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

Abstract

The present invention discloses a microwave laser composite antenna off-axis tracking method suitable for deep space exploration, which relates to the field of aerospace deep space exploration. The present invention first completes the Ka-band link angle tracking, and then guides the laser link to quickly capture and track. By adopting microwave link beam off-axis tracking, simultaneous real-time target tracking of the microwave link and the laser link is realized; the Ka beam is used to guide the laser beam to quickly capture and track, which improves the robustness of the laser beam coarse tracking and reduces the capture time; after the laser link completes the fine tracking, the system uses laser beam tracking to track the target, which has higher tracking accuracy than microwave Ka beam tracking; the microwave link beam off-axis tracking is used to avoid the problem that the microwave link beam and the laser link beam cannot be aimed at the target at the same time due to the inconsistent pointing of the microwave electric axis and the laser optical axis. The solution of the present invention is simple, easy to implement, and can be directly applied to existing integrated antennas.

Description

Technical Field

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

[0002] In the field of deep space exploration, integrated microwave-laser measurement, control, and communication technology can resolve the bottleneck problem of high-capacity data transmission and is an important research direction for future deep space exploration. Achieving simultaneous real-time target tracking for both microwave and laser links in a microwave-laser integrated measurement, control, and communication system is a technical challenge, especially since the Ka link beam of a large-aperture deep space antenna is relatively narrow, approximately 0.02 degrees, and the laser antenna beam is even narrower than the Ka beam. When a satellite target is in motion, both the microwave and laser links must be simultaneously aligned to track the target, completing measurement, control, and communication for both links. This presents a significant technical challenge. Due to antenna installation errors, gravity, atmospheric refraction, and other factors, there are slight deviations in the pointing consistency between the microwave link's electrical axis and the laser link's optical axis. These deviations also change when the antennas are pointed at different angles. Therefore, it is necessary to study the simultaneous target tracking of microwave and laser links using large-aperture deep space antennas. Summary of the Invention

[0003] In light of this, the present invention provides a microwave laser composite antenna off-axis tracking method suitable for deep space exploration. This method enables simultaneous real-time target tracking of both microwave and laser links within a microwave laser integrated measurement, control, and communication system, and exhibits high tracking accuracy and stability.

[0004] The object of the present invention is achieved like this:

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

[0006] Step 1: The servo tracking device initializes the pointing direction and points the microwave antenna beam toward the satellite target area so that the target is within the coverage of the Ka beam.

[0007] Step 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 and difference path phase calibration;

[0008] Step 3: Detect the azimuth voltage error and elevation voltage error of the microwave antenna, transmit the angle error information to the servo tracking device, adjust the microwave antenna pointing direction, adjust the azimuth voltage error and elevation voltage error to be close to 0, so that the target is in the center of the Ka beam, and complete the Ka link angle tracking;

[0009] Step 4: Use the Ka link tracking result to guide the laser link tracking so that the laser beam covers the satellite target;

[0010] Step 5: Use the microwave link to guide the laser link to achieve capture and tracking;

[0011] Step 6: After the laser beam is aligned with the target, the servo tracking device receives the laser link angle error information 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 consistency error between the microwave link electrical axis and the laser link optical axis, resulting in the target not being able to be at the center of the two-axis beam at the same time, the microwave beam is adjusted to offset 1 / 20 to 1 / 4 of the microwave beam width, and off-axis tracking is performed 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 offsets the target position within a 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 utilizes Ka beam to guide laser beam tracking, thereby improving the robustness of laser beam coarse tracking and reducing the acquisition time.

[0017] 2. The present invention utilizes laser beam tracking to track targets, which has higher tracking accuracy than microwave beam tracking.

[0018] 3. The present invention utilizes off-axis tracking of the microwave beam 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 electric 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 existing microwave and optical integrated antennas. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0021] Figure 2 Schematic diagram of tracking principle when microwave and laser beams point in the same direction according to an embodiment of the present invention.

[0022] Figure 3 It is a schematic diagram of the off-axis tracking principle when the microwave and laser beams are pointing in a deviation manner in an embodiment of the present invention. DETAILED DESCRIPTION

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

[0024] A microwave laser composite antenna off-axis tracking method suitable for deep space exploration, such as Figure 1 The microwave and optical integrated antenna shown in the figure includes a microwave link device and a laser link device. 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 spatial microwave signals, concentrate the microwave signals through a beam waveguide system, and transmit them to the Ka feed 2. The Ka feed 2 is used to convert the spatial microwave signals into two electrical signals, a sum channel and a difference channel, amplify them, and transmit them to the Ka downconverter 3. The Ka downconverter 3 is used to downconvert the Ka-band signal to the S-band signal, and then downconvert it to a 300 MHz intermediate frequency signal. The 300 MHz intermediate frequency signal includes the sum channel and difference channel signals and is transmitted to the tracking receiver 7. The laser antenna 4 receives the spatial laser signal, performs optical transmission and photoelectric conversion, and transmits it to the CCD intensity detector 5. The CCD intensity detector 5 detects the energy of the laser signal, converts the beam into intensity value data at different pixel positions, and transmits it to the laser receiving link 6. Laser receiving link 6 receives digital laser signals, converts them into protocol information recognizable by tracking receiver 7, and transmits them to tracking receiver 7. Tracking receiver 7 calculates angular errors in the microwave and laser links. Servo tracking device 8 receives angular error information from tracking receiver 7 and enables the antenna to rotate toward the target.

[0025] Taking the D=35m deep space large aperture antenna as an example, the Ka band is 26.5GHz~40GHz, calculated based on the frequency of 30GHz, according to the antenna half-power beamwidth calculation formula The half-power beamwidth of the 35-meter antenna is 0.02 degrees. The narrow Ka beam facilitates guided laser link acquisition. The 1550nm laser band offers low background light and noise in deep space, and also offers advantages in high-speed modulation and eye safety.

[0026] The method specifically comprises the following steps:

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

[0028] (2) The microwave antenna Ka link tracking receiver detects the phase difference between the sum path and the difference path, and completes the sum and 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 microwave antenna pointing, adjust the azimuth voltage error and elevation voltage error to be close to 0, so that the target is in the center of the Ka beam, and complete the Ka link angle tracking. Figure 2 .

[0030] (4) The Ka link tracking results are used to guide the laser link tracking, reducing the coarse tracking search range of the laser link. After the Ka link angle tracking is completed, the laser beam can cover the satellite target and switch to the capture tracking of the laser link.

[0031] The half-beam width of the Ka microwave link is approximately 0.02 degrees. After the Ka link completes angular tracking, in order to guide the laser link to complete rapid capture and tracking, the coarse tracking range of the laser link is designed to be 0.02 degrees (approximately 350 μrad) to ensure that the target is covered within the laser beam.

[0032] (5) Capture and tracking are achieved by guiding the laser link through the microwave link.

[0033] If there is a misalignment between the microwave link's electrical axis and the laser link's optical axis, the target may not be centered on both beams. In this case, laser precision tracking cannot align with the target when the microwave beam is aligned. In this case, adjust the microwave beam offset by 1 / 20 to 1 / 4 of the beam width for off-axis tracking, guiding the laser link beam center to the target.

[0034] (6) After the microwave link guides the laser link to complete the capture and tracking, the center of the laser beam is aligned with the target, referring to Figure 2 ,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, after the laser link completes the fine tracking, the laser link tracking is the main focus, and the laser link controls the servo tracking equipment. When the microwave link electrical axis and the laser link optical axis point to the same direction, the laser link beam center will align with the target at the same time as the microwave link beam center. Figure 2 .

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

[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 laser beam center is aligned with the target, the microwave beam center is offset from the target position by 1 / 20 to 1 / 4 of the microwave beam width. Microwave link tracking uses off-axis tracking, which can offset the microwave beam center by 1 / 20 to 1 / 4 of the microwave beam width. At this point, the azimuth and elevation voltage errors no longer approach zero, but are superimposed with a smaller voltage offset. Off-axis tracking has a minimal impact on the microwave link's receive level and does not affect microwave link measurement and control communications. It also ensures that the laser link is aligned with the target for measurement and control communications, prioritizing high-speed data transmission over the laser link.

[0039] In summary, the present invention first completes the Ka-band link angle tracking, and then guides the laser link to quickly capture and track, thereby improving the robustness of the laser beam coarse tracking and reducing the capture time; by adopting the microwave link beam off-axis tracking, the simultaneous real-time target tracking of the microwave link and the laser link is realized; after the laser link completes the fine tracking, the laser beam tracking is used for target tracking, which has higher tracking accuracy than the microwave Ka beam tracking; by adopting the microwave link beam off-axis tracking, the problem of the microwave link beam and the laser link beam being unable to be simultaneously aligned with the target due to the inconsistent pointing of the microwave electric axis and the laser optical axis is avoided.

Claims

1. A microwave laser composite antenna off-axis tracking method suitable for deep space exploration, applied to microwave and optical integrated antennas, wherein: The microwave link frequency band is the Ka band, the laser link frequency band is the 1550nm band, and the microwave and laser links share a set of servo tracking equipment; the method is characterized by comprising the following steps: Step 1: The servo tracking device initializes the pointing direction and points the microwave antenna beam toward the satellite target area so that the target is within the coverage of the Ka beam. Step 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 and difference path phase calibration; Step 3: Detect the azimuth voltage error and elevation voltage error of the microwave antenna, transmit the angle error information to the servo tracking device, adjust the microwave antenna pointing direction, adjust the azimuth voltage error and elevation voltage error to be close to 0, so that the target is in the center of the Ka beam, and complete the Ka link angle tracking; Step 4: Use the Ka link tracking result to guide the laser link tracking so that the laser beam covers the satellite target; Step 5: Use the microwave link to guide the laser link to achieve capture and tracking. If there is a mismatch between the microwave link's electrical axis and the laser link's optical axis, causing the target to be unable to be simultaneously centered on both beams, adjust the microwave beam offset by 1 / 20 to 1 / 4 of the beam width to perform off-axis tracking, guiding the laser link beam center toward the target. Step 6: After the laser beam is aligned with the target, the servo tracking device receives the laser link angular error information and tracks the target through the laser link. When the laser beam center is aligned with the target, if the microwave beam center offsets 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.

2. The off-axis tracking method for a microwave laser composite antenna suitable for deep space exploration according to claim 1, characterized in that: The coarse tracking range of the laser link is 350 μrad.

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