Receiving and transmitting common optical axis antenna system based on liquid crystal phased array

Abstract

The invention discloses a receiving and transmitting common-optical-axis antenna system based on a liquid crystal phased array. The receiving and transmitting common-optical-axis antenna system comprises an optical antenna subsystem, a signal transmitting subsystem and a signal receiving subsystem. The optical antenna subsystem comprises an antenna lens group, a liquid crystal optical phased array device, and a transmitting channel and a receiving channel which share the same optical axis; the antenna lens group is arranged above the liquid crystal optical phased array device and is used for transmitting the transmitted signal light and reflecting the received signal light; the transmitting channel is arranged in the central area of the liquid crystal optical phased array device, and the receiving channel is coaxially arranged in the peripheral area of the liquid crystal optical phased array device; the liquid crystal optical phased array device dynamically changes the polarization states of the emitted light beam and the received light beam through the LCPG controller so as to realize light path separation; the signal emission subsystem is used for emitting and processing emission signal light, and the emission signal light enters the optical antenna subsystem to be processed and then emits an optical signal; and the signal receiving subsystem is used for receiving the received signal light obtained from the optical antenna subsystem and processing the received signal light to obtain a corresponding detection signal.

Description

Technical Field

[0001] This invention belongs to the field of space laser communication technology, specifically relating to a transceiver coaxial antenna system based on a liquid crystal phased array. Background Technology

[0002] In free-space optical communication systems, when establishing a communication link between satellites, the actual positions of the transmitting and receiving terminals deviate from their initial positions during signal propagation due to the vast distance between them and the high-speed relative motion. Therefore, the transmitting end must perform advance aiming, introducing a precisely calculated advance offset angle for the transmitted beam based on the real-time relative positions and velocity vectors of the two terminals. Liquid crystal phased arrays, with their non-mechanical, inertia-free electronically controlled beam deflection capabilities, can correct the beam direction in real time with extremely high speed and accuracy, perfectly meeting this technical requirement. Therefore, how to collaboratively achieve high-efficiency, high-stability transceiver functions based on liquid crystal phased arrays within the limited terminal structure size has become a key system architecture design problem.

[0003] To achieve high-quality bidirectional communication, traditional solutions employ a spatially separated transmit and receive duplex architecture, the core concept of which is a "diameter-separated" design, such as... Figure 1 As shown, this design physically separates the transmitting and receiving optical paths, equipping them with their own independent optical phased array modules, optical windows, and back-end processing circuitry. Specifically, the transmitting channel has a dedicated beam control unit responsible for precise signal transmission; the receiving channel is equipped with an independent optical window and detection system specifically for capturing optical signals from a distant location. This physically isolated architecture avoids mutual interference between the transmitting and receiving optical paths, reducing system crosstalk.

[0004] However, in scenarios with extremely stringent requirements for parameters such as size, weight, thermal stability, reliability, lifespan, and power consumption, the duplex communication architecture of traditional liquid crystal phased array transceiver antennas suffers from the following problems: ① Low system integration: The system structure is complex and bulky, alignment is complicated, system lifespan is short, and power consumption is relatively high. ② Low aperture utilization: Necessary physical spacing must be maintained between the transmitting and receiving modules, resulting in reduced system aperture utilization. ③ Poor control coordination: The two modules need to be configured and controlled independently, leading to poor device consistency, thermal stability, and response coordination. Especially in scenarios requiring high-speed response and high-precision beam alignment, there are significant challenges to system stability and reliability.

[0005] Therefore, there is an urgent need to provide a transceiver coaxial antenna system based on a liquid crystal phased array, which can ensure the stability and reliability of the system while taking into account the size of the communication terminal. Summary of the Invention

[0006] The purpose of this invention is to provide a transceiver coaxial antenna system based on a liquid crystal phased array, which integrates the transmitting and receiving channels into the same liquid crystal optical phased array system to achieve a common aperture for both transmitting and receiving, thereby improving the aperture utilization efficiency of the system. Moreover, the communication architecture is coaxial and can achieve optical path separation, thereby improving stability and reliability.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A coaxial antenna system based on a liquid crystal phased array includes an optical antenna subsystem, a signal transmission subsystem, and a signal reception subsystem.

[0009] The optical antenna subsystem includes an antenna mirror group, a liquid crystal optical phased array device, and a transmit channel and a receive channel arranged coaxially. The antenna mirror group is positioned above the liquid crystal optical phased array device and is used to transmit the transmitted signal light and reflect the received signal light. The transmit channel is located in the central region of the liquid crystal optical phased array device, while the receive channel is located in the peripheral region. The liquid crystal optical phased array device dynamically changes the polarization state of the transmitted and received beams through an LCPG controller to achieve optical path separation.

[0010] The signal transmitting subsystem is used to emit and process the transmitted signal light. The transmitted signal light enters the optical antenna subsystem for processing and then emits the optical signal.

[0011] The signal receiving subsystem is used to receive the received signal light obtained from the optical antenna subsystem and process it to obtain the corresponding detection signal.

[0012] The difference between this invention and existing technologies lies in the fact that, without affecting communication performance, this system designs the duplex architecture of the originally spatially separated transmit and receive channels on the same liquid crystal optical phased array panel (specifically, the central area is used for signal transmission, and the outer area is used for signal reception, thus forming a spatially symmetrical and highly integrated system). This achieves a common optical axis design and realizes spatial multiplexing of transmit and receive functions through program partitioning control. This common optical axis structure significantly improves aperture utilization and system integration, and simplifies packaging, thermal management, and alignment debugging processes.

[0013] Preferably, the cascaded liquid crystal phased array comprises N cascaded unit polarization gratings, wherein the deflection angle of each subsequent unit polarization grating is twice the deflection angle of the preceding unit polarization grating, and N is a positive integer. The deflection angles of each stage form a geometric sequence. The cascaded liquid crystal phased array, composed of N unit polarization gratings, can achieve 2 N If the deflection angle is N, then the field of view of the system is determined by the number N of the cascaded unit polarization gratings.

[0014] Preferably, the antenna mirror assembly adopts a primary and secondary mirror structure of a cassette telescope, wherein the primary mirror is a large parabolic reflector with a central opening and is located at the rear end of the system, and the secondary mirror is a hyperboloid mirror located near the focal point of the primary mirror and facing the primary mirror. During transmission, the light signal is emitted from the central opening of the primary mirror, transmitted through the secondary mirror, and then emitted outward. During reception, the parallel beam of light is reflected by the primary mirror and converged to the vicinity of its focal point, then reflected a second time by the secondary mirror, and enters the signal receiving subsystem through the central opening of the primary mirror.

[0015] Preferably, the signal transmission optical path is as follows: After the signal light of the signal transmission subsystem is emitted from the transmitting optical fiber, it is collimated by a shaping lens and then converted into O-light by a transmitting polarization filter. The O-light is reflected by a polarization beam splitter and a precision aiming mirror, and then enters the optical antenna subsystem. Subsequently, the beam is deflected by a cascaded liquid crystal phased array and finally converted into circularly polarized light by a quarter-wave plate at the bottom layer, thus transmitting the optical signal.

[0016] Signal receiving optical path: The received signal light is first converted into linearly polarized light by a quarter-wave plate; then it passes through a cascaded liquid crystal phased array and is compressed by an optical antenna, and is then reflected by the precision aiming mirror; the reflected E light is transmitted through the polarization beam splitter, and then passes through the intensity beam splitter and the receiving polarization filter in sequence before being focused by the signal receiving lens and coupled into the signal receiving optical fiber.

[0017] Preferably, the aperture of the launch channel is the same as that of the secondary mirror.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] 1. Abandoning the traditional physical separation design, instead, the same liquid crystal optical phased array panel is divided into functionally independent transmitting area (center) and receiving area (outer ring) to achieve a common aperture for transmitting and receiving. The liquid crystal optical phased array panel is partitioned and controlled by an LCPG controller to dynamically change the polarization state of the transmitted and received beams, thereby achieving optical path separation and ultimately realizing spatial multiplexing and integration of transmitting and receiving functions.

[0020] 2. The transceiver aperture of the present invention is coaxial, with a compact structure, which greatly reduces the size of the communication terminal and reduces power consumption; at the same time, it improves the aperture utilization efficiency of the system; and the coaxial communication architecture has better functional synergy and can realize optical path separation, which improves the thermal stability and reliability of the system.

[0021] 3. The optical antenna adopts a cassette telescope structure, which not only has a relatively large field of view for the primary mirror, which is conducive to acquisition and tracking, but also makes it easy to achieve dual-band / multi-functional common aperture; at the same time, it has the characteristics of high performance and high reliability.

[0022] 4. This system does not rely on different wavelengths for communication. Instead, by introducing coherence isolation (the polarization state of the beam can be dynamically changed between the central transmitting region and the outer ring receiving region, so that the transmitting and receiving beams have different polarization states, thus having a certain degree of coherence isolation), it has the ability to achieve synchronous transmission and reception without interference at the same wavelength, which greatly simplifies the system design. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of a traditional space-based transceiver-separated duplex antenna structure.

[0024] Figure 2 This is a schematic diagram of the antenna structure of a transceiver coaxial antenna system based on a liquid crystal phased array according to the present invention.

[0025] Figure 3 This is a schematic diagram of the transceiver coaxial antenna system based on a liquid crystal phased array according to the present invention.

[0026] Figure 4 This is a schematic diagram of the liquid crystal phased array of the present invention.

[0027] Figure 5 This is a schematic diagram of the operation of the liquid crystal optical phased array of the present invention. Detailed Implementation

[0028] To make the objectives and advantages of the present invention clearer, the present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0029] like Figure 2 , 3 As shown, the present invention is a transceiver coaxial antenna system based on a liquid crystal phased array, comprising an optical antenna subsystem, a signal transmission subsystem, and a signal reception subsystem.

[0030] The optical antenna subsystem includes an antenna mirror assembly, a liquid crystal optical phased array device, and a coaxial transmission and reception channel. The antenna mirror assembly is positioned above the liquid crystal optical phased array device and is used to transmit transmitted signal light and reflect received signal light. Specifically, the line mirror assembly adopts a primary and secondary mirror structure similar to a Cassette telescope. The primary mirror is a large parabolic reflector with a central opening, located at the rear of the system. The secondary mirror is a hyperboloid mirror located near the focal point of the primary mirror, directly opposite it. When the signal light is transmitted, the light signal exits from the central opening of the primary mirror, is transmitted through the secondary mirror, and then emitted outwards. When the signal light is received, the parallel beam is reflected by the primary mirror and converges to its focal point. After a second reflection by the secondary mirror, it enters the signal receiving subsystem through the central opening of the primary mirror.

[0031] The transmitting channel is located in the central region of the liquid crystal optical phased array device, while the receiving channel is coaxially located in the peripheral region of the liquid crystal optical phased array device. Figure 2As shown, this channel design scheme achieves coaxial transmission and reception, constructing a highly integrated, low-redundancy coaxial duplex communication system. The coaxial structure significantly improves aperture utilization and system integration, and simplifies packaging, thermal management, and alignment debugging processes. Especially in multi-channel systems, this scheme easily ensures optical path coordination and optical axis coincidence, thereby effectively improving dynamic alignment accuracy, communication stability, and energy transmission efficiency.

[0032] To achieve both transmission and reception functions on a single panel, this invention utilizes the anisotropic refractive index of liquid crystals in a liquid crystal optical phased array (LCPG) to modulate beam deflection. Furthermore, its high resolution and pixel-level independent driving capability enable partitioned control on the same panel to complete the system's transmission and reception functions. Specifically, the LCPG device dynamically changes the polarization states of the transmitted and received beams through an LCPG controller to achieve optical path separation (coherent isolation). Through region mapping and logical configuration during the initialization phase, the central region is defined as the transmitting antenna, and the outer ring region as the receiving antenna, thus constructing a programmatic division-of-labor duplex communication system. This achieves spatial multiplexing and integration of transmission and reception functions while ensuring spatial isolation between the transmitting and receiving channels. Additionally, this system does not rely on different wavelengths for communication; instead, by setting coherent isolation, it achieves synchronous transmission and reception at the same wavelength without interference.

[0033] The signal transmission optical path of this system is as follows: After the signal light exits from the transmitting fiber in the signal transmission subsystem, it is collimated by a shaping lens and then converted into O-light by a transmitting polarization filter. This O-light is reflected by a polarizing beam splitter and a precision aiming mirror before entering the optical antenna subsystem. Subsequently, the beam is deflected by a cascaded liquid crystal phased array, and finally converted into circularly polarized light by a quarter-wave plate at the bottom, thus transmitting the optical signal. The signal transmitting fiber can move two-dimensionally along the vertical optical axis, enabling pre-aiming.

[0034] The signal receiving optical path of this system is as follows: The received signal light is first converted into linearly polarized light (E-beam) by a quarter-wave plate; then it passes through a cascaded liquid crystal phased array and is compressed by an optical antenna, before being reflected by the precision aiming mirror. The reflected E-beam is transmitted through the polarization beam splitter, then sequentially through an intensity beam splitter and a receiving polarization filter. Finally, the beam is focused by the signal receiving lens and coupled into the signal receiving optical fiber, transmitting to the photosensitive surface of the detector to complete the detection. The receiving polarization filter is used to eliminate stray light generated by the laser, especially the back-reflected light from the optical antenna.

[0035] like Figure 4 As shown, the cascaded liquid crystal phased array includes N cascaded unit polarization gratings. The deflection angle of the subsequent unit polarization grating is twice the deflection angle of the preceding unit polarization grating. The target field of view is a=b. 2 N Here, b is the deflection angle of the first-level unit polarization grating, and N is a positive integer. The value of N is determined by the required field of view (target field of view) in the actual application. For example, when the minimum deflection direction is ±0.75° and the target field of view is ±12°, the number of cascaded gratings N=4; while when the minimum deflection direction is ±0.75° and the target field of view is ±24°, the number of cascaded gratings N=5. In the cascaded structure of a liquid crystal phased array, the deflection angle of the first-level polarization grating determines the scanning accuracy of the entire system. Figure 5 As shown, the deflection angle of the first-order unit polarization grating is ±0.75°, the deflection angle of the second-order unit polarization grating is ±1.50°, the deflection angle of the third-order unit polarization grating is ±3.0°, and the deflection angle of the fourth-order unit polarization grating is ±6.0°.

[0036] Based on the geometric progression relationship between the deflection angles of the preceding and following stages, if the system consists of N unit polarization gratings, then theoretically, it can achieve 2 N The deflection angle is determined by the number of cascaded gratings, N. For example, when the minimum deflection direction is ±0.75° and the target field of view is ±12°, the number of cascaded gratings, N=4, and the number of deflection angles achievable is 2. N =16. If the system's field of view needs to be increased, simply cascade it at a later stage.

[0037] To achieve integrated transceiver design with a common optical axis and ensure lossless communication performance after integration, the structural equivalence must be rigorously defined at the physical modeling level. The core criterion is "area equivalence," which requires that the energy transmission capacity of the transmit and receive channels of the common optical axis system, per aperture area, must be consistent with that of the split-aperture system. At its core optical level, in free-space optical communication, regardless of whether it's a split-aperture or common optical axis structure, the final performance of the system depends on two physical quantities directly determined by geometric area: the far-field divergence angle and the received power.

[0038] For the transmission channel, its core performance indicators are the far-field main lobe width, beam divergence angle, and energy concentration, which determine the system's pointing accuracy and link stability. According to Fresnel-Kirchhoff diffraction theory, for a beam with an ideal circular aperture, its far-field main lobe width... With wavelength The aperture diameter D satisfies the following approximate relationship:

[0039]

[0040] Therefore, if the actual aperture diameter (or equivalent area) of the transmission channel remains consistent, its far-field beam angle distribution remains unchanged, and the spatial energy density is consistent with the main lobe characteristics. Thus, as long as the diameter of the central emission aperture in the coaxial structure is equal to the emission aperture in the aperture-splitter system, the far-field beam performance is completely equivalent and can be considered as equivalent transmission channels.

[0041] For the receiving channel, the system focuses on its ability to collect optical flux from external signals and its signal-to-noise ratio. In free space, far-field light intensity is generally approximately quasi-uniformly distributed, and the total power received by the receiver... With the effective area of ​​reception A linear relationship exists:

[0042]

[0043] in Let be the incident light intensity density. Therefore, reducing the receiver aperture area will directly lead to a decrease in received signal power, thereby affecting the communication signal-to-noise ratio and bit error rate. Thus, during aperture integration, as long as the area of ​​the receiver loop is not less than the receiving area of ​​the multi-aperture system, the overall system performance can be maintained in balance.

[0044] The caliber system employs two independent caliber configurations, with the corresponding area of ​​the transmitting caliber being:

[0045]

[0046] The area corresponding to the receiving aperture is:

[0047]

[0048] In the coaxial system of this invention, the overall structure uses a single circular optical panel, with an opening in the central area for emission and an outer annular area for reception. At this time:

[0049] The diameter of the launch aperture (central circular aperture) remains d, and the launch area remains unchanged.

[0050]

[0051] The receiving area is an outer ring-shaped region with an area of:

[0052]

[0053] Therefore, to maintain the same transmitting aperture, the receiving area of ​​a coaxial structure is the same as that of a transceiver separation system, which only requires determining the outer ring diameter D (receiving channel aperture). If the outer diameter cannot be increased due to structural or manufacturing limitations, comprehensive compensation is needed at the system design level, such as improving the response sensitivity of the photodetector, using a low-noise amplifier, and optimizing the beam coupling mechanism, to ensure that the overall performance of the system communication link is not compromised.

[0054] To meet the application requirements of communication terminals in scenarios such as spaceborne co-orbiting, low-altitude mobile platforms, and fixed points on high-altitude buildings, this invention can achieve the desired results by adjusting the size of the transmitting / receiving aperture, and the number of liquid crystal phased arrays, liquid crystal polarization gratings, and liquid crystal waveplates. Compared to separate transceiver schemes, to achieve equal received energy, in this preferred embodiment, the transmitting channel aperture is designed to be the same as the secondary mirror aperture. If the transmitting channel aperture is smaller than the secondary mirror aperture, the transmitted beam cannot pass entirely through the transmitting channel; if the transmitting channel aperture is larger than the secondary mirror aperture, a portion of the central transmitting area of ​​the phased array will be unused, and the diameter of the receiving area will also be larger, reducing utilization. This design results in higher phased array utilization without affecting the use of the card-type antenna.

[0055] The transmit and receive channel diameters can be adjusted according to different application scenarios. For example, in a certain scenario, in a split structure, the transmit diameter is d = 40 mm, the receive diameter is D' = 80 mm, and the receiving area is 5026.55 mm². 2 To ensure that the area of ​​the transmitting and receiving parts remains unchanged, the diameter of the transmitting center circle in this invention is 40mm, while the diameter of the receiving outer circle can be 90mm to guarantee a receiving area of ​​5026.55 mm². 2 For applications requiring a separate structure with a transmitter aperture of d=40mm and a receiver aperture of 100mm, the transmitter aperture of this invention is 40mm, and the outer circle diameter is 108mm.

[0056] The above embodiments are merely specific examples to further illustrate the purpose, technical solution, and beneficial effects of the present invention, and the present invention is not limited thereto. Any modifications, equivalent substitutions, improvements, etc., made within the scope of the disclosure of the present invention are included within the protection scope of the present invention.

Claims

1. A transceiver coaxial antenna system based on a liquid crystal phased array, characterized in that: It includes an optical antenna subsystem, a signal transmitting subsystem, and a signal receiving subsystem; The optical antenna subsystem includes an antenna mirror group, a liquid crystal optical phased array device, and a transmit channel and a receive channel arranged coaxially. The antenna mirror group is positioned above the liquid crystal optical phased array device and is used to transmit transmitted signal light and reflect received signal light. The transmit channel is located in the central region of the liquid crystal optical phased array device, and the receive channel is coaxially located in the peripheral region of the liquid crystal optical phased array device, or the receive channel is located in the central region of the liquid crystal optical phased array device, and the transmit channel is coaxially located in the peripheral region of the liquid crystal optical phased array device. Liquid crystal optical phased array devices achieve optical path separation by dynamically changing the polarization state of the emitted and received beams through an LCPG controller; The signal transmitting subsystem is used to emit and process the transmitted signal light. The transmitted signal light enters the optical antenna subsystem for processing and then emits the optical signal. The signal receiving subsystem is used to receive the received signal light obtained from the optical antenna subsystem and process it to obtain the corresponding detection signal.

2. The transceiver coaxial antenna system based on a liquid crystal phased array according to claim 1, characterized in that: The cascaded liquid crystal phased array includes N cascaded unit polarization gratings, where the deflection angle of the subsequent unit polarization grating is twice the deflection angle of the preceding unit polarization grating, and N is a positive integer.

3. The coaxial transceiver antenna system based on a liquid crystal phased array according to claim 1, characterized in that: The antenna mirror assembly adopts a primary and secondary mirror structure of a cassette telescope. The primary mirror is a large parabolic reflector with a central opening, located at the rear of the system. The secondary mirror is a hyperboloid mirror located near the focal point of the primary mirror, directly opposite the primary mirror. During transmission, the light signal is emitted from the central opening of the primary mirror, transmitted through the secondary mirror, and then emitted outward. During reception, the parallel beam of light is reflected by the primary mirror and converges to the vicinity of its focal point. After a second reflection by the secondary mirror, it enters the signal receiving subsystem through the central opening of the primary mirror.

4. The transceiver coaxial antenna system based on a liquid crystal phased array according to any one of claims 1-3, characterized in that: The signal light from the signal transmission subsystem is emitted from the transmitting fiber, collimated by a shaping lens, and then converted into O-light by a transmitting polarization filter. The O-light is reflected by a polarization beam splitter and a precision aiming mirror, and then enters the optical antenna subsystem. Subsequently, the beam is deflected by a cascaded liquid crystal phased array, and finally converted into circularly polarized light by a quarter-wave plate at the bottom layer, thus transmitting the optical signal. The received signal light is first converted into linearly polarized light by a quarter-wave plate; then it passes through a cascaded liquid crystal phased array and is compressed by an optical antenna, and is then reflected by the precision aiming mirror; the reflected E-light is transmitted through the polarization beam splitter, and then passes through the intensity beam splitter and the receiving polarization filter in sequence before being focused by the signal receiving lens and coupled into the signal receiving optical fiber.

5. The transceiver coaxial antenna system based on a liquid crystal phased array according to claim 3, characterized in that: The aperture of the launch channel is the same as that of the secondary mirror.

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