Disclosure of Invention
In view of the above, the invention provides a method for tracking the off-axis of a microwave laser composite antenna suitable for deep space exploration. The invention can realize real-time target tracking while a microwave link and a laser link are realized in the microwave and laser integrated measurement and control communication system, and has the characteristics of high tracking precision, high stability and the like.
The purpose of the invention is realized in the following way:
The off-axis tracking method of the microwave laser composite antenna suitable for deep space exploration is applied to a microwave and optical integrated antenna, wherein a microwave link frequency band is a Ka frequency band, a laser link frequency band is a 1550nm frequency band, and the microwave and laser links share a set of servo tracking equipment, and comprises the following steps:
step 1, a servo tracking device initializes pointing, and a microwave antenna beam is pointed to a satellite target area, so that the target is in a Ka beam coverage area;
Step 2, detecting the phase difference between the sum path and the difference path through a Ka link tracking receiver of the microwave antenna, and completing phase correction of the sum path and the difference path;
step 3, detecting azimuth voltage errors and pitching voltage errors of the microwave antenna, transmitting angle error information to servo tracking equipment, adjusting the orientation of the microwave antenna, adjusting the azimuth voltage errors and pitching voltage errors to approach 0, enabling a target to be positioned at the center of a Ka beam, and completing Ka link angle tracking;
Step 4, guiding the laser link to track by adopting a Ka link tracking result, so that the laser beam covers the satellite target;
Step 5, guiding a laser link through a microwave link to achieve capturing and tracking;
And 6, after the laser beam is aligned to the target, the servo tracking equipment receives the laser link angle error information and tracks the target through the laser link.
Further, the coarse tracking range of the laser link is 350 μrad.
In step 5, when the consistency error of the electric axis of the microwave link and the optical axis of the laser link has deviation, and the targets cannot be located at the centers of the two beams at the same time, adjusting the microwave beam offset by 1/20-1/4 of the microwave beam width, performing off-axis tracking, and guiding the beam centers of the laser links to be aligned with the targets.
Further, in step 6, when the laser beam center is aligned to the target, if the microwave beam center offset target position is within the range of 1/20 to 1/4 of the microwave beam width, the microwave link tracking adopts off-axis tracking.
The invention has the following advantages:
1. the invention guides the laser beam to track by using the Ka beam, improves the rough tracking robustness of the laser beam and reduces the capturing time.
2. The invention uses laser beam tracking to track the target, and has higher tracking precision compared with microwave beam tracking.
3. The invention utilizes the off-axis tracking of the microwave beam, and avoids the problem that the microwave beam and the laser beam cannot be aligned to the target at the same time due to inconsistent pointing directions of the microwave electric axis and the laser optical axis.
4. The invention has simple scheme and easy realization, and can be directly applied to the existing microwave and optical integrated antenna.
Detailed Description
The invention will be further described with reference to the accompanying drawings and specific examples.
A method for tracking the off-axis of a microwave laser composite antenna suitable for deep space exploration is applied to a microwave and optical integrated antenna shown in figure 1. The antenna includes a microwave link device and a laser link device. The microwave link equipment comprises a Ka microwave antenna 1, a Ka feed source 2 and a Ka down-converter 3, and the laser link equipment comprises a laser antenna 4, a CCD intensity detector 5 and a laser receiving link 6. The Ka microwave antenna 1 is used for receiving space microwave signals, and the microwave signals are concentrated and transmitted to the Ka feed source 2 through the beam waveguide system. The Ka feed source 2 is used for converting the space microwave signal into two paths of electric signals of a sum path and a difference path, amplifying the electric signals and transmitting the electric signals to the Ka down converter 3. The Ka down converter 3 is configured to down-convert the Ka band signal to an S band signal and then down-convert the signal to a 300M intermediate frequency signal, where the 300M intermediate frequency signal includes a sum path signal and a difference path signal, and transmit the sum path signal and the difference path signal to the tracking receiver 7. The laser antenna 4 receives the spatial laser signal, performs optical path transmission and photoelectric conversion, and transmits the spatial laser signal to the CCD intensity detector 5. The CCD intensity detector 5 is used for detecting the energy of the laser signal, converting the light beam into intensity value data of different pixel positions, and transmitting the intensity value data to the laser receiving link 6. The laser receiving link 6 is used for receiving the laser digital signal, converting the laser digital signal into protocol information which can be identified by the tracking receiver 7, and transmitting the protocol information to the tracking receiver 7. The tracking receiver 7 is used for calculating the microwave link and laser link angle error information. The servo tracking device 8 is used for receiving the angle error information of the tracking receiver 7 and completing the rotation of the antenna to the target.
Taking a D=35 m deep space large-caliber antenna as an example, the Ka frequency band is 26.5 GHz-40 GHz, the calculation is performed according to the frequency of 30GHz, and the calculation formula is calculated according to the half-power beam width of the antennaThe half-power beam width of the obtained 35-meter caliber antenna is 0.02 degrees, and the Ka beam is relatively narrow, so that the capturing of a laser link is guided. The 1550nm wave band of the laser has less background light in deep space and low detected background noise, and has certain advantages in the aspects of high-speed modulation, human eye safety and the like.
The method specifically comprises the following steps:
(1) The antenna servo tracking equipment initializes the pointing direction, and directs the microwave antenna beam to the satellite target area according to satellite orbit data information or other guiding information such as S frequency band, X frequency band pointing, and the like, so that the target is in the Ka beam coverage area.
(2) And detecting the phase difference between the sum path and the difference path by the microwave antenna Ka link tracking receiver, and completing the phase correction of the sum path and the difference path.
(3) The azimuth voltage error and the pitching voltage error of the microwave antenna are detected through a double-channel angle tracking algorithm, angle error information is transmitted to antenna servo tracking equipment, the orientation of the microwave antenna is adjusted, the azimuth voltage error and the pitching voltage error are regulated to approach 0, the target is positioned at the center of a Ka beam, and Ka link angle tracking is completed, and reference is made to FIG. 2.
(4) And guiding the laser link to track by adopting a Ka link tracking result, reducing the coarse tracking search range of the laser link, and enabling the laser beam to cover a satellite target and transfer to the capturing tracking of the laser link after the Ka link angle tracking is completed.
After the Ka microwave link completes angle tracking, the coarse tracking range of the laser link is designed to be 0.02 degree (about 350 mu rad) so as to ensure that the target is covered in the laser beam.
(5) The laser link is guided by the microwave link to achieve capture tracking.
If there is a deviation between the electric axis of the microwave link and the optical axis of the laser link, the target cannot be located at the centers of the two beams at the same time, and in this case, when the microwave beam is aligned to the target, the laser fine tracking cannot be aligned to the target. At this time, the beam width of the microwave beam offset of 1/20-1/4 is adjusted to carry out off-axis tracking, and the beam center of the laser link is guided to be aligned with the target.
(6) After the microwave link guides the laser link to finish capturing and tracking, the center of the laser beam is aligned to the target, and referring to fig. 2, the servo tracking device receives the angle error information of the laser link, and the target tracking is mainly the laser link tracking.
Because the laser link beam is narrower, the tracking precision is higher, and when the laser link finishes fine tracking, the laser link tracking is mainly used, and the laser link controls the servo tracking equipment. When the electric axis of the microwave link and the optical axis of the laser link are consistent, the beam center of the laser link is aligned with the target, and meanwhile, the beam center of the microwave link is also aligned with the target, referring to fig. 2.
Due to the influences of antenna installation errors, gravity, atmospheric refraction and the like, small deviation exists in the directional consistency of the optical axes of the microwave link and the laser link, and when the antennas are pointed at different angles, the directional deviation of the optical axes of the microwave link and the laser link can also slightly change. The beam width of the microwave link deviates from 1/20-1/4 of the beam width of the microwave link basically does not influence the signal receiving of the microwave link, so that the microwave link adopts off-axis tracking to ensure that the beam center of the laser link is aligned with a target, and referring to fig. 3, the axis 1 represents the beam center position of the microwave link, and the axis 2 represents the beam center position of the laser link.
After the laser link completes self-tracking, the microwave link keeps off-axis tracking to track the target.
In the invention, when the laser beam center is aligned with a target, the microwave beam center is deviated from the target position within the range of 1/20-1/4 microwave beam width, the microwave link tracking adopts off-axis tracking, and the microwave beam width of the microwave beam center can be deviated by 1/20-1/4, so that the azimuth voltage error and the pitching voltage error are not approximate to 0 any more, and the smaller voltage offset is superimposed. The off-axis tracking has small influence on the receiving level of the microwave link, does not influence the measurement and control communication of the microwave link, can ensure that the laser link performs measurement and control communication aiming at a target, and preferentially ensures that the laser link performs high-rate data transmission.
In a word, the method and the device for tracking the target by using the microwave link have the advantages that Ka frequency band link angle tracking is finished, laser link fast capture tracking is guided, coarse tracking robustness of laser beams is improved, capture time is shortened, microwave link beam off-axis tracking is adopted, simultaneous real-time target tracking of microwave links and laser link double chains is achieved, after fine tracking is finished by the laser link, target tracking is conducted by means of laser beam tracking, compared with microwave Ka beam tracking, tracking accuracy is higher, and the problem that microwave link beams and laser link beams cannot be aligned to targets simultaneously due to inconsistent directions of microwave electric axes and laser optical axes is avoided by means of microwave link beam off-axis tracking.