Space Terahertz Communication Beam Tracking Device and Method Based on Beam Waveguide

Abstract

This invention discloses a space terahertz communication beam tracking device and method based on beamguides. The device includes: a terahertz beamguide tracking antenna, a dual-channel terahertz receiver, an angle tracking receiver, a tracking controller, a position and attitude sensor, and a two-dimensional servo rotation mechanism. The dual-channel terahertz receiver processes the terahertz sum and difference signals to obtain intermediate frequency (IF) sum and difference signals. The angle tracking receiver obtains an error angle signal based on the IF sum and difference signals. The position and attitude sensor measures the position and attitude values ​​in real time. The tracking controller obtains a compensation error angle based on the error angle signal and the position and attitude values, and controls the rotation of the two-dimensional servo rotation mechanism based on the compensation error angle. This invention solves the problems of traditional methods where the RF receiver needs to be rigidly linked to the terahertz antenna via a waveguide and rotate with the antenna, thus increasing the rotational inertia of the servo rotation mechanism and requiring the additional use of a microwave rotary joint.

Description

Technical Field

[0001] This invention belongs to the field of terahertz technology, and particularly relates to a spatial terahertz communication beam tracking device and method based on beam waveguide. Background Technology

[0002] The terahertz band possesses abundant spectrum resources, making it highly suitable for broadband high-speed communication applications. Currently, with the gradual depletion of low-frequency microwave spectrum resources, mobile communication frequencies are increasing, and satellite communication frequencies have reached the Q / V band, with a trend towards even higher frequencies. However, the beamwidth of a terahertz antenna is directly proportional to its operating frequency; for antennas of the same physical aperture, the higher the operating frequency, the narrower the beamwidth. Due to current technological limitations, the transmission power of terahertz signal sources is relatively low. Long-distance terahertz communication typically requires large-aperture antennas to compensate for free-space losses, resulting in extremely narrow antenna beamwidths. Under narrow beam conditions, if the beam alignment accuracy at the transmitting and receiving ends is not high, it will cause significant pointing loss, rendering normal communication impossible. Furthermore, except for fixed-point terrestrial communication, most scenarios involve communication nodes maintaining relative motion. During communication, the antenna of one node needs to be dynamically aligned with the target node simultaneously, requiring dynamic tracking of the antenna beam while maintaining high tracking accuracy. The reported terahertz beam tracking primarily utilizes either monopulse mechanical scanning or phased array electrical scanning. However, phased array electrical scanning is limited by technological limitations, restricting the array size and hindering long-distance applications. Furthermore, the antenna cannot directly achieve 360° azimuth tracking. Traditional monopulse mechanical scanning is constrained by the lack of a 360° azimuth rotation joint for the terahertz band. Additionally, the terahertz receiver requires a rigid waveguide connection to the monopulse antenna feed, necessitating simultaneous rotation with the antenna during tracking. This increases the rotational inertia of the servo rotation mechanism, requiring external installation for space applications and introducing additional temperature control issues. If signal processing equipment such as angle tracking receivers is mounted on the stator of the servo rotation mechanism, an additional microwave rotation joint is needed to achieve 360° azimuth rotation; otherwise, mounting it on the rotor would further increase the rotational inertia of the servo rotation mechanism. Summary of the Invention

[0003] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a space terahertz communication beam tracking device and method based on beam waveguide. This solves the problems in traditional terahertz monopulse tracking systems where the radio frequency receiver needs to be hard-linked to the terahertz antenna through a waveguide and rotate with the antenna, thus increasing the rotational inertia of the servo rotation mechanism, and where an additional microwave rotary joint is required.

[0004] The objective of this invention is achieved through the following technical solution: a space terahertz communication beam tracking device based on beamguides, comprising: a terahertz beamguide tracking antenna, a terahertz dual-channel receiver, an angle tracking receiver, a tracking controller, a position and attitude sensor, and a two-dimensional servo rotation mechanism; wherein, the terahertz beamguide tracking antenna is connected to the two-dimensional servo rotation mechanism; the terahertz beamguide tracking antenna: receives the terahertz signal transmitted by the target, obtains the terahertz sum signal and the terahertz difference signal based on the terahertz signal, and transmits the terahertz sum signal and the terahertz difference signal to the terahertz dual-channel receiver; the terahertz dual-channel receiver: receives the terahertz sum signal and the terahertz difference signal, and transmits... The terahertz sum signal and terahertz difference signal are down-converted to intermediate frequency (IF) to obtain an IF sum signal and an IF difference signal, respectively. These signals are then transmitted to the angle tracking receiver. The angle tracking receiver receives the IF sum signal and IF difference signal, obtains an error angle signal based on them, and transmits the error angle signal to the tracking controller. The position and attitude sensor measures the position and attitude values ​​in real time and transmits these values ​​to the tracking controller. The tracking controller receives the error angle signal and the position and attitude values, obtains a compensation error angle based on these values, and controls the rotation of the two-dimensional servo rotation mechanism based on the compensation error angle to achieve target tracking.

[0005] In the aforementioned space terahertz communication beam tracking device based on beam waveguides, the terahertz beam waveguide tracking antenna includes a main reflector, a sub-reflector, a beam waveguide quasi-optical front end, and a single-pulse feed source; wherein, the terahertz signal emitted by the target is sequentially fed into the single-pulse feed source through the main reflector, the sub-reflector, and the beam waveguide quasi-optical front end; the single-pulse feed source obtains the terahertz sum signal and the terahertz difference signal based on the terahertz signal.

[0006] In the aforementioned space terahertz communication beam tracking device based on beam waveguide, the beam waveguide quasi-optical front end includes a first frequency-selective surface reflector, a first ellipsoidal reflector, a second ellipsoidal reflector, a second frequency-selective surface reflector, a first terahertz absorbing material, and a second terahertz absorbing material; wherein, the first terahertz absorbing material is disposed at the rear of the first frequency-selective surface reflector; the second terahertz absorbing material is disposed at the rear of the second frequency-selective surface reflector; the terahertz signal reflected by the sub-reflector is reflected by the first frequency-selective surface reflector to the first ellipsoidal reflector, then reflected by the first ellipsoidal reflector to the second ellipsoidal reflector, then reflected by the second ellipsoidal reflector to the second frequency-selective surface reflector, and finally reflected by the second frequency-selective surface reflector and fed into the single-pulse feed source.

[0007] In the aforementioned space terahertz communication beam tracking device based on beam waveguide, the main reflector, the sub-reflector, and the first frequency-selective surface reflector are disposed at the pitch axis rotor end of the two-dimensional servo rotation mechanism; the pitch axis, the first ellipsoidal reflector, the second ellipsoidal reflector, and the second frequency-selective surface reflector of the two-dimensional servo rotation mechanism are disposed at the azimuth axis rotor end of the two-dimensional servo rotation mechanism; and the electrical axis of the single-pulse feed source is coaxial with the azimuth axis of the two-dimensional servo rotation mechanism.

[0008] In the aforementioned space terahertz communication beam tracking device based on beam waveguides, the error angle signal includes the target-antenna electrical axis crossing elevation error angle and the elevation error angle signal U. ΔXEL and U ΔEL .

[0009] In the aforementioned space terahertz communication beam tracking device based on beam waveguides, the signals of the target-antenna electrical axis crossing elevation error angle and the elevation error angle are obtained through the following formulas:

[0010]

[0011] Among them, U ΔXEL U is the signal of the pitch error angle between the target and the antenna electrical axis. ΔEL The signal is the pitch error angle between the target and the antenna electrical axis, μ. xel μ is the normalized difference slope constant in the cross-pitch direction. el Let θ be the normalized difference slope constant in the pitch direction. F The off-axis error angle of the target deviation from the electric axis of the single-pulse feed source; This represents the off-axis error angle phase.

[0012] In the aforementioned space terahertz communication beam tracking device based on beam waveguides, the target-antenna electrical axis crossing elevation error angle and elevation error angle are obtained by the following formulas:

[0013]

[0014] Where ΔXEL is the target-antenna electrical axis crossing elevation error angle, ΔEL is the target-antenna electrical axis crossing elevation error angle, Φ is the phase difference caused by the real-time azimuth and elevation positions of the terahertz beam waveguide tracking antenna, and U ΔXEL U is the signal of the pitch error angle between the target and the antenna electrical axis. ΔEL The signal is the pitch error angle between the target and the antenna electrical axis, μ. xel μ is the normalized difference slope constant in the cross-pitch direction. el is the normalized difference slope constant in the pitch direction.

[0015] In the aforementioned space terahertz communication beam tracking device based on beam waveguides, the compensation error angle is obtained using the following formula:

[0016]

[0017] Where, δ az δ represents the error angle that needs to be compensated for on the orientation axis of the two-dimensional servo rotation mechanism. el Let be the pitch angle that needs to be compensated for in the two-dimensional servo rotation mechanism, e be the angle between the azimuth plane of the two-dimensional servo rotation mechanism and the pitch plane of the terahertz beam waveguide tracking antenna, ΔXEL be the pitch error angle of the target and antenna electrical axis intersection, and ΔEL be the pitch error angle of the target and antenna electrical axis intersection.

[0018] A method for beam tracking in space terahertz communication based on beam waveguides, using a beam waveguide-based space terahertz communication beam tracking device, includes:

[0019] Step S100: Calibrate the space terahertz communication beam tracking device based on beam waveguide;

[0020] Step S200: The calibrated beamguide-based spatial terahertz communication beam tracking device coarsely points to the target;

[0021] Step S300: After the coarse pointing is completed, if the angle tracking receiver reports that the target has not been acquired, the calibrated space terahertz communication beam tracking device based on beam waveguide updates the coarse pointing angle of the terahertz beam waveguide tracking antenna. The dynamic spiral scanning search is performed with the half beam width of the terahertz beam waveguide tracking antenna as the step size until the angle tracking receiver reports that the target has been acquired.

[0022] Step S400: The calibrated space terahertz communication beam tracking device based on beam waveguide is used by the tracking controller to calculate the error angle in real time according to the error angle signal output by the angle tracking receiver, and controls the two-dimensional servo rotation mechanism to compensate for the error angle, so that the terahertz beam waveguide tracking antenna can point to the target in real time to achieve dynamic tracking.

[0023] Step S500: If the dynamically tracked target is lost, return to step S200.

[0024] In the above-mentioned spatial terahertz communication beam tracking method based on beam waveguide, in step S300, if the target is not captured after a preset number of spiral line scanning searches, a noise reduction search is performed until the target is captured.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] (1) By adding a beam waveguide in the radio frequency optical path, the present invention can fix the terahertz radio frequency receiver to the stator end of the servo rotation mechanism of the device, reduce the load torque of the servo rotation structure, improve the dynamic performance of the device when using a motor with the same torque, or use a motor with a lower torque when achieving the same dynamic performance, thereby reducing the size and power consumption of the device.

[0027] (2) The present invention can improve the reliability of the device and reduce the cost by replacing the use of the rotating joint with beam space rotation under the premise of satisfying 360° azimuth tracking;

[0028] (3) The present invention can install all other modules except the main and sub-reflectors and the beam waveguide inside the space satellite cabin, which is conducive to the miniaturization of the system and the constant temperature, and improves the stability of the system;

[0029] (4) This invention proposes a quasi-optical front-end with a 4-mirror beam waveguide tracking structure using a frequency-selective surface mirror structure. The number of mirrors is reduced by 1 / 3 compared to the traditional 6-mirror structure, resulting in a significant reduction in device size. The use of frequency-selective surface mirrors in the beam waveguide can suppress out-of-band terahertz signals and reduce received signal noise. The quasi-optical front-end in this embodiment can not only perform normal optical path changes, but also improve the system signal-to-noise ratio.

[0030] (5) The terahertz band monopulse feed proposed in this invention uses circularly polarized orthogonal dual-mode to achieve common optical path transmission of sum-mode / differential-mode dual-channel signals, which can significantly reduce the volume occupied by the feed. One preferred solution is to use a terahertz multimode circularly polarized monopulse feed composed of a circular polarizer, a sum-difference converter and a multimode horn cascaded together, which effectively improves the overall efficiency of the terahertz tracking antenna compared with the traditional multi-horn monopulse feed.

[0031] (6) This invention proposes a new beam tracking method, which improves the anti-noise and anti-interference capabilities of communication beam tracking by using noise reduction search and capture technology; and the noise reduction algorithms are all implemented by software programming, which has the advantages of quick implementation and low cost. Attached Figure Description

[0032] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0033] Figure 1 This is a structural block diagram of a space terahertz communication beam tracking device based on beam waveguide provided in an embodiment of the present invention;

[0034] Figure 2This is a schematic diagram of the terahertz beam waveguide tracking antenna provided in an embodiment of the present invention;

[0035] Figure 3 These are schematic diagrams of three different coordinate systems involved in the tracking device provided in the embodiments of the present invention;

[0036] Figure 4 This is a flowchart of the tracking method of the tracking device provided in the embodiment of the present invention. Detailed Implementation

[0037] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0038] Figure 1 This is a structural block diagram of a space terahertz communication beam tracking device based on a beam waveguide, provided in an embodiment of the present invention. Figure 1 As shown, the space terahertz communication beam tracking device based on beam waveguide includes: a terahertz beam waveguide tracking antenna 1, a terahertz dual-channel receiver 2, an angle tracking receiver 3, a tracking controller 4, a position and attitude sensor 5, and a two-dimensional servo rotation mechanism 6; wherein,

[0039] The terahertz beam waveguide tracking antenna 1 is connected to the two-dimensional servo rotation mechanism 6;

[0040] Terahertz beam waveguide tracking antenna 1: Receives the terahertz signal emitted by the target, and obtains the terahertz frequency and signal μ from the terahertz signal. Σ (t) and the terahertz difference signal μ Δ (t), the terahertz sum signal and the terahertz difference signal are transmitted to the terahertz dual-channel receiver 2;

[0041] Terahertz dual-channel receiver 2: Receives the terahertz sum signal and the terahertz difference signal, and down-converts the terahertz sum signal and the terahertz difference signal to intermediate frequency (IF) respectively to obtain the IF sum signal μ. ΣIF (t) and the intermediate frequency difference signal μ ΔIF (t), which combines the intermediate frequency and signal μ ΣIF (t) and the intermediate frequency difference signal μ ΔIF (t) Transmitted to angle tracking receiver 3;

[0042] Angle tracking receiver 3: Receives the intermediate frequency sum signal and intermediate frequency difference signal, obtains the error angle signal based on the intermediate frequency sum signal and intermediate frequency difference signal, and transmits the error angle signal to the tracking controller 4; wherein, the error angle signal includes the target-antenna electrical axis crossing pitch error angle and pitch error angle signal U. ΔXEL and U ΔEL ;

[0043] Position and attitude sensor 5: measures position and attitude values ​​in real time and transmits the position and attitude values ​​to tracking controller 4;

[0044] Tracking controller 4: Receives error angle signal and position attitude value, obtains compensation error angle based on error angle signal and position attitude value, controls two-dimensional servo rotation mechanism 6 to rotate based on compensation error angle to compensate for the error angle of terahertz beam waveguide tracking antenna 1 pointing to the target, and realizes target tracking.

[0045] The device receives terahertz wave signals emitted by the cooperative target, measures and evaluates the two-dimensional error angle between the target's terahertz wave signal and the antenna's electrical axis, and controls the high-precision two-dimensional servo rotation mechanism 6 to rotate to compensate for the error angle in real time, thereby realizing the dynamic tracking of the target by the terahertz beam waveguide tracking antenna 1.

[0046] In the tracking device, the terahertz beam waveguide tracking antenna 1 is used to receive terahertz signals and generate terahertz signals μ for measuring the two-dimensional angle of the target. Σ (t) and difference signal μ Δ (t); Terahertz dual-channel receiver 2 is used to down-convert two terahertz signals to intermediate frequency (IF), generating IF and signal μ. ΣIF (t) and the intermediate frequency difference signal μ ΔIF (t); Angle tracking receiver 3 is responsible for acquiring and processing the intermediate frequency signal and difference signal, and obtaining the target-antenna electrical axis crossing elevation error angle ΔXEL and elevation error angle ΔEL signals U respectively. ΔXEL and U ΔEL The position and attitude sensor 5 is used to measure the state information of the six degrees of freedom of the tracking device in real time: longitude, latitude, altitude, heading angle, pitch angle and roll angle; the high-precision two-dimensional servo rotation mechanism 6 is equipped with a terahertz beam waveguide tracking antenna 1 to realize the pointing of the antenna beam to any target; the tracking controller 4 is responsible for controlling the high-precision two-dimensional servo rotation mechanism 6 through the tracking algorithm and combined with the two-dimensional error angle signal and position and attitude signal measured in real time by the position and attitude sensor 5 to realize the acquisition and tracking of terahertz targets.

[0047] Figure 2 This is a schematic diagram of the principle of the terahertz beam waveguide tracking antenna 1 provided in an embodiment of the present invention. Figure 2As shown, the terahertz beam waveguide tracking antenna 1 includes a main reflector 11, a sub-reflector 12, a beam waveguide quasi-optical front end, and a single-pulse feed 17; wherein, the terahertz signal emitted by the target is sequentially fed into the single-pulse feed 17 through the main reflector 11, the sub-reflector 12, and the beam waveguide quasi-optical front end; the single-pulse feed 17 obtains the terahertz sum signal and the terahertz difference signal based on the terahertz signal.

[0048] The single-pulse feed 17 employs circularly polarized orthogonal dual-mode to achieve common optical path transmission of sum-mode / differential-mode dual-channel signals. Preferably, the sum-mode signal is implemented using TE11 mode, and the differential-mode signal is implemented using TE21 mode.

[0049] The beamguide collimating optical front end includes a first frequency-selective surface reflector 13, a first ellipsoidal reflector 14, a second ellipsoidal reflector 15, a second frequency-selective surface reflector 16, a first terahertz absorbing material 18, and a second terahertz absorbing material 19. The first terahertz absorbing material 18 is disposed at the rear of the first frequency-selective surface reflector 13, and the second terahertz absorbing material 19 is disposed at the rear of the second frequency-selective surface reflector 16. The terahertz signal reflected by the sub-reflector 12 is reflected by the first frequency-selective surface reflector 13 and then reaches the first ellipsoidal reflector 14, then is reflected by the first ellipsoidal reflector 14 and then reaches the second ellipsoidal reflector 15, then is reflected by the second ellipsoidal reflector 15 and then reaches the second frequency-selective surface reflector 16, and finally is reflected by the second frequency-selective surface reflector 16 and fed into the single-pulse feed source 17.

[0050] The main reflector 11, the secondary reflector 12, and the first frequency-selective surface reflector 13 are disposed at the pitch axis rotor end of the two-dimensional servo rotation mechanism 6; the pitch axis, the first ellipsoidal reflector 14, the second ellipsoidal reflector 15, and the second frequency-selective surface reflector 16 of the two-dimensional servo rotation mechanism 6 are disposed at the azimuth axis rotor end of the two-dimensional servo rotation mechanism 6; the electric axis of the single-pulse feed source 17 is coaxial with the azimuth axis of the two-dimensional servo rotation mechanism 6.

[0051] For a shaft system consisting of a motor, a rotating shaft, and bearings (which can be a pitch axis or an azimuth axis), there are stator ends and rotor ends. When the rotating shaft is driven to rotate by the motor, the stator ends remain stationary while the rotor ends rotate.

[0052] The electromagnetic wave transmission path formed by the beamguide quasi-optical front end is a vertical Ω structure. That is, the terahertz electromagnetic wave signal is input vertically downward into the beamguide quasi-optical front end, reflected by the frequency-selective surface reflector 13 and horizontally illuminated by the ellipsoidal reflector 14, reflected by the ellipsoidal reflector 14 and vertically downward to the ellipsoidal reflector 15, reflected by the ellipsoidal reflector 15 and horizontally to the frequency-selective surface reflector 16, and reflected by the frequency-selective surface reflector 16 and vertically downward to be output from the beamguide quasi-optical front end.

[0053] The terahertz beam waveguide tracking antenna 1 receives the terahertz plane wave signal emitted by the target via the following transmission path: main reflector 11, sub-reflector 12, frequency-selective surface reflector 13, ellipsoidal mirror 14, ellipsoidal mirror 15, frequency-selective surface reflector 16, and finally fed into the single-pulse feed source 17 at the focal point. The main reflector 11, sub-reflector 12, and frequency-selective surface reflector 13 are mounted on the pitch axis rotor end of the high-precision two-dimensional servo rotation mechanism 6, forming the pitch axis system of the rotation mechanism, which is driven by the pitch axis motor to rotate together around the pitch axis. The pitch axis system, ellipsoidal mirror 14, ellipsoidal mirror 15, and frequency-selective surface reflector 16 are mounted on the azimuth axis rotor end of the high-precision two-dimensional servo rotation mechanism 6, forming the azimuth axis system of the rotation mechanism, which is driven by the azimuth axis motor to rotate together around the azimuth axis. The single-pulse feed source 17 is mounted on the azimuth axis stator end of the high-precision two-dimensional servo rotation mechanism 6, and does not rotate with the pitch or azimuth axis of the rotation mechanism, remaining stationary relative to the mounting platform of the tracking device. When the pointing of the terahertz beam waveguide tracking antenna 1 rotates along the azimuth and elevation axes of the high-precision two-dimensional servo rotation mechanism 6, the terahertz beam will rotate within the beam waveguide quasi-optical front end 20. That is, the terahertz beam rotates as it enters the single-pulse feed 17, following the azimuth and elevation axis rotation of the high-precision two-dimensional servo rotation mechanism 6. Since the single-pulse feed 17 itself remains stationary, the positions of the terahertz dual-channel receiver 2 and the angle tracking receiver 3 connected after the feed are fixed, avoiding the use of terahertz and microwave rotation joints. The single-pulse feed 17 ultimately outputs terahertz signals and μ. Σ (t) and difference signal μ Δ (t), the signal is input to the terahertz dual-channel receiver 2 through the terahertz waveguide.

[0054] The terahertz dual-channel receiver 2 will convert two terahertz signals μ Σ (t) and μ Δ (t) Down-convert to intermediate frequency, angle tracking receiver 3 pairs of two intermediate frequency signals μ ΣIF (t) and μ ΔIF (t) is collected and processed in the digital domain to finally obtain the digital error angle voltage signals U in the cross-pitch and pitch directions. ΔXEL and U ΔEL And output it to the tracking controller 4.

[0055] Figure 3 These are schematic diagrams illustrating three different coordinate systems involved in the tracking device of this invention. For example... Figure 3 As shown, unlike traditional tracking devices, this device involves three coordinate systems: the antenna error angular coordinate system (XEL-EL coordinate system, describing the two-dimensional error angle of the target relative to the electrical axis of the main reflector 11 of the terahertz beam waveguide tracking antenna 1), the feed error angular coordinate system (XEL... F -EL FThe coordinate system (a two-dimensional error angle describing the target relative to the electrical axis of the monopulse feed 17 of the terahertz beam waveguide tracking antenna 1) and the servo rotation mechanism coordinate system (AZ-EL coordinate system, a two-dimensional coordinate system describing the two-dimensional servo rotation mechanism 6) are not coincident, wherein the direct measurement of the error angle signal occurs in the XEL coordinate system. F -EL F The evaluation of the true value of the error angle occurs in the XEL-EL coordinate system, while the compensation for the error angle occurs in the AZ-EL coordinate system.

[0056] The error angular voltage signal output by the angle tracking receiver 3 can be expressed as:

[0057]

[0058] In equation 1) above, μ xel and μ el θ represents the normalized difference slope constants in the cross-pitch and pitch directions, respectively, corresponding to the angular sensitivity of the tracking device in the azimuth and pitch directions; F The off-axis error angle of the target deviation from the electric axis of the single-pulse feed source 17; The value representing the direction of the target's deviation from the electrical axis of the single-pulse feed 17 is defined as the off-axis error angle phase, which determines the off-axis error angle θ. F The components ΔXEL of the cross pitch and pitch directions in the feed error angular coordinate system. F and ΔEL F .

[0059] Since the two-dimensional error angles ΔXEL and ΔEL of the target deviating from the electrical axis of the terahertz beamguide tracking antenna 1 are fed into the single-pulse feed source 17 via reflection from the beamguide, they will rotate with the azimuth and pitch motion of the terahertz beamguide tracking antenna 1. The magnitude of the off-axis error angle θ remains unchanged, i.e., θ = θ F What changes is the off-axis error angle phase. Right now Assuming the phase component caused by the real-time azimuth a and elevation e of the terahertz beam waveguide tracking antenna 1 is Φ1, and the fixed phase component caused by other factors is Φ2, then Equation 1) can be expressed as:

[0060]

[0061] Before tracking a target, the tracking device needs to calibrate the phase and the normalized difference slope in both directions. The calibration process is as follows: Place a terahertz beacon source at any fixed point P0(a0, e0), align the terahertz beamguide tracking antenna 1 with the direction of maximum received signal strength after aligning it with the target, then move the antenna to a small negative offset angle in the cross-tilt direction, adjusting the phase difference between the diagonal tracking receiver 3 and the channel and difference channel signals, adding an additional phase difference. This causes the corresponding angle tracking receiver 3 to output U ΔEL0 =0, which is consistent with the actual situation where the terahertz beam waveguide tracking antenna 1 deviates from the target. After phase calibration, the normalized difference slope μ in the cross-pitch and pitch directions is further adjusted at P0. xel and μ el Calibration is performed. The calibration process is as follows: After aligning the terahertz beam waveguide tracking antenna 1 with the beacon source, it is deflected by a very small angle in the cross-elevation direction. At the same time, the orientation deviation angle below the XEL-EL coordinate system of the rotating mechanism and the corresponding cross-elevation error angle signal output by the angular tracking receiver 3 are recorded. The data are then linearly fitted to obtain the normalized difference slope μ in the cross-elevation direction. xel Similarly, after aligning the terahertz beam waveguide tracking antenna 1 with the beacon source, the normalized difference slope μ in the elevation direction can be calibrated. el By following the steps above, the phase calibration and normalized difference slope calibration of this device are completed.

[0062] When the target is tracked to point P(a, e), the azimuth angle of the terahertz beamguide tracking antenna 1 changes from a0 to a, and the elevation angle changes from e0 to e. At this time, the phase difference caused by the azimuth and elevation positions of the terahertz beamguide tracking antenna 1 is Φ. Then:

[0063]

[0064] Equation 3) can be further transformed into matrix form:

[0065]

[0066] In Equation 4) above, the target's deviation from the terahertz beam waveguide tracking antenna's electrical axis cross-pitch and pitch error angles ΔXEL and ΔEL in the antenna error angular coordinate system can be obtained through the azimuth error angle signal U output by the current angle tracking receiver 3. ΔXEL Pitch error angle signal U ΔEL Normalized difference slope calibration value μ xel and μ el The phase value Φ is calculated from the equation.

[0067] During the cross-pitch rotation of the terahertz beam waveguide tracking antenna 1 along the azimuth axis of the high-precision two-dimensional servo rotation mechanism 6, the first frequency-selective surface reflector 13, the first ellipsoidal reflector 14, the second ellipsoidal reflector 15, and the second frequency-selective surface reflector 16 all rotate simultaneously with the antenna's main reflector 11 and sub-reflector 12 at the same angle. The beam illuminating the single-pulse feed source 17 is equivalent to the beam illuminating directly without passing through the beam waveguide. The phase change of the error angular vector caused by the movement of the azimuth axis of the high-precision two-dimensional servo rotation mechanism 6 from a0 to a is always Φ. a=a-a0. During the elevation rotation of the terahertz beamguide tracking antenna 1 along the elevation axis of the high-precision two-dimensional servo rotation mechanism 6, the beamguide reflector 13 rotates simultaneously with the antenna's main reflector 11 and sub-reflector 12 by the same angle. The first ellipsoidal reflector 14, the second ellipsoidal reflector 15, the second frequency-selective surface reflector 16, and the monopulse feed 17 do not move with the elevation axis. The phase change of the error angular vector caused by the high-precision two-dimensional servo rotation mechanism 6 moving from e0 to e is always Φ. e =e0-e. In Equation 4), the phase Φ is the change in the error angular vector caused by the rotation of the azimuth and pitch axes of the high-precision two-dimensional servo rotation mechanism. Φ = Φ a +Φ e =a-a0+e0=(ae)-(a0-e0).

[0068] In the tracking device, there is an angle 'e' between the azimuth plane of the high-precision two-dimensional servo rotation mechanism 6 and the elevation plane of the terahertz beam waveguide tracking antenna 1. The elevation plane of the high-precision two-dimensional servo rotation mechanism 6 coincides with the elevation plane of the terahertz beam waveguide tracking antenna 1. Therefore, for the error angles ΔXEL and ΔEL in the antenna error angular coordinate system, the high-precision two-dimensional servo rotation mechanism 6 needs to compensate for the error angle δ. az and δ el The relationship between the two is as follows:

[0069]

[0070] Using equations 4) and 5), the relationship between the error angle that the high-precision two-dimensional servo rotation mechanism 6 needs to compensate in real time during the tracking process of the terahertz beam waveguide tracking antenna 1 and other known quantities can be obtained as follows:

[0071]

[0072] The tracking device in this embodiment solves the problem of large load torque in the servo rotating mechanism of traditional space terahertz communication beam tracking systems, which is detrimental to miniaturization, by using a terahertz beam waveguide tracking antenna. It also avoids the use of multiple microwave rotating joints, improving system reliability. Furthermore, the quasi-optical front end of the tracking device proposed in this embodiment employs a frequency-selective surface planar mirror, simultaneously achieving beam reflection of useful in-band signals and attenuation and absorption of out-of-band spurious and noise signals. The single-pulse feed uses a circularly polarized orthogonal dual-mode approach to achieve common optical path transmission of both normal-mode and differential-mode signals, reducing the feed size.

[0073] like Figure 4 As shown, this embodiment also provides a spatial terahertz communication beam tracking method based on beam waveguides, the method comprising:

[0074] Step S100: Calibrate the space terahertz communication beam tracking device based on beam waveguide;

[0075] Step S200: The calibrated beamguide-based spatial terahertz communication beam tracking device coarsely points to the target;

[0076] Step S300: After the coarse pointing is completed, if the angle tracking receiver 3 reports that the target has not been acquired, the calibrated space terahertz communication beam tracking device based on beam waveguide updates the coarse pointing angle of the terahertz beam waveguide tracking antenna 1, and performs dynamic spiral scanning search with the half beam width of the terahertz beam waveguide tracking antenna 1 as the step, until the angle tracking receiver 3 reports that the target has been acquired.

[0077] Step S400: The calibrated space terahertz communication beam tracking device based on beam waveguide is calculated in real time by the tracking controller 4 according to the error angle signal output by the angle tracking receiver 3, and the two-dimensional servo rotation mechanism 6 is controlled to compensate for the error angle, so that the terahertz beam waveguide tracking antenna 1 can be pointed at the target in real time to achieve dynamic tracking.

[0078] Step S500: If the dynamically tracked target is lost, return to step S200.

[0079] The tracking process consists of six main steps, described in detail below:

[0080] Step 1: Calibration. Perform phase calibration and normalized difference slope calibration of this device using a beacon source at any fixed point P0.

[0081] Step Two: Coarse Pointing. Based on the target's real-time position obtained from known target ephemeris or other means, and the real-time attitude and position information of the device measured by the position and attitude sensor 5, the tracking device calculates the two-dimensional pointing angle of the terahertz beam waveguide tracking antenna 1 towards the target in the coordinate system of the high-precision two-dimensional servo rotation mechanism 6, including a certain error. It then controls the rotation of the azimuth and elevation axes of the high-precision two-dimensional servo rotation mechanism 6 to point the terahertz beam waveguide tracking antenna 1 towards the vicinity of the target position. This error is due to the deviation in the real-time target position obtained by the tracking device and the measurement error of the position and attitude sensor 5.

[0082] Step 3: Search and Acquisition. After coarse pointing is completed, if the angle tracking receiver 3 reports that the target has not been acquired, the tracking controller 4 will update the coarse pointing angle of the terahertz beam waveguide tracking antenna 1 in real time according to Step 2, and add a spiral scanning angle component with a step size of half the beamwidth of the terahertz beam waveguide tracking antenna 1 on this basis to realize dynamic spiral scanning search until the angle tracking receiver 3 reports that the target has been acquired.

[0083] Step 4: Noise Reduction Search and Acquisition. If the target is not acquired after a preset number of spiral scan searches, a noise reduction search and acquisition process is initiated. Depending on the target satellite's transmission standard, two noise reduction methods can be selected: one method is to reduce the intermediate frequency bandwidth of the dual-channel receiver to 1 / 10 of the previous intermediate frequency bandwidth; the other method is to perform digital phase-locked filtering according to the modulation frequency convention. After completing the above noise reduction steps, a spiral scan search is performed again until the target is acquired.

[0084] Step 5: Dynamic Tracking. If the angle tracking receiver 3 reports that the target has been acquired, the dynamic tracking process begins. At this time, the tracking device calculates the two-dimensional error angle, i.e., the compensation error angle, in real time based on the cross-pitch and pitch error signals output by the angle tracking receiver 3, and controls the high-precision two-dimensional servo rotation mechanism 6 to perform two-dimensional error angle compensation, ensuring that the Hertz beam waveguide tracking antenna 1 points to the target in real time to achieve target tracking.

[0085] Step Six: Target Loss. If the target is lost for any reason, and the angle tracking receiver 3 reports that the target has not been acquired, the process will re-enter the coarse pointing procedure in Step Two.

[0086] The two-dimensional error angle calculation involves three different coordinate systems. The target error angle is measured in the feed error angle coordinate system; that is, the device directly measures the error angle of the target's deviation from the feed, called the feed error angle. The error angle is evaluated in the antenna error angle coordinate system; that is, the device needs to confirm and evaluate the error angle of the target's deviation from the antenna, called the antenna error angle. The error angle compensation occurs in the azimuth and elevation coordinate system of the rotating mechanism; that is, the device needs to compensate for the antenna error angle in the azimuth and elevation coordinate system of the rotating mechanism, called the rotating mechanism compensation angle. The two-dimensional error angle calculation is based on the two signals corresponding to the feed error angle output by the angle tracking receiver 3, mapped to the rotating mechanism compensation angle through calibration parameters and coordinate system transformation.

[0087] The feed error angle includes the feed elevation error angle and the cross elevation error angle; the antenna error angle includes the antenna elevation error angle and the cross elevation error angle; and the rotation mechanism compensation angle includes the rotation mechanism azimuth compensation angle and the elevation compensation angle.

[0088] This embodiment, by adding a beam waveguide to the radio frequency optical path, allows the terahertz radio frequency receiver to be fixed to the stator end of the device's servo rotation mechanism, reducing the load torque of the servo rotation structure. This improves the device's dynamic performance when using a motor with the same torque, or allows the use of a lower torque motor to achieve the same dynamic performance, thereby reducing the device's size and power consumption. This embodiment can replace the use of a rotary joint with beam spatial rotation while meeting 360° azimuth tracking requirements, improving device reliability and reducing costs. This invention allows all modules except the main and sub-reflectors and the beam waveguide to be installed inside the space satellite cabin, facilitating system miniaturization and temperature stability, thus improving system stability. This invention proposes a 4-mirror beam waveguide tracking quasi-optical front-end with a frequency-selective surface mirror structure, reducing the number of mirrors by 1 / 3 compared to the traditional 6-mirror design, significantly reducing the device's size. The use of frequency-selective surface mirrors in the beam waveguide can suppress out-of-band terahertz signals and reduce received signal noise. The novel quasi-optical front end proposed in this embodiment can not only perform normal optical path changes, but also improve the system signal-to-noise ratio. The terahertz band monopulse feed proposed in this invention uses circularly polarized orthogonal dual modes to achieve common optical path transmission of sum-mode / differential-mode dual-channel signals, which can significantly reduce the volume occupied by the feed. One preferred solution is to use a terahertz multimode circularly polarized monopulse feed composed of a circular polarizer, a sum-difference converter, and a multimode horn cascaded together, which effectively improves the overall efficiency of the terahertz tracking antenna compared to the traditional multi-horn monopulse feed. This embodiment proposes a new beam tracking method, which uses noise reduction search and acquisition technology to improve the noise and interference resistance of communication beam tracking. Moreover, the noise reduction algorithms are all implemented by software programming, which has the advantages of fast implementation and low cost.

[0089] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A space terahertz communication beam tracking device based on beam waveguide, characterized in that... include: The system comprises a terahertz beam waveguide tracking antenna (1), a terahertz dual-channel receiver (2), an angle tracking receiver (3), a tracking controller (4), a position and attitude sensor (5), and a two-dimensional servo rotation mechanism (6); among which, The terahertz beam waveguide tracking antenna (1) is connected to the two-dimensional servo rotation mechanism (6); The terahertz beam waveguide tracking antenna (1) receives the terahertz signal transmitted by the target, obtains the terahertz sum signal and the terahertz difference signal based on the terahertz signal, and transmits the terahertz sum signal and the terahertz difference signal to the terahertz dual-channel receiver (2). The terahertz dual-channel receiver (2) receives the terahertz sum signal and the terahertz difference signal, performs down-conversion of the terahertz sum signal and the terahertz difference signal to intermediate frequency (IF) respectively to obtain the IF sum signal and the IF difference signal, and transmits the IF sum signal and the IF difference signal to the angle tracking receiver (3). The angle tracking receiver (3) receives the intermediate frequency sum signal and the intermediate frequency difference signal, obtains the error angle signal based on the intermediate frequency sum signal and the intermediate frequency difference signal, and transmits the error angle signal to the tracking controller (4). The position and attitude sensor (5) measures the position and attitude value in real time and transmits the position and attitude value to the tracking controller (4). The tracking controller (4) receives the error angle signal and position attitude value, obtains the compensation error angle based on the error angle signal and position attitude value, and controls the two-dimensional servo rotation mechanism (6) to rotate based on the compensation error angle to achieve target tracking; The terahertz beam waveguide tracking antenna (1) includes a main reflector (11), a sub-reflector (12), a beam waveguide quasi-optical front end, and a single-pulse feed (17); wherein, The terahertz signal emitted by the target is fed into the single-pulse feed source (17) through the main reflector (11), the sub-reflector (12) and the beam waveguide quasi-optical front end in sequence. The single-pulse feed (17) obtains the terahertz sum signal and the terahertz difference signal based on the terahertz signal; The beam waveguide collimating optical front end includes a first frequency-selective surface mirror (13), a first ellipsoidal mirror (14), a second ellipsoidal mirror (15), a second frequency-selective surface mirror (16), a first terahertz absorbing material (18), and a second terahertz absorbing material (19); wherein, The first terahertz absorbing material (18) is disposed at the rear of the first frequency-selective surface reflector (13); The second terahertz absorbing material (19) is disposed at the rear of the second frequency-selective surface reflector (16); The terahertz signal reflected by the sub-reflector (12) is reflected by the first frequency-selective surface mirror (13) and then reaches the first ellipsoidal mirror (14). After being reflected by the first ellipsoidal mirror (14), it reaches the second ellipsoidal mirror (15). After being reflected by the second ellipsoidal mirror (15), it reaches the second frequency-selective surface mirror (16). After being reflected by the second frequency-selective surface mirror (16), it is fed into the single-pulse feed source (17).

2. The space terahertz communication beam tracking device based on beam waveguide according to claim 1, characterized in that: The main reflector (11), the secondary reflector (12) and the first frequency-selective surface reflector (13) are disposed at the pitch axis rotor end of the two-dimensional servo rotation mechanism (6); The pitch axis, the first ellipsoidal reflector (14), the second ellipsoidal reflector (15) and the second frequency-selective surface reflector (16) of the two-dimensional servo rotation mechanism (6) are disposed at the azimuth axis rotor end of the two-dimensional servo rotation mechanism (6). The electric axis of the single-pulse feed (17) is coaxial with the orientation axis of the two-dimensional servo rotation mechanism (6).

3. The space terahertz communication beam tracking device based on beam waveguide according to claim 1, characterized in that: The error angle signal includes the target-antenna electrical axis crossing elevation error angle and the pitch error angle signal. and .

4. The space terahertz communication beam tracking device based on beam waveguide according to claim 3, characterized in that: The target-antenna electrical axis crossing elevation error angle and elevation error angle signals are obtained using the following formulas: ； in, The signal represents the pitch error angle between the target and the antenna's electrical axis. The signal represents the pitch error angle between the target and the antenna's electrical axis. The normalized difference slope constant in the cross-pitch direction. The normalized difference slope constant in the pitch direction. The off-axis error angle of the target deviation from the electric axis of the single-pulse feed source; This represents the off-axis error angle phase.

5. The space terahertz communication beam tracking device based on beam waveguide according to claim 1, characterized in that: The target-antenna electrical axis crossing pitch error angle and pitch error angle are obtained by the following formulas: ； in, The pitch error angle is the angle between the target and the antenna's electrical axis. The target and antenna electrical axis pitch error angle, The phase difference caused by the real-time position of the azimuth and elevation directions of the terahertz beam waveguide tracking antenna (1) The signal represents the pitch error angle between the target and the antenna's electrical axis. The signal represents the pitch error angle between the target and the antenna's electrical axis. The normalized difference slope constant in the cross-pitch direction. is the normalized difference slope constant in the pitch direction.

6. The space terahertz communication beam tracking device based on beam waveguide according to claim 1, characterized in that: The compensation error angle is obtained by the following formula: ； in, The error angle that needs to be compensated for on the azimuth axis of the two-dimensional servo rotation mechanism (6) is as follows. The pitch axis of the two-dimensional servo rotation mechanism (6) needs to be compensated for the error angle. The angle between the azimuth plane of the two-dimensional servo rotation mechanism (6) and the cross elevation plane of the terahertz beam waveguide tracking antenna (1) is given. The pitch error angle is the angle between the target and the antenna's electrical axis. The pitch error angle between the target and the antenna's electrical axis.

7. A method for beam tracking in space terahertz communication based on beamguides, as described in any one of claims 1-6, characterized in that... include: Step S100: Calibrate the space terahertz communication beam tracking device based on beam waveguide; Step S200: The calibrated beamguide-based spatial terahertz communication beam tracking device coarsely points to the target; Step S300: After the coarse pointing is completed, if the angle tracking receiver (3) reports that the target has not been captured, the calibrated space terahertz communication beam tracking device based on beam waveguide updates the coarse pointing angle of the terahertz beam waveguide tracking antenna (1), and performs dynamic spiral scanning search with the half beam width of the terahertz beam waveguide tracking antenna (1) as the step, until the angle tracking receiver (3) reports that the target has been captured. Step S400: The calibrated space terahertz communication beam tracking device based on the beam waveguide is calculated in real time by the tracking controller (4) according to the error angle signal output by the angle tracking receiver (3), and the two-dimensional servo rotation mechanism (6) is controlled to compensate for the error angle, so that the terahertz beam waveguide tracking antenna (1) can point to the target in real time to achieve dynamic tracking. Step S500: If the dynamically tracked target is lost, return to step S200.

8. The spatial terahertz communication beam tracking method based on beam waveguide according to claim 7, characterized in that: In step S300, if the target is not captured after a preset number of spiral scan searches, a noise reduction search is performed until the target is captured.

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