal hole and the first strip transmission line located in the PCB board; The multiple output ends of the power divider are respectively connected to the input ends of the multiple RF chips through multiple second signal holes and second strip transmission lines of equal length and phase located on the PCB board; Periodic return holes are arranged on both sides of the first strip transmission line and the second strip transmission line, and a quasi-coaxial design is adopted at the end points of the strip transmission lines.

2. The device for improving the group delay of the point cloud radar LO signal power divider according to claim 1, characterized in that: The power divider is a one-to-two-to-four Wilkinson power divider, wherein the main power divider and the two-to-four power divider form an angle of 90°, and the two-to-four power divider and the main power divider are arranged in a mirror image.

3. The device for improving the group delay of the point cloud radar LO signal power divider according to claim 2, characterized in that: The four output ends of the two-to-four power divider are respectively connected to the input ends of the four RF chips through four second signal holes and four second strip transmission lines of equal length and phase located on the PCB board.

4. The device for improving the group delay of the point cloud radar LO signal power divider according to claim 1, characterized in that: The PCB board has 8 layers in total, and the first strip transmission line and the second strip transmission line are located on the third layer of the PCB board.

5. The device for improving the group delay of the point cloud radar LO signal power divider according to claim 1, characterized in that: The first layer of the PCB board is a copper layer, the second layer is a ground layer, the third layer is a signal layer, the fourth layer is a ground layer, the fifth layer is a power layer, the sixth layer is a signal layer, and the seventh and eighth layers are metal ground layers; The power divider is located on the first metal layer, and a dielectric layer RO3003G2 with a thickness of 0.127mm is arranged between the first and second layers; a dielectric layer of prepreg is arranged between the second and third layers with a thickness of 0.087mm; a core board with a thickness of 0.272mm is arranged between the third and fourth layers, and a dielectric layer of prepreg is arranged between the fourth and fifth layers; a dielectric layer is arranged between the fifth and sixth layers; a dielectric layer of prepreg is arranged between the sixth and seventh layers; a dielectric layer of 0.127mm is arranged between the seventh and eighth layers, and the entire board is 1.6mm thick.

6. The device for improving the group delay of the point cloud radar LO signal power divider according to claim 4, characterized in that: The periodic reflow holes on both sides of the first strip transmission line and the second strip transmission line penetrate the third layer and the fourth layer of the PCB board to connect the metal grounds of the third layer and the fourth layer of the PCB board.

7. The device for improving the group delay of the point cloud radar LO signal power divider according to claim 6, characterized in that: The periodic return holes are arranged at equal intervals, are annular at the end points of the first strip-shaped transmission line and the second strip-shaped transmission line, and are arranged around the centers of the first signal hole and the second signal hole respectively.

8. The device for improving the group delay of the point cloud radar LO signal power divider according to claim 4, characterized in that: The first signal hole and the second signal hole are back-drilled from the eighth layer to the fourth layer of the PCB board.

9. The device for improving the group delay of the point cloud radar LO signal power divider according to claim 4, characterized in that: The first signal hole and the second signal hole adopt four large metal ground holes and three small metal ground holes to form a quasi-coaxial structure.

10. The device for improving the group delay of the point cloud radar LO signal power divider according to claim 1, characterized in that: The main chip and multiple radio frequency chips are arranged on the first layer of the PCB board.

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