Transmissive liquid crystal phased array antenna based on FP resonant cavity

Abstract

The application discloses a transmission type liquid crystal phased array antenna based on an FP resonant cavity and belongs to the technical field of antennas. The transmission type liquid crystal phased array antenna comprises a liquid crystal transmission array layer, a first air layer, a partially reflective surface layer, a second air layer, an antenna radiation layer and an antenna feed layer. The liquid crystal transmission array layer is composed of a plurality of frequency selective surface transmission unit cycles arranged in a periodical mode. Double-layer liquid crystal layers are arranged in the transmission unit. Patch type FSS units and slot type FSS units are arranged above and below the liquid crystal layers respectively. The direct current microstrip bias lines of the patch type FSS units in the same column are communicated. The partially reflective surface layer and the antenna radiation layer form the upper and lower reflective interfaces of the FP resonant cavity respectively. The antenna feed layer adopts a multi-stage T-shaped power divider matched with a slot coupling feed. The liquid crystal transmission array layer is introduced above the FP resonant cavity body. Phase compensation can be realized by using only a small amount of bias lines. Meanwhile, the high gain characteristics of the FP resonant cavity are utilized. In combination with the electric field regulation of the liquid crystal dielectric constant, high gain one-dimensional beam scanning within the range of ±45 degrees is finally realized.

Description

Technical Field

[0001] This invention belongs to the field of antenna technology and relates to a transmissive liquid crystal phased array antenna based on an FP resonant cavity. More specifically, in response to the urgent need for high gain, high integration, miniaturization, and continuously adjustable beam of phased array antennas, a transmissive liquid crystal phased array antenna with a multi-layer frequency selective surface (M-FSS) liquid crystal phased array and an FP high-gain resonant cavity is proposed. Background Technology

[0002] Nematic liquid crystals are liquid crystal phases with low viscosity and fast response speed. They maintain good stability over a wide temperature range, and the liquid crystal molecules can rotate along the normal direction of the liquid crystal layer under the influence of an applied electric field, enabling effective control of the liquid crystal's equivalent dielectric constant. Based on these characteristics, nematic liquid crystals have become the preferred material for liquid crystal antenna design in the microwave field.

[0003] Phased array antennas based on liquid crystal dielectric modulation are a potential antenna design solution that can achieve low cost, miniaturization, and low profile requirements. The design of liquid crystal phased array antennas is mainly divided into three categories: reflective, planar phase-shifting, and transmissive. In reflective liquid crystal phased array antennas, the feed and the modulated reflected wave are on the same side, resulting in a feed blocking effect and causing certain scanning blind spots. Planar phase-shifting liquid crystal phased array antennas require the introduction of microstrip delay line structures, which are difficult to design and have high transmission losses. Transmissive liquid crystal phased array antennas, on the other hand, have advantages such as high gain, simple design, and easy fabrication, while avoiding the feed blocking problem of reflective antennas, and are gradually becoming a research hotspot.

[0004] A multi-layer frequency selective surface (M-FSS) is a type of array structure for transmission array antennas. It consists of several cascaded frequency selective surfaces with the same configuration, separated by air or a substrate. The stacking of multiple FSSs significantly broadens the operating bandwidth of the transmission elements, effectively increasing the phase shift of the element S21 while maintaining transmission performance, and achieving higher radiation efficiency. The M-FSS structure balances antenna performance and design convenience, making it more advantageous and promising in transmission array antenna designs.

[0005] The FP resonant cavity antenna is a high-gain transmission antenna, mainly composed of a metal ground plane, a feed antenna, and a partial reflector surface (PRS). In practical design and application, the antenna feed is usually placed on the lower surface of the cavity. The electromagnetic waves radiated by the feed are continuously reflected and transmitted between the lower metal ground plane and the upper PRS. Simultaneously, the radiated electromagnetic waves gradually spread from the center to the edge, increasing the antenna's radiating aperture. When the height distance between the upper PRS and the lower metal ground plane meets the resonance condition, the electromagnetic waves transmitted from bottom to top will produce in-phase interference superposition effects, ultimately increasing the antenna's normal transmission gain.

[0006] Most existing transmissive liquid crystal phased array antennas operate in frequencies above 30 GHz and even in the terahertz band, while designs for transmissive liquid crystal phased array antennas in the X-band are extremely rare. Furthermore, current research on transmissive liquid crystal phased array antennas generally suffers from an excessive number of DC bias lines, making it difficult to perform liquid crystal dielectric manipulation in practical applications, and resulting in a narrow one-dimensional beam scanning range. Therefore, it is necessary to research a transmissive liquid crystal phased array antenna that operates in the X-band, offers convenient liquid crystal dielectric manipulation, and has a wide beam scanning range. Summary of the Invention

[0007] To address the problems of excessive DC bias lines in existing transmissive liquid crystal phased array antennas, which lead to difficulties in liquid crystal dielectric modulation and narrow one-dimensional beam scanning range, this invention provides a transmissive liquid crystal phased array antenna based on an FP resonator. Its operating frequency band is located in the X-band. By introducing an M-FSS liquid crystal transmissive array layer above the FP resonator, the complex structure that originally required a large number of bias lines is simplified to phase compensation with only a few bias lines. At the same time, by utilizing the high gain characteristics of the FP resonator and combining it with the electric field modulation of the liquid crystal dielectric constant, high-gain one-dimensional beam scanning within a range of ±45° is finally achieved.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A transmissive liquid crystal phased array antenna based on an FP resonant cavity is characterized in that it operates in the X-band and includes, from top to bottom, a liquid crystal transmissive array layer, a first air layer, a partially reflective surface layer, a second air layer, an antenna radiating layer, and an antenna feed layer.

[0010] The liquid crystal transmission array layer is composed of a two-dimensional periodic arrangement of multiple frequency selective surface (M-FSS) transmission units; a single transmission unit includes a first dielectric substrate, a first patch-type FSS unit, a first liquid crystal layer, a first slit-type FSS unit, a second dielectric substrate, a second slit-type FSS unit, a second liquid crystal layer, a second patch-type FSS unit, and a third dielectric substrate stacked from top to bottom.

[0011] Both the first surface-mount FSS unit and the second surface-mount FSS unit are provided with a DC microstrip bias line running through the center of the surface-mount unit. The DC microstrip bias lines in the same column are interconnected to apply a bias voltage to all surface-mount FSS units in the same column simultaneously. The first slit FSS unit and the second slit FSS unit cooperate with the surface-mount FSS units on the same side to clamp the liquid crystal layer, forming a double-layer liquid crystal phase-shifting structure. By applying differentiated bias voltages to each column of surface-mount FSS units, the equivalent dielectric constant of the liquid crystal layer in the corresponding region is adjusted, thereby achieving electromagnetic wave transmission phase compensation.

[0012] The partially reflective surface layer includes a fourth dielectric substrate and a plurality of first metal patch units arranged in a two-dimensional periodic pattern on its upper surface; the partially reflective surface layer serves as the upper reflective interface of the FP resonant cavity, providing the upper cavity reflection phase required for the coherent superposition of electromagnetic waves.

[0013] The antenna radiating layer includes a fifth dielectric substrate, a microstrip patch radiating element array disposed on the upper surface of the fifth dielectric substrate, and a second metal patch element periodically arranged around each radiating element; the microstrip patch radiating element array and the second metal patch element together constitute the lower phase reflection interface of the FP resonant cavity, providing the lower cavity reflection phase required for the coherent superposition of electromagnetic waves.

[0014] The antenna feed layer includes a sixth dielectric substrate. The lower surface of the sixth dielectric substrate is provided with a one-to-many microstrip power divider, and the upper surface is provided with a slotted metal ground. The one-to-many microstrip power divider is composed of multiple T-type one-to-two microstrip power dividers cascaded together to achieve equal power distribution of the feed energy. The slotted metal ground has rectangular coupling slots that are directly opposite each microstrip patch radiating element to longitudinally couple and transmit electromagnetic wave energy to the radiating elements above.

[0015] Furthermore, both the first and second surface-mount FSS units adopt a 45° rotated Jerusalem cross-shaped metal surface-mount configuration;

[0016] Both the first and second slotted FSS units have Jerusalem cross-shaped perforated slots.

[0017] Furthermore, the microstrip patch radiating unit array includes four square patch radiating units with identical structures and uniform distribution; the one-to-many microstrip power divider is a one-to-four microstrip power divider.

[0018] Furthermore, in the aforementioned one-to-four microstrip power divider, the right-angle bends of the microstrip lines are chamfered.

[0019] Furthermore, the first metal patch unit is a square metal patch, a square annular metal patch, a circular metal patch, or an annular metal patch.

[0020] Furthermore, the second metal patch unit is a square metal patch, a square annular metal patch, a circular metal patch, or an annular metal patch.

[0021] Furthermore, the thickness of the first liquid crystal layer and the second liquid crystal layer ranges from 0.254 mm to 0.508 mm.

[0022] This invention employs slot-coupled feeding for the antenna; the 1-to-4 microstrip power divider in the antenna feed layer transmits energy longitudinally to the antenna radiating patch through the slotted metal ground above. This design overcomes the wiring difficulties caused by the feed line and the radiating source being on the same layer in traditional side-feed schemes, and also avoids the problems of a large number of feed source interfaces and the difficulty in installing feed source interfaces in traditional back-feed schemes.

[0023] The FP resonant cavity has two-dimensional periodic arrangement of different forms of metal patches on the partial reflective surface layer of the upper cavity and around the radiation source of the lower cavity. This can provide the required reflection phase for cavity resonance. The radiated electromagnetic waves will be reflected back and forth multiple times in the cavity, and finally achieve beam in-phase interference superposition at the resonant frequency, resulting in a low sidelobe, high-gain transmission plane wave, which is convenient for subsequent beam scanning phase compensation and control in the liquid crystal transmission array.

[0024] The liquid crystal transmission array in this invention uses two layers of liquid crystal. At the same time, the patch-type Jerusalem cross FSS unit and the slot-type Jerusalem cross FSS unit are used overlapping on both sides of the liquid crystal layer. Each DC bias line controls the dielectric constant of the liquid crystal in the corresponding column of unit regions. Compared with the traditional liquid crystal transmission array structure, it can minimize the number of liquid crystal layers and the corresponding number of DC bias lines used in the structure, reduce the complexity of liquid crystal control, and further reduce the transmission loss of the transmission array, improve the phase transmission response of the array, and finally achieve clear and accurate one-dimensional beam scanning of the main beam.

[0025] The overall structure of the FP resonant cavity-based transmissive liquid crystal phased array antenna proposed in this invention has the advantages of miniaturization, compactness, accurate beam scanning, wide scanning range, and simple liquid crystal control. At the same time, its three-layer planar longitudinally stacked structure significantly reduces the system profile height compared with the traditional air-fed liquid crystal transmissive array antenna, while avoiding the scanning blind spot defect of the horn air-fed antenna structure.

[0026] The beneficial effects of this invention are:

[0027] 1. Compared with existing research, this invention significantly reduces the number of DC bias lines in a transmissive liquid crystal phased array antenna by designing and loading the M-FSS liquid crystal transmissive array, thereby reducing the difficulty of liquid crystal dielectric control in actual antenna fabrication and application.

[0028] 2. This invention adopts a planar microstrip antenna structure design with FP resonant cavity, and achieves a feed normal high gain of 20.96dBi at the center frequency of 10GHz in the X-band; after loading the liquid crystal transmission array layer, the final transmission liquid crystal phased array antenna still has a normal gain of 16.9dBi.

[0029] 3. Simulation results show that, through the combined design of the FP resonant cavity and the M-FSS liquid crystal transmission array structure, the transmission liquid crystal phased array antenna of the present invention achieves a one-dimensional beam scanning of more than 12.37 dBi within a range of ±45°, and is suitable for one-dimensional beam reconfigurable scenarios with high gain, miniaturization and compact design goals. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. It should be noted that the drawings described below are merely embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the overall antenna structure provided in an embodiment of the present invention.

[0032] Figure 2 This is a schematic diagram of the liquid crystal transmission array layer unit structure provided in an embodiment of the present invention.

[0033] Figure 3 This is a top view of the patch-type FSS structure in the liquid crystal transmission array unit provided in an embodiment of the present invention.

[0034] Figure 4 This is a top view of the slit-type FSS structure in the liquid crystal transmission array unit provided in an embodiment of the present invention.

[0035] Figure 5 This is a schematic diagram of a partial reflective surface layer unit structure provided in an embodiment of the present invention.

[0036] Figure 6 This is a schematic diagram of the overall structure of the antenna radiating layer provided in an embodiment of the present invention.

[0037] Figure 7 This is a schematic diagram of a slotted metal ground structure on the upper surface of the antenna feed layer provided in an embodiment of the present invention.

[0038] Figure 8 This is a schematic diagram of a one-to-four microstrip power divider structure on the lower surface of the antenna feed layer provided in an embodiment of the present invention.

[0039] Figure 9 This is a top view of the antenna feed layer lower surface one-to-four microstrip power divider structure provided in an embodiment of the present invention.

[0040] Figure 10 The figures show the simulation results of the E-plane and H-plane gain of the FP resonant cavity antenna in this embodiment of the invention.

[0041] Figure 11 The diagram shows the simulation results of three liquid crystal dielectric constant states and their corresponding S21 transmission amplitude and transmission phase during the phase compensation process of the liquid crystal transmission array in this embodiment of the invention.

[0042] Figure 12 The figure shows the simulation results of the overall S11 return loss of the antenna in this embodiment of the invention.

[0043] Figures 13 to 18 The diagram shows a one-dimensional beam scanning phase compensation diagram and gain simulation results for the antenna pointing at -45°, -30°, -15°, 15°, 30°, and 45°, respectively, in an embodiment of the present invention.

[0044] Explanation of reference numerals in the attached figures: 1. Liquid crystal transmissive array layer; 10. First dielectric substrate; 11. First patch-type FSS unit; 111. Jerusalem cross-shaped metal patch; 112. Liquid crystal DC microstrip bias line. 12. First liquid crystal layer; 13. First slotted FSS unit; 131. Slotted FSS unit copper foil; 132. Jerusalem cross-shaped aperture; 14. Second dielectric substrate; 15. Second slotted FSS unit; 16. Second liquid crystal layer; 17. Second patch FSS unit; 18. Third dielectric substrate; 2. Partially reflective surface layer; 20. Fourth dielectric substrate; 21. Square metal patch; 3. Antenna radiating layer; 30. Fifth dielectric substrate; 31. Square ring metal patch; 32. Microstrip patch antenna unit; 4. Antenna feed layer; 40. Sixth dielectric substrate; 41. Copper foil; 42. Rectangular coupling slot; 43. 1 / 4 microstrip power divider; 431. 50Ω microstrip feed line; 432. 1 / 4 wavelength microstrip impedance matching device; 433. Microstrip line chamfer; 434. Position of feed line and slot at the end of the power divider. Detailed Implementation

[0045] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0046] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0047] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0048] This embodiment provides a transmissive liquid crystal phased array antenna based on an FP resonant cavity, such as... Figure 1 As shown, the antenna includes, from top to bottom, a liquid crystal transmissive array layer, a first air layer, a partial reflective surface layer, a second air layer, an antenna radiating layer, and an antenna feed layer. The liquid crystal transmissive array layer and the partial reflective surface layer are suspended by a support structure, forming an air cavity with a thickness of 30 mm. The partial reflective surface layer and the antenna radiating layer are also suspended by a support structure, forming an air cavity with a thickness of 13 mm. The overall antenna structure dimensions are 120 mm × 120 mm × 49 mm.

[0049] The liquid crystal transmission array layer is composed of a two-dimensional periodic arrangement of multiple frequency selective surface (M-FSS) transmission units, with an array size of 20×20; the corresponding transmission unit structure is as follows: Figure 2 As shown, from top to bottom, the substrate includes a first dielectric substrate, a first surface-mount FSS cell, a first liquid crystal layer, a first slotted FSS cell, a second dielectric substrate, a second slotted FSS cell, a second liquid crystal layer, a second surface-mount FSS cell, and a third dielectric substrate. The first and third dielectric substrates are made of RO4350B with a dielectric constant of 3.66 and a thickness of 30 mil (0.762 mm); the second dielectric substrate is also made of RO4350B with a dielectric constant of 3.66 and a thickness of 60 mil (1.524 mm), and all have a cell period of 6 mm × 6 mm.

[0050] The thickness of both the first and second liquid crystal layers is 10 mil (i.e., 0.254 mm), and the equivalent dielectric constant ε of the selected liquid crystal material is... eff The range of variation is 2.4 to 3.2.

[0051] The first surface mount FSS unit and the second surface mount FSS unit, such as Figure 3As shown, it includes a Jerusalem cross-shaped metal patch and a liquid crystal DC microstrip bias line running through the center of the patch. The DC microstrip bias lines in the same column are interconnected and used to synchronously apply bias voltage to all surface-mount FSS cells in the same column. The Jerusalem cross-shaped metal patch consists of a main branch with an orthogonal cross shape rotated at 45° and four rectangular sub-branches extending from the ends of the main branch. The length and width of the two rectangular patches in the main branch are 4.5 mm and 1.5 mm, respectively, and the length and width of the four rectangular patches in the sub-branches are 2 mm and 0.5 mm, respectively. The line width of the liquid crystal DC microstrip bias line is 0.1 mm.

[0052] The first slotted FSS unit and the second slotted FSS unit, such as Figure 4 As shown, it includes a copper foil covering the surface of a second dielectric substrate and a Jerusalem cross-shaped aperture opened at the center of the copper foil; the thickness of the copper foil is 0.035 mm; the Jerusalem cross-shaped aperture consists of an orthogonal cross-shaped main slit and four rectangular sub-slits extending from the ends of the main slit, wherein the length and width of the two rectangular apertures constituting the main slit are 2.5 mm and 0.5 mm, respectively, and the length and width of the four rectangular sub-slits are 2 mm and 0.3 mm, respectively.

[0053] The partially reflective surface layer includes a fourth dielectric substrate and a square metal patch disposed on the upper surface of the fourth dielectric substrate; such as Figure 5 As shown, the fourth dielectric substrate is made of RO4350B with a dielectric constant of 3.66 and a thickness of 1.524 mm; the square metal patch is used to provide the upper reflection phase required by the FP resonant cavity, and the side length of the square metal patch is 7 mm; the unit period of the partial reflective surface layer is 7.5 mm × 7.5 mm.

[0054] The antenna radiating layer, such as Figure 6 As shown, the antenna includes a fifth dielectric substrate, a square ring metal patch, and a microstrip patch antenna. The fifth dielectric substrate is made of RO4350B with a dielectric constant of 3.66 and a thickness of 0.508 mm. The microstrip patch antenna is a 2×2 array, with each antenna element consisting of a square metal patch with a side length of 8.6 mm. The element period is 15 mm × 15 mm, and the element spacing is 45 mm. Two-dimensional periodically arranged square ring metal patches are arranged around the antenna elements. The square ring metal patches have a period of 7.5 mm × 7.5 mm, an outer ring side length of 6.5 mm, and an inner ring hole with a side length of 3.2 mm at its center. The square ring metal patches and the square metal patches are used to provide the lower layer reflection phase required by the FP resonant cavity.

[0055] The antenna feed layer, such as Figure 7 and Figure 8As shown, it includes a sixth dielectric substrate, a slotted metal ground, and a 1-to-4 microstrip power divider; the sixth dielectric substrate is made of RO4350B with a dielectric constant of 3.66 and a thickness of 0.508mm; the slotted metal ground is used to provide RF ground for the feed and to longitudinally couple the electromagnetic wave energy of the lower feed line to the upper microstrip patch antenna for radiation; the slots on the slotted metal ground are all located directly below each microstrip patch antenna, and the length and width of the slots are 3.5mm and 1mm, respectively.

[0056] The one-to-four microband power divider, such as Figure 9 As shown, the system consists of three cascaded T-type 1-to-2 microstrip power dividers to achieve equal power distribution of the feed energy. Each T-type 1-to-2 microstrip power divider includes a 50Ω microstrip transmission line and a 1 / 4 wavelength microstrip impedance matching device. The 50Ω microstrip transmission line has a linewidth of 1.5mm and a 1.1mm chamfer at its right-angle bends. The 1 / 4 wavelength microstrip impedance matching device has a linewidth of 0.72mm and a line length of 6.6mm, with a 0.6mm chamfer at its right-angle bends. The 50Ω feed line at the end of the 1-to-4 microstrip power divider extends horizontally beyond the outer edge of the slot by 1.5mm to achieve impedance matching.

[0057] See Figure 10 The figure shows the simulation results of the radiation performance of the FP resonant cavity antenna in this embodiment. It can be seen that the normal gain of the FP resonant cavity antenna reaches 20.96 dBi in the two typical directions of E-plane and H-plane, and the sidelobe level is low, realizing the characteristics of a high-gain transmission array antenna.

[0058] See Figure 11This document presents the simulation results of three liquid crystal dielectric constant states and their corresponding S21 transmission amplitude and transmission phase during the phase compensation and control process of the liquid crystal transmission array in this embodiment. At the 10GHz center frequency, three phase quantization states, ε = 2.43, ε = 2.81, and ε = 3.16, were selected for liquid crystal phase control. The S21 transmission amplitude corresponding to ε = 2.43 and ε = 3.16 is -6.51dB, and the S21 transmission amplitude corresponding to ε = 2.81 is -3.94dB. In terms of transmission phase, the phase difference between ε = 3.16 and ε = 2.81 is 120°, and the phase difference between ε = 2.81 and ε = 2.43 is 121°. Therefore, based on the phase compensation calculation results, the liquid crystal dielectric constant value corresponding to the 0°~120° phase compensation range can be uniformly quantized and adjusted to ε = 3.16, the liquid crystal dielectric constant value corresponding to the 120°~240° phase compensation range can be uniformly quantized and adjusted to ε = 2.81, and the liquid crystal dielectric constant value corresponding to the 240°~360° phase compensation range can be uniformly quantized and adjusted to ε = 2.43, thereby finally realizing the liquid crystal phase compensation control of the transmission array antenna.

[0059] See Figure 12 The figure shows the simulation results of the overall S11 return loss of the antenna in this embodiment. It can be seen that the S11 return loss at the 10GHz center frequency point reaches 18.6dB, and the energy loss caused by the antenna due to reflection is relatively small.

[0060] See Figures 13 to 18 The diagram shows the phase compensation of the one-dimensional beam scanning and the gain simulation results when the antenna operates at 10 GHz in this embodiment, with the antenna pointing at -45°, -30°, -15°, 15°, 30° and 45° respectively. It can be seen that the antenna has good directivity in one-dimensional beam scanning, and precise beam pointing control of more than 12.37 dBi is achieved in the range of -45° to 45° by liquid crystal phase dielectric modulation.

Claims

1. A transmissive liquid crystal phased array antenna based on an FP resonant cavity, characterized in that, Operating in the X-band, it comprises, from top to bottom, a liquid crystal transmission array layer, a first air layer, a partially reflective surface layer, a second air layer, an antenna radiating layer, and an antenna feed layer; The liquid crystal transmission array layer is composed of a two-dimensional periodic arrangement of multiple frequency selective surface (M-FSS) transmission units; a single transmission unit includes a first dielectric substrate, a first patch-type FSS unit, a first liquid crystal layer, a first slit-type FSS unit, a second dielectric substrate, a second slit-type FSS unit, a second liquid crystal layer, a second patch-type FSS unit, and a third dielectric substrate stacked from top to bottom. Both the first surface-mount FSS unit and the second surface-mount FSS unit are provided with a DC microstrip bias line running through the center of the surface-mount unit. The DC microstrip bias lines in the same column are interconnected to apply a bias voltage to all surface-mount FSS units in the same column simultaneously. The first slit FSS unit and the second slit FSS unit cooperate with the surface-mount FSS units on the same side to clamp the liquid crystal layer, forming a double-layer liquid crystal phase-shifting structure. By applying differentiated bias voltages to each column of surface-mount FSS units, the equivalent dielectric constant of the liquid crystal layer in the corresponding region is adjusted, thereby achieving electromagnetic wave transmission phase compensation. The partially reflective surface layer includes a fourth dielectric substrate and a plurality of first metal patch units arranged in a two-dimensional periodic pattern on its upper surface; the partially reflective surface layer serves as the upper reflective interface of the FP resonant cavity, providing the upper cavity reflection phase required for the coherent superposition of electromagnetic waves. The antenna radiating layer includes a fifth dielectric substrate, a microstrip patch radiating unit array disposed on the upper surface of the fifth dielectric substrate, and a second metal patch unit periodically arranged around each radiating unit; the microstrip patch radiating unit array and the second metal patch unit together constitute the lower phase reflection interface of the FP resonant cavity, providing the lower cavity reflection phase required for the coherent superposition of electromagnetic waves. The antenna feed layer includes a sixth dielectric substrate. The lower surface of the sixth dielectric substrate is provided with a one-to-many microstrip power divider, and the upper surface is provided with a slotted metal ground. The one-to-many microstrip power divider is composed of multiple T-type one-to-two microstrip power dividers cascaded together to achieve equal power distribution of the feed energy. The slotted metal ground has rectangular coupling slots that are directly opposite each microstrip patch radiating element to longitudinally couple and transmit electromagnetic wave energy to the radiating elements above.

2. The transmissive liquid crystal phased array antenna based on an FP resonant cavity as described in claim 1, characterized in that, Both the first and second surface-mount FSS units adopt a 45° rotated Jerusalem cross-shaped metal surface-mount configuration; Both the first and second slotted FSS units have Jerusalem cross-shaped perforated slots.

3. The transmissive liquid crystal phased array antenna based on an FP resonant cavity as described in claim 2, characterized in that, The microstrip patch radiating unit array includes four identical and uniformly distributed square patch radiating units; the one-to-many microstrip power divider is a one-to-four microstrip power divider.

4. The transmissive liquid crystal phased array antenna based on an FP resonant cavity as described in claim 3, characterized in that, In the aforementioned one-to-four microstrip power divider, the right-angle bends of the microstrip lines are chamfered.

5. A transmissive liquid crystal phased array antenna based on an FP resonant cavity as described in any one of claims 2-4, characterized in that, The first metal patch unit is a square metal patch, a square-ring metal patch, a circular metal patch, or a ring-shaped metal patch.

6. A transmissive liquid crystal phased array antenna based on an FP resonant cavity as described in any one of claims 2-4, characterized in that, The second metal patch unit is a square metal patch, a square ring-shaped metal patch, a circular metal patch, or a ring-shaped metal patch.

7. A transmissive liquid crystal phased array antenna based on an FP resonant cavity as described in any one of claims 2-4, characterized in that, The thickness of the first liquid crystal layer and the second liquid crystal layer ranges from 0.254 mm to 0.508 mm.

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