A multi-channel radar system and an external calibration method

Abstract

The present application relates to a kind of multi-channel radar system external calibration method, comprising the following steps: adapter tool is fixedly connected on the calibration surface of radar antenna, the plane position of radar antenna calibration surface and adapter tool calibration surface is measured by measuring instrument, the inherent relative position relationship of both is solved;Radar antenna and adapter tool are combined and loaded into cabin;The position of adapter tool calibration surface and external calibration source is measured respectively using measuring instrument, the relative position of both is solved, and external calibration source position is adjusted until external calibration source is located at the mechanical zero of antenna;The inter-channel phase difference under the external calibration and internal calibration of radar receiver is analyzed, and the insertion phase is solved.The present application realizes the measurable of antenna calibration surface by the conversion of adapter tool, thereby carries out external calibration to multi-channel radar system, and improves the measurement accuracy of radar system.

Description

Technical Field

[0001] This invention relates to the field of multi-channel radar technology, and in particular to a multi-channel radar system and an external calibration method. Background Technology

[0002] When multi-channel radar systems perform multi-channel fusion measurements, such as digital beamforming and interferometry, their measurement performance is affected by various parameter errors. These errors primarily originate from instrument errors, transmission errors, and data processing errors. Since these errors have different sources and varying impacts, corresponding measures must be taken to mitigate or compensate for them to improve the overall system performance. Typically, internal and external calibration methods are employed to calibrate the phase differences between channels in the system's receiving link and to compensate for these differences, thereby improving measurement accuracy.

[0003] Regarding patents on external calibration, the patent "External Calibration Method for Spaceborne InSAR System" (Publication No.: CN103364766A) by Wang Yu, Ding Chibiao, and Liang Xingdong of the Institute of Electronics, Chinese Academy of Sciences, discloses an external calibration method for a spaceborne InSAR system. This external calibration method includes: obtaining average sea level height data by removing time-varying factors from sea level height data measured by a satellite altimeter; obtaining sea level height data measured by the spaceborne InSAR system from ocean image pairs with preset time and spatial distributions and uncalibrated interferometric parameters; simulating and calculating the sea level height changes caused by time-varying factors other than propagation under preset time and spatial distribution conditions; obtaining time-varying synthetic sea level height data from the average sea level height and the sea level height changes caused by time-varying factors other than propagation; and using the time-varying synthetic sea level height data as standard data to correct the sea level height data measured by the spaceborne InSAR system, thereby achieving the calibration of the spaceborne InSAR system. This patent uses time-varying synthetic sea surface height data as standard data to correct the sea surface height data measured by the spaceborne InSAR system, without involving phase calibration. The patent by Qiao Ming, Liang Xingdong, Ding Chibiao, Zhang Peijie, and Han Bing of the Institute of Electronics, Chinese Academy of Sciences—"An Active External Calibrator and Calibration Method for Broadband Synthetic Aperture Radar" (Publication No.: CN101082670)—invents a new broadband synthetic aperture radar external calibrator, improving the gain of the active calibration transceiver system, thus significantly improving the accuracy of external calibration even in complex, high-altitude clutter conditions. This patent also does not involve phase calibration when the antenna is out of line of sight. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a multi-channel radar system and an external calibration method for the antenna cover. This method performs external calibration on the radar system when the antenna surface is not within the line of sight, thereby ensuring the altitude measurement accuracy of the entire radar system. The pointing accuracy after calibration is better than 0.05°.

[0005] An external calibration method for a multi-channel radar system, characterized in that the calibration surface of the radar antenna is parallel to the radiating surface, and the mechanical null point of the antenna is the direction of the perpendicular bisector of the radiating surface. This calibration method includes the following steps:

[0006] S1. Fix the adapter fixture to the calibration surface of the radar antenna, measure the planar position of the radar antenna calibration surface and the adapter fixture calibration surface using a measuring instrument, and calculate the inherent relative positional relationship between the two.

[0007] S2. Assemble the radar antenna and adapter into the cabin, and ensure that the calibration surface of the adapter and the external calibration source are both within the visible range of the measuring instrument.

[0008] S3. Use measuring instruments to measure the positions of the adapter tool calibration surface and the external calibration source respectively, calculate their relative positions, and adjust the position of the external calibration source until the external calibration source is located at the mechanical zero position of the antenna;

[0009] S4. Analyze the inter-channel phase difference under the external calibration method of the radar receiver, analyze the inter-channel phase difference under the internal calibration method, and calculate the inserted phase.

[0010] Preferably, step S1 includes the following: measuring instruments measure multiple designated points on the adapter tool calibration surface and the antenna calibration surface; fitting the planes of the two planes based on the measured designated points; calculating the perpendicular bisectors of the two planes; and calculating the first included angle θ between the two perpendicular bisectors on the radar antenna H-plane. H1 The second included angle θ on the E-plane of the radar antenna E1 .

[0011] Preferably, step S3 includes the following: measuring instruments measure multiple designated points on the adapter tooling calibration surface and the external calibration source; fitting the planes of the two planes based on the measured designated points; calculating the perpendicular bisectors of the two planes; and calculating the third included angle θ between the two perpendicular bisectors on the radar antenna H-plane. H2 The fourth included angle θ on the E plane of the radar antenna E2 Move the external standard source position until the third included angle θ. H2 Equal to the first included angle θ H1 and the fourth included angle θ E2 Equal to the second included angle θ E1 .

[0012] Preferably, the insertion phase in S4 is the phase difference between the external calibration link channel and the internal calibration link channel.

[0013] Preferably, the calibration signal generated by the radar body enters the antenna through the calibration channel and is coupled to the antenna's receiving channel. It is then connected to the radar body receiver via a connecting cable. The phase difference of the internal calibration link channel is φ' = (φ' 11 -φ' 1n )+(φ 21 -φ 2n )+(φ 31 -φ 3n ), where φ' 11 Indicates the phase of channel 1 of the internal calibration link antenna, φ' 1n Indicates the n-channel phase and φ of the internal calibration link antenna. 21 This indicates the phase and φ introduced by the cable connecting antenna channel 1 and radar receiver channel 1. 2n This indicates the phase and φ introduced by the cable connecting the antenna n-channel and the radar receiver n-channel. 31 This indicates the phase of channel 1 inside the radar receiver, φ 3n This indicates the phase of the n-channel internal receiver of the radar body; the echo from the external calibration source is transmitted through space into the antenna receiving channel and then enters the radar body through a connecting cable; the phase difference of the external calibration link channel is φ = (φ 01 -φ 0n )+(φ 11 -φ 1n )+(φ 21 -φ 2n )+(φ 31 -φ 3n ), where φ 01 This indicates the phase and φ of the signal brought into antenna channel 1 by the signal after spatial radiation and antenna cover in the external calibration link. 0n This indicates the phase and φ of the signal in the external calibration link after spatial radiation and antenna cover to the antenna n-channel. 11 Indicates the phase of channel 1 of the external calibration link antenna, φ 1n Indicates the phase of the n-channel antenna of the external calibration link, φ 21 This indicates the phase and φ introduced by the cable connecting antenna channel 1 and radar receiver channel 1. 2n This indicates the phase and φ introduced by the cable connecting the antenna n-channel and the radar receiver n-channel. 31 This indicates the phase of channel 1 inside the radar receiver, φ 3n This indicates the phase of the n-channel inside the radar receiver.

[0014] Preferably, the flatness σ1 of the antenna calibration surface is better than 0.01°; the flatness σ2 of the adapter tool calibration surface is better than 0.01°.

[0015] To implement the above calibration method, this invention provides a multi-channel radar system, comprising: an external calibration source; an antenna cover plate fixed to the cabin; a multi-channel radar antenna disposed within the cabin for transmitting and receiving signals; an adapter fixture connected to the calibration surface of the multi-channel radar antenna; a measuring instrument for measuring the positions of the external calibration source, the multi-channel radar antenna, and designated points on the adapter fixture; and a radar receiver comprising multiple receiving channels and a calibration signal, connected to the multi-channel radar antenna.

[0016] This invention primarily enables the measurement of the antenna calibration surface by using an adapter when the antenna surface is not within the line of sight, thereby performing external calibration on a multi-channel radar system and improving the measurement accuracy of the radar system. Attached Figure Description

[0017] Figure 1 This is a structural block diagram of the present invention. Detailed Implementation

[0018] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a further detailed explanation of the multi-channel radar system and external calibration method proposed in this invention. Figure 1 As shown, this invention provides a multi-channel radar system, comprising: an external calibration source; an antenna cover plate fixed to the cabin for thermal protection of the multi-channel antenna; a multi-channel radar antenna disposed at a certain distance from the antenna cover plate on the cabin for transmitting and receiving signals; an adapter fixture connected to the calibration surface of the multi-channel radar antenna; a measuring instrument for measuring the positions of the external calibration source, the multi-channel radar antenna, and designated points on the adapter fixture; and a radar receiver comprising multiple receiving channels and a calibration signal, wherein each receiving channel and the calibration signal are connected to each channel of the multi-channel radar antenna via connecting cables.

[0019] Using the aforementioned multi-channel radar system, this invention provides a method for external calibration of the antenna cover of a multi-channel radar system. To implement this calibration method, the beam center direction of the multi-channel antenna is first defined: the E-plane is the point of maximum antenna gain, and the H-plane is the direction where the theoretical phase difference between channels is equal to 0. That is, for an antenna without beam pointing offset, the perpendicular bisector of the antenna aperture (mechanical null position) is the null position. Simultaneously, the calibration surface and the radiating surface of the radar antenna are parallel, and the mechanical null position of the antenna is the perpendicular bisector of the radiating surface, which is also the perpendicular bisector of the calibration surface. This calibration method includes the following steps:

[0020] S1. Fix the adapter fixture to the calibration surface of the radar antenna. Measure the planar positions of the radar antenna calibration surface and the adapter fixture calibration surface using a measuring instrument, and calculate their inherent relative positional relationship. The flatness of the antenna calibration surface σ1 is better than 0.01°, the flatness of the adapter fixture calibration surface σ2 is better than 0.01°, the adapter fixture has good rigidity, and the deformation error σ3 is less than 0.001°.

[0021] S2. Assemble the radar antenna and adapter into the cabin, and ensure that the calibration surface of the adapter and the external calibration source are both within the visible range of the measuring instrument.

[0022] S3. Use measuring instruments to measure the positions of the adapter tool calibration surface and the external calibration source respectively, calculate the relative positions of the two planes, and adjust the position of the external calibration source until the external calibration source is located at the mechanical zero position of the antenna;

[0023] S4. Analyze the inter-channel phase difference under the external calibration method of the radar receiver, analyze the inter-channel phase difference under the internal calibration method, and calculate the inserted phase.

[0024] Specifically, taking the measuring instrument as the origin of the coordinate system, the measuring instrument measures the designated points on the calibration surface of the transition tooling, and the measured points are recorded as A1(x1,y1,z1), A2(x2,y2,z2), ... A n (x n ,y n ,z n ), measure the specified points on the antenna calibration surface, and record the measured points as B1(x1,y1,z1), B2(x2,y2,z2), ... B n (x n ,y n ,z n After fitting the plane, the perpendicular bisector λ of the two measured planes is calculated. A , λ B Solve for the first angle θ between the two perpendicular bisectors on the H-plane of the radar antenna. H1 The second included angle θ on the E-plane of the radar antenna E1 .

[0025] The radar antenna and adapter fixture are assembled in the bay. Using a measuring instrument as the origin, the measuring instrument measures designated points on the adapter fixture's calibration surface. These measured points are denoted as C1(x1,y1,z1), C2(x2,y2,z2), ..., C... n (x n ,y n ,z n Place the external calibration source in a suitable location, measure the designated points of the external calibration source, and record the measured points as D1(x1,y1,z1), D2(x2,y2,z2), ... D n (x n ,y n ,z n After fitting the plane, the perpendicular bisectors λ of the two measured surfaces are calculated. C , λ D Solve for the third angle θ between the two perpendicular bisectors on the H-plane of the radar antenna. H2 The fourth included angle θ on the E plane of the radar antenna E2The location of the calibration source is analyzed using the measurement results.

[0026] If θ H1 =θ H2 θ E1 =θ E2 This means that the external calibration source is now at the theoretical antenna mechanical null position, and subsequent operations can proceed. If this is not the case, adjust the position of the external calibration source appropriately based on the results, and remeasure its designated point until θ is satisfied. H1 =θ H2 θ E1 =θ E2 The positional accuracy is 1mm.

[0027] In summary, it is necessary to reasonably control the errors of different influencing factors in the antenna cover calibration process based on the accuracy of the antenna cover calibration. These factors include the flatness of the antenna calibration surface σ1, the flatness of the adapter tool calibration surface σ2, the angular change caused by deformation after the adapter tool and antenna are installed σ3, and the error σ of the measuring instrument in measuring the plane angle. ma The error σ in the measurement position of the measuring instrument mp According to the error propagation formula,

[0028] The flatness and rigidity of the antenna calibration surface and the adapter tooling calibration surface, as well as any changes after fixing, should be controlled to be as small as possible, less than 1 / 4 of the calibration requirements. The introduced adapter tooling error is...

[0029] Specifically, in S4, the phase difference between channels measured under external calibration mode is as follows: During external calibration, the echo from the external calibration source is transmitted through space into the antenna receiving channel and then connected to the radar body via a connecting cable. The phase difference between the external calibration link channels is φ = (φ... 01 -φ 0n )+(φ 11 -φ 1n )+(φ 21 -φ 2n )+(φ 31 -φ 3n ). Measure the channel phase difference in internal calibration mode. Where φ 01 This indicates the phase and φ of the signal brought into antenna channel 1 by the signal after spatial radiation and antenna cover in the external calibration link. 0n This indicates the phase and φ of the signal brought into the antenna n-channel by the signal after spatial radiation and antenna cover in the external calibration link. 11 Indicates the phase of channel 1 of the external calibration link antenna, φ 1n Indicates the phase of the n-channel antenna of the external calibration link, φ 21 This indicates the phase and φ introduced by the cable connecting antenna channel 1 and radar receiver channel 1. 2n This indicates the phase and φ introduced by the cable connecting the antenna n-channel and the radar receiver n-channel.31 This indicates the phase of channel 1 inside the radar receiver, φ 3n This indicates the phase of the n-channel inside the radar receiver.

[0030] During internal calibration, the calibration signal generated by the radar itself enters the antenna through the calibration channel and is coupled to the antenna's receiving channel, then connected to the radar receiver via a connecting cable. The phase difference of the internal calibration link channel is φ'=(φ' 11 -φ' 1n )+(φ 21 -φ 2n )+(φ 31 -φ 3n ). Calculate the insertion phase difference; subtract the phase differences between the inner and outer calibration links: φ - φ' = (φ 01 -φ 0n )+(φ 11 -φ 1n )-(φ' 11 -φ' 1n ), which is the phase that needs to be inserted. Where φ' 11 Indicates the phase of channel 1 of the internal calibration link antenna, φ' 1n Indicates the n-channel phase and φ of the internal calibration link antenna. 21 This indicates the phase and φ introduced by the cable connecting antenna channel 1 and radar receiver channel 1. 2n This indicates the phase and φ introduced by the cable connecting the antenna n-channel and the radar receiver n-channel. 31 This indicates the phase of channel 1 inside the radar receiver, φ 3n This indicates the phase of the n-channel inside the radar receiver.

[0031] Therefore, by writing the required compensation phase into the radar body, the phase difference caused by factors such as the non-parallelism between the radiating surface and the calibration surface due to antenna processing and assembly, the inconsistency in the spacing between the antenna cover and the antenna after mounting, and the influence of the characteristics of the antenna cover itself can be solved, thereby improving the measurement accuracy of the radar system.

[0032] This invention primarily enables the measurement of the antenna calibration surface by using an adapter when the antenna surface is not within the line of sight, thereby performing external calibration on a multi-channel radar system and improving the measurement accuracy of the radar system.

[0033] The adapter tooling described in this invention has excellent rigidity, parallelism, and flatness, and will not introduce measurement errors caused by its own installation or deformation under stress in the above calibration method.

[0034] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for external calibration of a multi-channel radar system, characterized in that, The calibration surface of the radar antenna is parallel to the radiating surface, and the mechanical null point of the antenna is the direction of the perpendicular bisector of the radiating surface. This calibration method includes the following steps: S1. Fix the adapter fixture to the calibration surface of the radar antenna, measure the planar position of the radar antenna calibration surface and the adapter fixture calibration surface using a measuring instrument, and calculate the inherent relative positional relationship between the two. S2. Assemble the radar antenna and adapter into the cabin, and ensure that the calibration surface of the adapter and the external calibration source are both within the visible range of the measuring instrument. S3. Use measuring instruments to measure the positions of the adapter tool calibration surface and the external calibration source respectively, calculate their relative positions, and adjust the position of the external calibration source until the external calibration source is located at the mechanical zero position of the antenna; S4. Analyze the inter-channel phase difference under the external calibration method of the radar receiver, analyze the inter-channel phase difference under the internal calibration method, and calculate the inserted phase. S1 includes the following: measuring instruments measure multiple designated points on the adapter tool calibration surface and the antenna calibration surface; fitting the planes of the two planes based on the measured designated points; calculating the perpendicular bisectors of the two planes; and calculating the first included angle between the two perpendicular bisectors on the radar antenna H-plane. The second included angle on the E-plane of the radar antenna ; S3 includes the following: measuring instruments measure multiple designated points on the adapter tool calibration surface and the external calibration source; fitting the planes of the two planes based on the measured designated points; calculating the perpendicular bisectors of the two planes; and calculating the third included angle between the two perpendicular bisectors on the H-plane of the radar antenna. The fourth included angle on the E-plane of the radar antenna ; Move the external standard source position until the third angle. equal to the first included angle and the fourth angle equal to the second included angle .

2. The external calibration method for a multi-channel radar system as described in claim 1, characterized in that, The insertion phase in S4 is the phase difference between the external calibration link channel and the internal calibration link channel.

3. The external calibration method for a multi-channel radar system as described in claim 2, characterized in that, The calibration signal generated by the radar body enters the antenna through the calibration channel and is coupled to the antenna's receiving channel. It is then connected to the radar receiver via a connecting cable. The phase difference of the internal calibration link channel is... ,in Indicates the phase of channel 1 of the internal calibration link antenna. Indicates the phase of the n-channel antenna in the internal calibration link. This indicates the phase carried by the cable connecting antenna channel 1 and radar receiver channel 1. This indicates the phase carried by the cable connecting the antenna n-channel and the radar receiver n-channel. This indicates the phase of channel 1 inside the radar receiver. This indicates the phase of the n-channel internal receiver of the radar body; the echo from the external calibration source is transmitted through space into the antenna receiving channel and then enters the radar body through a connecting cable; the phase difference of the external calibration link channel is... ,in This indicates the phase of the signal in the external calibration link after spatial radiation and the antenna cover, which is then introduced into antenna channel 1. This indicates the phase of the signal in the external calibration link after spatial radiation and the antenna cover, which is then introduced into the antenna n-channel. Indicates the phase of channel 1 of the external calibration link antenna. This indicates the phase of the n-channel antenna in the external calibration link.

4. The external calibration method for a multi-channel radar system as described in claim 1, characterized in that, The flatness of the antenna calibration surface Better than 0.01°; Flatness of the calibration surface of the adapter tool Better than 0.01°.

5. A multi-channel radar system for implementing the external calibration method for a multi-channel radar system as described in any one of claims 1 to 4, characterized in that, Include: External source of the school; Antenna cover plate, fixed to the cabin; A multi-channel radar antenna is installed inside the cabin for transmitting and receiving signals; The adapter is connected to the calibration surface of the multi-channel radar antenna; Measuring instruments are used to measure the position of designated points on external standard calibration sources, multi-channel radar antennas, and adapter fixtures; The radar receiver, which includes multiple receiving channels and calibration signals, is connected to a multi-channel radar antenna.

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