Microwave laser composite antenna off-axis tracking method suitable for deep space exploration

Abstract

The invention discloses a microwave laser composite antenna off-axis tracking method suitable for deep space exploration, and relates to the field of spaceflight deep space exploration. According to the method, Ka frequency band link angle tracking is completed firstly, and then a laser link is guided to be captured and tracked rapidly. Microwave link wave beam off-axis tracking is adopted, and simultaneous real-time target tracking of a microwave link and a laser link is achieved; the Ka beam is used for guiding the laser beam to rapidly capture and track, so that the laser beam coarse tracking robustness is improved, and the capture time is reduced; after the laser link finishes fine tracking, the system performs target tracking by using laser beam tracking, and compared with microwave Ka beam tracking, the tracking precision is higher; by using microwave link wave beam off-axis tracking, the problem that microwave link wave beams and laser link wave beams cannot be simultaneously aligned with a target due to inconsistent directions of a microwave electric axis and a laser optical axis is avoided. The scheme is simple and easy to realize, and can be directly applied to the existing integrated antenna.

Description

Technical Field

[0001] The present invention relates to the field of aerospace deep space exploration, and particularly to an off-axis tracking method for a microwave laser composite antenna applicable to deep space exploration, which can be used for target tracking of a microwave laser composite link of a super-large aperture antenna in deep space exploration. Background Technique

[0002] In the field of aerospace deep space exploration, the microwave laser integrated measurement and control communication technology can solve the bottleneck problem of high-capacity data transmission and is an important research direction for future deep space exploration. One of the technical difficulties in a microwave laser integrated measurement and control communication system is to achieve simultaneous real-time target tracking of a microwave link and a laser link. Especially for a deep space large aperture antenna, the Ka link beam is relatively narrow, about 0.02 degrees, and the laser antenna beam is narrower than the Ka beam. When the satellite target moves, the microwave link and the laser link need to simultaneously align with the target for tracking to complete the measurement and control communication of the two links, which is technically difficult. Due to the influence of antenna installation errors, gravity, atmospheric refraction, etc., there is a small deviation in the pointing consistency between the electrical axis of the microwave link and the optical axis of the laser link. When the antenna points to different angles, the pointing deviation between the electrical axis of the microwave link and the optical axis of the laser link will also change. Therefore, it is necessary to study the problem of simultaneous target tracking of the microwave link and the laser link of a deep space large aperture antenna. Summary of the Invention

[0003] In view of this, the present invention provides an off-axis tracking method for a microwave laser composite antenna applicable to deep space exploration. The present invention can achieve simultaneous real-time target tracking of a microwave link and a laser link in a microwave laser integrated measurement and control communication system, and the present invention has the characteristics of high tracking accuracy and high stability.

[0004] The object of the present invention is achieved as follows:

[0005] An off-axis tracking method for a microwave laser composite antenna applicable to deep space exploration, which is applied to a microwave and optical integrated antenna, wherein the microwave link frequency band is the Ka band, the laser link wavelength band is the 1550 nm band, and the microwave and laser links share a set of servo tracking equipment; the method includes the following steps:

[0006] Step 1, initialize the pointing of the servo tracking equipment, point the microwave antenna beam to the satellite target area, so that the target is within the coverage range of the Ka beam;

[0007] Step 2, detect the phase difference between the sum path and the difference path through the Ka link tracking receiver of the microwave antenna to complete the sum-difference path phase calibration;

[0008] Step 3, detect the azimuth voltage error and elevation voltage error of the microwave antenna, transmit the angular error information to the servo tracking equipment, adjust the pointing of the microwave antenna, and adjust the azimuth voltage error and elevation voltage error to approach 0, so that the target is at the center of the Ka beam to complete the Ka link angular tracking;

[0009] Step 4: Use the Ka link tracking result to guide the laser link tracking to make the laser beam cover the satellite target;

[0010] Step 5: Guide the laser link through the microwave link to achieve acquisition and tracking;

[0011] Step 6: After the laser beam is aligned with the target, the servo tracking device receives the angular error information of the laser link and tracks the target through the laser link.

[0012] Furthermore, the coarse tracking range of the laser link is 350 μrad.

[0013] Furthermore, in Step 5, when there is a deviation in the alignment error between the electrical axis of the microwave link and the optical axis of the laser link, resulting in the target not being able to be simultaneously at the center of the two-axis beam, adjust the microwave beam to offset by 1 / 20 to 1 / 4 of the microwave beam width for off-axis tracking to guide the laser link beam center to align with the target.

[0014] Furthermore, in Step 6, when the laser beam center is aligned with the target, if the microwave beam center deviates from the target position within the range of 1 / 20 to 1 / 4 of the microwave beam width, the microwave link tracking adopts off-axis tracking.

[0015] The present invention has the following advantages:

[0016] 1. The present invention uses the Ka beam to guide the laser beam tracking, improving the robustness of the laser beam coarse tracking and reducing the acquisition time.

[0017] 2. The present invention uses the laser beam tracking for target tracking, which has higher tracking accuracy compared with the microwave beam tracking.

[0018] 3. The present invention uses the microwave beam off-axis tracking to avoid the problem that the microwave beam and the laser beam cannot be simultaneously aligned with the target due to the inconsistent pointing of the microwave electrical axis and the laser optical axis.

[0019] 4. The solution of the present invention is simple and easy to implement, and can be directly applied to the existing microwave and optical integrated antenna. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic diagram of the composition of the microwave and optical integrated antenna in the embodiment of the present invention.

[0021] Figure 2 is a schematic diagram of the tracking principle when the microwave and laser beams are pointed in the same direction in the embodiment of the present invention.

[0022] Figure 3 is a schematic diagram of the off-axis tracking principle when there is a deviation in the pointing of the microwave and laser beams in the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention will be further described below in conjunction with the accompanying drawings and specific examples.

[0024] A method for off-axis tracking of a microwave-laser composite antenna applicable to deep space exploration is applied to a microwave and optical integrated antenna as shown in Figure 1 . The antenna includes a microwave link device and a laser link device. Among them, the microwave link device includes a Ka microwave antenna 1, a Ka feed 2, and a Ka downconverter 3; the laser link device includes a laser antenna 4, a CCD intensity detector 5, and a laser receiving link 6. The Ka microwave antenna 1 is used to receive space microwave signals, concentrate and transmit the microwave signals to the Ka feed 2 through a beam waveguide system. The Ka feed 2 is used to convert the space microwave signals into two electrical signals, a sum path and a difference path, amplify them, and transmit them to the Ka downconverter 3. The Ka downconverter 3 is used to downconvert the Ka-band signals to S-band signals and then downconvert them to 300M intermediate frequency signals. The 300M intermediate frequency signals include sum path and difference path signals and are transmitted to a tracking receiver 7. The laser antenna 4 receives space laser signals, performs optical path transmission and optoelectronic conversion, and transmits them to the CCD intensity detector 5. The CCD intensity detector 5 is used to detect the energy magnitude of the laser signals, convert the light beam into intensity value data at different pixel positions, and transmit them to the laser receiving link 6. The laser receiving link 6 is used to receive laser digital signals, convert them into protocol information that the tracking receiver 7 can recognize, and transmit them to the tracking receiver 7. The tracking receiver 7 is used to calculate the angular error information of the microwave link and the laser link. The servo tracking device 8 is used to receive the angular error information of the tracking receiver 7 and complete the antenna rotation to point to the target.

[0025] Taking the 35-meter deep space large-aperture antenna as an example, the Ka band is 26.5 GHz to 40 GHz. Calculated according to the frequency of 30 GHz, according to the antenna half-power beam width calculation formula , the half-power beam width of the 35-meter aperture antenna is 0.02 degrees. The Ka beam is relatively narrow, which is beneficial to guiding the laser link to capture. The 1550 nm band of the laser has less background light and low detected background noise in deep space, and it also has certain advantages in high-speed modulation, eye safety, etc.

[0026] The method specifically includes the following steps:

[0027] (1) The antenna servo tracking device initializes the pointing. According to the satellite orbit data information or other guiding information such as S-band and X-band pointing, the microwave antenna beam is pointed to the satellite target area so that the target is within the coverage range of the Ka beam.

[0028] (2) The Ka link tracking receiver of the microwave antenna detects the phase difference between the sum path and the difference path and completes the sum-difference path phase calibration.

[0029] (3) Detect the azimuth voltage error and elevation voltage error of the microwave antenna through the dual-channel angle tracking algorithm, transmit the angle error information to the antenna servo tracking device, adjust the pointing of the microwave antenna, and adjust the azimuth voltage error and elevation voltage error to approach 0, so that the target is at the center of the Ka beam, and complete the Ka link angle tracking. Refer to Figure 2 .

[0030] (4) Use the Ka link tracking result to guide the laser link tracking, reduce the rough tracking search range of the laser link. After the Ka link angle tracking is completed, the laser beam can cover the satellite target, and then switch to the acquisition and tracking of the laser link.

[0031] The half beam width of the Ka microwave link is about 0.02 degrees. After the Ka link completes the angle tracking, in order to be able to guide the laser link to complete the fast acquisition and tracking, the rough tracking range of the laser link is designed to be 0.02 degrees (about 350 μrad) to ensure that the target is covered within the laser beam.

[0032] (5) Realize the acquisition and tracking of the laser link through the microwave link guidance.

[0033] If there is a deviation in the alignment error between the electrical axis of the microwave link and the optical axis of the laser link, it will cause the target not to be at the center of the two-axis beam at the same time. In this case, when the microwave beam is aligned with the target, the laser fine tracking cannot be aligned with the target. At this time, adjust the microwave beam to offset by 1 / 20 - 1 / 4 of the beam width for off-axis tracking to guide the laser link beam center to align with the target.

[0034] (6) After the microwave link guides the laser link to complete the acquisition and tracking, the laser beam center is aligned with the target. Refer to Figure 2 , and the servo tracking device receives the laser link angle error information, and the target tracking is mainly based on the laser link tracking.

[0035] Since the laser link beam is narrower and the tracking accuracy is higher, when the laser link completes the fine tracking, the laser link tracking is mainly used, and the laser link controls the servo tracking device. When the electrical axis of the microwave link and the optical axis of the laser link point in the same direction, when the laser link beam center is aligned with the target, the microwave link beam center will also be aligned with the target. Refer to Figure 2 .

[0036] Due to the influence of antenna installation error, gravity, atmospheric refraction, etc., there is a small deviation in the alignment of the electrical axis of the microwave link and the optical axis of the laser link. When the antenna points to different angles, the alignment deviation between the electrical axis of the microwave link and the optical axis of the laser link will also change slightly. The microwave link beam deviating by 1 / 20 - 1 / 4 of the beam width basically does not affect the microwave link signal reception. Therefore, the microwave link uses off-axis tracking to ensure that the laser link beam center is aligned with the target. Refer to Figure 3 , Axis 1 represents the position of the microwave link beam center, and Axis 2 represents the position of the laser link beam center.

[0037] After the laser link completes self-tracking, the microwave link maintains off-axis tracking to track the target.

[0038] In the present invention, when the center of the laser beam is aligned with the target, the center of the microwave beam is offset from the target position within the range of 1 / 20 to 1 / 4 of the microwave beam width. The microwave link tracking adopts off-axis tracking and can offset the center of the microwave beam by 1 / 20 to 1 / 4 of the microwave beam width. At this time, the azimuth voltage error and the pitch voltage error no longer approach 0, but are superimposed with a relatively small voltage offset. The off-axis tracking has little impact on the received level of the microwave link, does not affect the measurement and control communication of the microwave link, and at the same time can ensure that the laser link is aligned with the target for measurement and control communication, giving priority to ensuring high-rate data transmission of the laser link.

[0039] In summary, the present invention first completes the angle tracking of the Ka-band link, and then guides the laser link to quickly capture and track, improving the robustness of the coarse tracking of the laser beam and reducing the capture time; adopts off-axis tracking of the microwave link beam to achieve simultaneous real-time target tracking of the microwave link and the laser link; after the laser link completes fine tracking, uses the laser beam tracking for target tracking, which has higher tracking accuracy compared with the microwave Ka beam tracking; uses off-axis tracking of the microwave link beam to avoid the problem that the microwave beam and the laser beam of the microwave link cannot be simultaneously aligned with the target due to the inconsistent pointing of the microwave electrical axis and the laser optical axis.

Claims

1. A method for off-axis tracking of a microwave-laser composite antenna applicable to deep space exploration, which is applied to an integrated microwave and optical antenna, wherein, The microwave link frequency band is the Ka band, the laser link wavelength band is the 1550 nm band, and the microwave and laser links share a set of servo tracking equipment; it is characterized by including the following steps: Step 1, initialize the pointing of the servo tracking equipment, point the microwave antenna beam to the satellite target area, and make the target within the coverage of the Ka beam; Step 2, detect the phase difference between the sum path and the difference path through the Ka link tracking receiver of the microwave antenna to complete the sum-difference path phase calibration; Step 3, detect the azimuth voltage error and elevation voltage error of the microwave antenna, transmit the angular error information to the servo tracking equipment, adjust the pointing of the microwave antenna, and adjust the azimuth voltage error and elevation voltage error to approach 0, so that the target is at the center of the Ka beam to complete the Ka link angular tracking; Step 4, use the Ka link tracking result to guide the laser link tracking to make the laser beam cover the satellite target; Step 5, use the microwave link to guide the laser link to achieve acquisition and tracking; Step 6, after the laser beam is aligned with the target, the servo tracking equipment receives the laser link angular error information and tracks the target through the laser link.

2. The off-axis tracking method of a microwave laser composite antenna applicable to deep space exploration according to claim 1, wherein The coarse tracking range of the laser link is 350 μrad.

3. A method for off-axis tracking of a microwave laser composite antenna applicable to deep space exploration according to claim 1, characterized in that In Step 5, when there is a deviation in the alignment error between the electrical axis of the microwave link and the optical axis of the laser link, resulting in the target not being able to be at the center of the two-axis beams at the same time, adjust the microwave beam to offset by 1 / 20 to 1 / 4 of the microwave beam width for off-axis tracking and guide the laser link beam center to align with the target.

4. The off-axis tracking method of the microwave laser composite antenna applicable to deep space exploration according to claim 1, characterized in that In Step 6, when the laser beam center is aligned with the target, if the microwave beam center is offset from the target position within the range of 1 / 20 to 1 / 4 of the microwave beam width, the microwave link tracking adopts off-axis tracking.

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