Dual-polarized liquid crystal phased array based on dual-polarized radiation subarray and liquid crystal phase shifter

Abstract

The invention discloses a dual-polarized liquid crystal phased array based on a dual-polarized radiation subarray and a liquid crystal phase shifter. The dual-polarized liquid crystal phased array comprises the dual-polarized radiation subarray, the liquid crystal phase shifter and a power divider. The dual-polarized radiation subarray is obtained by cascading a plurality of dual-polarized radiation units in a series-fed manner, and the tapered output characteristic of a series-fed network enables a directional diagram to have a low side lobe characteristic in the longitudinal direction. And the dual-polarized radiation sub-arrays are in shunt-feed connection through a power divider. The liquid crystal phase shifter serves as a core device, continuous adjustment of a transmission phase can be achieved by adjusting bias voltage, the two ends of the liquid crystal phase shifter are connected with the radiation subarray and the power distribution circuit respectively in a slot coupling mode, and all the phase shifters are hidden below the array and do not occupy extra space. According to actual measurement, the dual-polarization channel of the liquid crystal phased array has return loss of more than 10 dB and port isolation of more than 25 dB in a designed frequency band, beam scanning is realized within + / -40 degrees, and the dual-polarization channel has an important application prospect in the fields of future communication and the like.

Description

Technical Field

[0001] This invention relates to the field of dual-polarized liquid crystal phased array technology, and particularly to a dual-polarized liquid crystal phased array based on a dual-polarized radiating subarray and a liquid crystal phase shifter. Background Technology

[0002] With the rapid development of 5G technology, the demand for low-cost, large-scale phased array antennas is becoming increasingly prominent in the communications field. Traditional active phased array antennas rely on silicon-based phased array chips to independently control the amplitude and phase of the antenna elements during beam scanning. As operating frequencies increase and array sizes grow, the number of chips required for the array increases, and the complexity of the control circuitry also rises. Therefore, millimeter-wave phased arrays face challenges such as high economic costs and complex system design. Compared to phased arrays with single-line polarization radiation characteristics, dual-polarized antennas are widely used in wireless communication systems due to their advantages such as improved communication channel capacity and reduced signal fading. At the same time, dual-polarized phased arrays impose high isolation and miniaturization requirements on antenna element design, and also require dual-feed networks and compact array arrangements.

[0003] Liquid crystals, as electrically tunable anisotropic materials, have been widely used in optoelectronic devices, display panels, and microwave devices in recent years. Liquid crystal phase shifters are designed based on the physical property that liquid crystal molecules exhibit different dielectric constants under different bias voltages. By changing the bias voltage, the transmission phase of the phase shifter can be dynamically controlled, and this phase has the characteristics of a wide operating frequency band and continuous phase change. Large-scale multi-channel liquid crystal phased arrays based on liquid crystal phase shifters can be fabricated using the same processes as liquid crystal display panels, resulting in lower costs and mature control system solutions. With advancements in high-performance electromagnetic liquid crystal materials and the maturity of processing technology, liquid crystal phased array antenna technology has gradually become a new solution for low-cost, low-power phased array antenna design.

[0004] Conventional liquid crystal phased arrays utilize a double-layer glass substrate architecture, employing molten quartz glass as the upper and lower substrates encapsulated within a cell filled with anisotropic liquid crystal material. Patent (CN118431749A) proposes a design method for linearly polarized liquid crystal phased arrays based on this stacked structure. The liquid crystal phase shifter uses an inverted microstrip line structure, while the radiating element employs a patch antenna structure. This design provides a 1×8 scale implementation and achieves beam scanning from 0° to 40°. Patent (CN11758676A) achieves a high-gain liquid crystal phased array design method at the same array size by replacing the patch antenna with a Yagi antenna. However, limited by end-fire radiation characteristics, this design can only achieve one-dimensional array arrangements, providing a 1×4 scale array as an example. The patent (CN117276880A) extends the structure into a dual-polarization channel. By changing the phase difference between the channels, a radiatively polarized reconfigurable liquid crystal phased array unit can be realized. However, the patent does not explicitly provide a method for extending the dual-polarization unit to an array.

[0005] Besides this traditional stacked structure, the dual-substrate structure can be extended to multi-substrate structures with multiple layers of glass. The phased array unit proposed in patent (CN114006167A) employs a four-layer glass architecture, increasing the antenna design freedom and enabling a wide-bandwidth scanning angle metasurface antenna structure. The phase shifter uses an improved inverted microstrip line structure. Simulation results show that the array can achieve a scanning performance of ±60° from 13.2 to 16 GHz. However, limited by the compact space and high-loss glass substrate, this design also lacks the prospect of being extended to dual-polarized arrays.

[0006] Furthermore, a non-glass dielectric substrate can be added to the outer side of the glass. This multilayered structure, combining a glass substrate and a printed circuit board, provides greater freedom in the design of the antenna radiating element. Patent (CN114006167A) employs such a multilayered architecture, where the linear polarization unit and coupling gaps can be etched onto the outer dielectric substrate, and a differential phase shifter is used. This design only provides a 2×2 array arrangement and does not provide a corresponding feed network. Patent (CN117321855A) further optimizes the unit structure based on this type of multilayered structure, improving it into a circularly polarized radiating unit, and provides a parallel feed network and a 1×16 liquid crystal phased array example. However, this design has low aperture utilization, only achieving a linear array arrangement. In addition, such a multilayered structure gives the unit structure design diversity and freedom, providing the possibility of dual-polarization unit design. Summary of the Invention

[0007] This invention provides a dual-polarized liquid crystal phased array based on a dual-polarized radiating subarray and a liquid crystal phase shifter. By employing a stacked structure of glass substrate and printed circuit board hybrid pressing, a dual-polarized antenna element and a corresponding dual-polarized liquid crystal phased array are designed, thereby solving the problem that single-polarized liquid crystal phased arrays based on glass panels are difficult to expand into dual-polarized arrays. By using a dual-polarized radiating subarray instead of a single antenna element as the radiating element of the liquid crystal phased array, the shortcomings of low beam gain and low aperture utilization caused by the large size of the liquid crystal phase shifter and the small size of the antenna element in traditional liquid crystal phased arrays are solved.

[0008] This invention provides a dual-polarized liquid crystal phased array based on a dual-polarized radiating subarray and a liquid crystal phase shifter. The dual-polarized liquid crystal phased array consists of three parts: a dual-polarized radiating subarray, a liquid crystal phase shifter, and a parallel-feed power divider. The dual-polarized radiating subarray comprises M dual-polarized radiating elements and two 1-to-8 series-fed power dividers. The M dual-polarized radiating elements are connected by cascaded series-fed power dividers, and the output ports of the series-fed power dividers are connected to the input ports of the dual-polarized radiating elements. In the longitudinal arrangement direction, each dual-polarized radiating subarray is connected to two liquid crystal phase shifters through slot coupling. In the transverse arrangement direction, N dual-polarized radiating subarrays are arranged periodically, and each dual-polarized radiating subarray is connected to two parallel-fed power dividers, resulting in a dual-polarized liquid crystal phased array with M×N elements. Where M is the number of bipolarized radiating elements in the bipolarized radiating subarray, N is the number of bipolarized radiating subarrays, M is an even number and M is greater than or equal to 2, and the spacing between the bipolarized radiating elements is 0.3λ. g up to 0.7λ g , where λ g The center frequency wavelength.

[0009] Optionally, in one embodiment of the present invention, in the stacked structure, the dual-polarized liquid crystal phased array is manufactured by a mixed pressing of printed circuit boards and glass substrates, with the printed circuit boards and glass substrates fabricated in steps and then pressed together to form the final dual-polarized liquid crystal phased array; the printed circuit board portion includes 5 dielectric substrate layers and 4 adhesive layers, with a total of 8 copper layers; the glass substrate includes 2 layers of glass, filled with low-cell-thickness liquid crystal, and the inner surfaces of the 2 glass layers are covered with metal; the glass substrate and the adhesive layers are bonded together with a layer of adhesive; the dual-polarized radiating subarray and the parallel-feed power divider of the dual-polarized liquid crystal phased array are implemented on the printed circuit board structure, and the liquid crystal phase shifter portion is implemented on the glass substrate portion.

[0010] Optionally, in one embodiment of the present invention, the dual-polarized radiating unit comprises three dielectric substrates and two adhesive layers, with a total of five copper layers. In terms of the radiating structure, the dual-polarized radiating unit adopts a stacked patch structure, with the two patches located on the upper and lower surfaces of the top dielectric substrate, respectively. In terms of the feeding structure, a feed stripline slot coupling feed is used, with the top and bottom metal grounds of the stripline located on the upper and lower surfaces of the middle dielectric substrate, respectively, and the inner conductor of the stripline located on the lower surface of the middle dielectric substrate. Two "I"-shaped slots are formed on the top metal ground directly below the projection of the stacked patch for slot coupling feed. Between the top and bottom metal grounds, several metal pillars are also formed around the antenna element and the edge of the slots to construct an isolation cavity, which improves the isolation between the two polarizations. The ends of the two feed striplines are connected to two coaxial probes extending downwards for connection with a series feed power divider.

[0011] Optionally, in one embodiment of the present invention, the series-fed power divider includes two dielectric substrates and one adhesive layer, with a total of three copper layers. The series-fed power divider adopts a stripline structure, with the top metal ground and the bottom metal ground located on the upper surface of the upper dielectric substrate and the lower surface of the lower dielectric substrate, respectively, and the inner conductor of the stripline located on the upper surface of the lower dielectric substrate. Several metal pillars are placed between the two metal ground layers to suppress unwanted parallel plate modes and improve the purity of the stripline mode. The series-fed power divider consists of several matching stubs, several impedance transformation stubs, one coupling slot, and M-1 1-to-2 T-shaped stubs. The series-fed power divider includes one output terminal and is coupled to the liquid crystal phase shifter through a slot. The series-fed power divider includes M output terminals, which are respectively connected to the coaxial probes of M dual-polarization units.

[0012] Optionally, in one embodiment of the present invention, the parallel-feed power divider and the series-feed power divider adopt the same stacked structure, including N output ports; the parallel-feed power divider consists of matching stubs, coupling slots, and N-1 parallel T-shaped stubs of 1 to 2; an isolation cavity is constructed between the upper and lower metal ground planes by through holes; the parallel-feed power divider includes one input terminal connected to an external RF input port; the parallel-feed power divider includes N output terminals, which are respectively coupled to N liquid crystal phase shifters through slots.

[0013] Optionally, in one embodiment of the present invention, the stacked structure of the liquid crystal phase shifter consists of an upper glass layer, liquid crystal, and a lower glass layer, with a metal layer covering the inner side of the glass. The transmission-type liquid crystal phase shifter is constructed based on the metal layer structure, specifically comprising a balun structure, a parallel differential double-line structure, and a capacitive metal strip vertically loaded below the double lines. The loaded capacitive metal strip and the differential double lines overlap in the vertical orthographic projection, introducing a variable capacitor to generate an adjustable phase shift. A phase-shifting unit is constructed by loading a capacitive metal strip below the double lines, and several phase-shifting units together constitute a phase-shifting segment. All capacitive metal strips are connected to the lower bias line, and the differential double-line structure is connected to the upper bias line. A bias voltage is applied between the upper and lower bias lines to deflect the liquid crystal molecules, thereby achieving complete 360° periodic control of the transmission phase.

[0014] The dual-polarized liquid crystal phased array based on a dual-polarized radiating subarray and a liquid crystal phase shifter, according to embodiments of the present invention, has the following beneficial effects: 1) It features dual-polarization radiation characteristics. A stacked rectangular patch is used as the radiation unit, and orthogonally arranged slots are used for stripline coupling feeding. By introducing metal vias around the feed line to construct a cavity, the isolation between the two feed ports is improved, achieving a high-purity dual-polarization radiation unit. 2) It has broadband characteristics. Stacked rectangular patches are used as radiating elements to extend the antenna impedance bandwidth. A multi-stage cascaded matching structure is used to realize a broadband power divider for parallel and series connection. A differentially loaded microstrip line with gradient matching and a broadband balun structure are used to realize a broadband liquid crystal phase shifter. Finally, the various modules are cascaded to obtain a broadband liquid crystal phased array. 3) It has a high aperture utilization rate. In the longitudinal arrangement of the array, each radiation channel contains two liquid crystal phase shifters and a series-fed dual-polarized subarray. By connecting the phase shifters to the subarray instead of individual radiation elements, the utilization rate of the array surface and the radiation gain of a single channel can be improved, further increasing the array gain; 4) Scalability. In the horizontal array arrangement, the structure of each radiation channel is identical, allowing for expansion to multiple radiation channels through periodic arrangement. After increasing the number of channels, only the parallel feed network needs to be redesigned; the radiation structure itself does not need to be redesigned. Furthermore, all phase shifters are concealed beneath the array, occupying no additional space. 5) Low sidelobe characteristics. In the longitudinal arrangement of the array, the output amplitude distribution of the series feed network is designed as a tapered distribution descending from the center to both ends, thus giving the subarray low sidelobe characteristics; in the transverse arrangement of the array, the output characteristics of the parallel feed network can also be designed to have a tapered distribution. Furthermore, the proportion of the tapered distribution can be modified by adjusting the parameters of the impedance transformation stubs of the feed network. 6) Fast response time. Since the liquid crystal response time is proportional to the square of the liquid crystal thickness, this design uses a 5-micron low-cell-thickness liquid crystal layer to enable the liquid crystal material to have a fast liquid crystal response time, thereby reducing the beam switching time of the liquid crystal phased array antenna.

[0015] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0016] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a three-dimensional schematic diagram of a dual-polarized liquid crystal phased array based on a dual-polarized radiating subarray and a liquid crystal phase shifter, according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the stacked structure of a dual-polarization liquid crystal phased array according to an embodiment of the present invention; Figure 3 This is a top view of a dual-polarized radiating unit according to an embodiment of the present invention; Figure 4 This is a top view of a series-type power supply network according to an embodiment of the present invention; Figure 5 This is a top view of a dual-polarized radiating subarray according to an embodiment of the present invention; Figure 6 This is a top view of a parallel power supply network according to an embodiment of the present invention; Figure 7 This is a top view of a liquid crystal phase shifter according to an embodiment of the present invention; Figure 8 The simulation and measured scattering coefficients of the dual-polarized liquid crystal phased array according to an embodiment of the present invention; Figure 9 The simulation and measured gain of the dual-polarized liquid crystal phased array in this embodiment of the invention are shown in (a) for P1 port excitation and (b) for P2 port excitation. Figure 10 The scanning pattern of the simulation of the 29GHz dual-polarized liquid crystal phased array according to an embodiment of the present invention is shown in (a) for P1 port excitation and (b) for P2 port excitation. Figure 11 The above are the measured scanning patterns of the 29GHz dual-polarized liquid crystal phased array according to an embodiment of the present invention. (a) is the P1 port excitation, and (b) is the P2 port excitation. Figure 12 (a) and (b) are schematic diagrams of different structures and shapes of laminated patches according to embodiments of the present invention. Detailed Implementation

[0017] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0018] like Figure 1 As shown, the dual-polarization liquid crystal phased array consists of three parts: a dual-polarization radiating subarray, a liquid crystal phase shifter, and a parallel-feed power divider. The dual-polarized radiating subarray comprises M dual-polarized radiating elements and two 1-to-8 series-fed power dividers. The M dual-polarized radiating elements are connected by cascaded series-fed power dividers, with the output ports of the series-fed power dividers connected to the input ports of the dual-polarized radiating elements. The N elements are connected by two cascaded series-fed power dividers. In the vertical arrangement direction, each dual-polarized radiating subarray and two liquid crystal phase shifters are connected through slot coupling. In the horizontal arrangement direction, the N dual-polarized radiating subarrays are arranged periodically, and each dual-polarized radiating subarray is connected to two parallel-fed power dividers, resulting in a dual-polarized liquid crystal phased array with M×N elements. Where M is the number of bipolarized radiating elements in the bipolarized radiating subarray, N is the number of bipolarized radiating subarrays, M is an even number and M is greater than or equal to 2, and the spacing between the bipolarized radiating elements is 0.3λ. g up to 0.7λ g , where λ g The center frequency wavelength.

[0019] A single dual-polarization subarray comprises M dual-polarization elements and two 1-to-M series-fed power dividers. Internally, the M dual-polarization elements have M horizontal polarization input ports and M vertical polarization input ports, which are connected to the 2M output ports of the two series-fed power dividers. Overall, a single subarray contains two input ports, corresponding to the horizontal and vertical polarization radiation of the entire subarray, respectively.

[0020] In embodiments of the present invention, the dual-polarization liquid crystal phased array is fabricated using a mixed-pressing process involving printed circuit boards and glass substrates. Specifically, the printed circuit board and glass substrate are fabricated in stages and then pressed together to form the final dual-polarization liquid crystal phased array. The printed circuit board portion comprises 5 dielectric substrate layers and 4 adhesive layers, with a total of 8 copper layers. The glass substrate comprises 2 layers of glass, internally filled with low-cell-thickness liquid crystal, and the inner surfaces of the 2 glass layers are covered with a metal layer. A single layer of adhesive bonds the glass substrate and the adhesive layers. The dual-polarization radiating subarray and parallel-feed power divider of the dual-polarization liquid crystal phased array are implemented on the printed circuit board structure. The liquid crystal phase shifter portion of the dual-polarization liquid crystal phased array is implemented on the glass substrate portion.

[0021] In an embodiment of the invention, the dual-polarized radiating element comprises three dielectric substrate layers and two adhesive layers, with a total of five copper layers. In terms of the radiating structure, the radiating element adopts a stacked patch structure, with the two patches located on the upper and lower surfaces of the top dielectric substrate, respectively. In terms of the feeding structure, a stripline slot coupling feed is used, with the top and bottom metal grounds of the stripline located on the upper and lower surfaces of the middle dielectric substrate, respectively, and the inner conductor of the stripline located on the lower surface of the middle dielectric substrate. Two "I"-shaped slots are formed on the top metal ground directly below the projection of the stacked patch for slot coupling feed. Between the top and bottom metal grounds, several metal pillars are formed around the antenna element and the edge of the slots to construct an isolation cavity, improving the isolation between the two polarizations. The ends of the two striplines are connected to two coaxial probes extending downwards for connection to a series-feed power divider.

[0022] The top and bottom metal ground layers in the aforementioned dual-polarized radiating unit are metal layers, specifically the copper layers in the phrase "a total of 5 copper layers are laid," see [link to relevant documentation]. Figure 2 Instructions 4-12 and 4-13 are provided. Metal patterns can be etched on both sides of the dielectric substrate, so the copper layer is generally on the upper or lower surface of the substrate; however, copper is not necessarily present on both the upper and lower surfaces. The term "metal ground" mentioned in this article simply indicates that the electrical property of this copper layer is "ground." "Surface mount," "metal ground," and "power supply network" are all different descriptions of electrical properties, but they are all essentially copper.

[0023] In an embodiment of the present invention, the series-fed power divider comprises two dielectric substrates and one adhesive layer, with a total of three copper layers. The series-fed power divider employs a stripline structure, with the top and bottom metal ground layers located on the upper and lower surfaces of the upper and lower dielectric substrates, respectively. The inner conductor of the stripline is located on the upper surface of the lower dielectric substrate. Several metal pillars are placed between the two metal ground layers to suppress unwanted parallel plate modes and improve the purity of the stripline mode. The series-fed power divider consists of several matching stubs, several impedance transformation stubs, one coupling slot, and M-1 1-to-2 T-shaped stubs. The series-fed power divider includes one output terminal coupled to the liquid crystal phase shifter via a slot; the series-fed power divider also includes M output terminals, each connected to a coaxial probe of one of the M dual-polarization units.

[0024] In embodiments of the present invention, the parallel-feed power divider and the series-feed power divider adopt the same stacked structure, containing N output ports. The parallel-feed power divider consists of matching stubs, coupling slots, and N-1 parallel T-shaped stubs with a 1-to-2 split. Similarly, an isolation cavity is constructed between the upper and lower floor planar sections using through holes. The parallel-feed power divider includes one input terminal connected to an external RF input port; the parallel-feed power divider includes N output terminals, each coupled to one of the N liquid crystal phase shifters via slots.

[0025] In an embodiment of the present invention, N is the number of dual-polarization subarrays. Each subarray contains two input ports, corresponding to horizontal and vertical polarization radiation, respectively. Each polarization port of a single subarray is connected to a liquid crystal phase shifter. N subarrays connect to 2N phase shifters, with the vertical polarization port and the horizontal polarization port each connected to N liquid crystal phase shifters.

[0026] In embodiments of the present invention, the stacked structure of the liquid crystal phase shifter consists of an upper glass layer, liquid crystal, a lower glass layer, and a metal layer covering the inner side of the glass. The transmission-type liquid crystal phase shifter is constructed based on the metal layer structure, specifically comprising a balun structure, a parallel differential biline structure, and a capacitive metal strip vertically loaded below the biline. The loaded capacitive metal strip and the differential biline overlap in the vertical orthographic projection, thereby introducing a variable capacitance to generate an adjustable phase shift. A phase-shifting unit is constructed by loading a capacitive metal strip below the biline, and several phase-shifting units together constitute a phase-shifting segment. All capacitive metal strips are connected to the lower bias line, and the differential biline structure is connected to the upper bias line. A bias voltage is applied between the upper and lower bias lines to deflect the liquid crystal molecules, thereby achieving complete 360° periodic control of the transmission phase.

[0027] The dual-polarized liquid crystal phased array topology proposed in this invention is based on a dual-polarized radiating subarray and a transmission liquid crystal phase shifter. In this topology, the phase shifter in a single radiating channel is connected to a series-feed subarray instead of a single antenna element, thereby improving aperture utilization and reducing sidelobe level.

[0028] The present invention proposes a method for realizing a dual-polarization liquid crystal phased array, namely, a design method that uses PCB technology to design the dual-polarization subarray and glass substrate technology to design the liquid crystal phase shifter part and then bonding them together.

[0029] The proposed stacked structure and coupling dimensions of the liquid crystal phase shifter to the dual-polarized radiating subarray in this invention achieve hole-free signal transmission through non-contact coupling technology.

[0030] The following detailed description of the present invention, based on a dual-polarized radiating subarray and a liquid crystal phase shifter, is provided in conjunction with the accompanying drawings and specific embodiments.

[0031] This invention proposes a design scheme for a dual-polarization liquid crystal phased array operating at 27-31 GHz. The phased array comprises three parts: a dual-polarization radiating subarray 1, a liquid crystal phase shifter 2, and a parallel-feed power divider 3. The dual-polarization radiating subarray 1 includes 8 (M=8) dual-polarization radiating elements 4 and two 1-to-8 series-feed power dividers 5. The output ports of the latter are connected to the input ports of the former, and cascading them yields a dual-polarization radiating subarray with two input ports. Combining parts 1, 2, and 3 yields the final array, which has a size of 8×8 (M×N) and contains 8 (N=8) dual-polarization subarrays. In the specific assembly steps, the arrangement is first carried out vertically, with each dual-polarized radiating subarray 1 and two liquid crystal phase shifters 2 connected by slot coupling; then, the arrangement is carried out horizontally, with the eight dual-polarized radiating subarrays arranged periodically and connected to two parallel-feed power dividers 3 respectively, resulting in a dual-polarized liquid crystal phased array with a total of 8×8 units. For a detailed structural breakdown, see [link to structural details]. Figure 1 As shown.

[0032] The array unit size of a dual-polarization liquid crystal phased array is d=5.5mm, which is typically used when the spacing between the dual-polarization units is 0.35λ. g up to 0.7λ g , where λ g The center frequency wavelength is given. The overall dimensions of the array are Dx × Dy = 85.9 mm × 85.9 mm. The longitudinal dimension Dy is typically M × d + 2 × Df1, where Df = 20.95 mm, which is the longitudinal dimension of the parallel feeder network. The value of Df ranges from 0.25 × (log2(N) + 1) × λ. g up to 0.75×(log2(N)+1)×λ g The lateral dimension Dx is N×d+2×Dlc, where Dlc=20.95mm is the lateral extension width of the reserved control line, and the value of Df ranges from 10mm to 30mm.

[0033] In terms of the stacked structure, the liquid crystal phased array is manufactured using a mixed-pressing method involving printed circuit boards and glass substrates. Specifically, the printed circuit boards 6 and the glass substrates are fabricated in steps, and then pressed together to form the final liquid crystal phased array. Figure 1 and Figure 2 As shown. Specifically, the printed circuit board portion comprises 5 dielectric substrate layers (6-1 / 3 / 5 / 7 / 9) and 4 adhesive layers (6-2 / 4 / 6 / 8), numbered from 6-1 to 6-9 from top to bottom. The glass substrate comprises 2 layers of glass, internally filled with low-cell-thickness liquid crystal, and the inner surfaces of the 2 glass layers are covered with a metal layer. The dual-polarized radiating subarray 1 and the parallel-fed power divider 3 are etched as metal structures on the multilayer printed circuit board 6, and a total of 16 liquid crystal phase shifters are distributed on the glass substrate.

[0034] The side and top views of the dual-polarized radiating unit 4 are shown in Figures 2 and 3. Figure 3 Specifically, the unit includes an upper radiating patch 4-1, a lower radiating patch 4-2, and coupling slots 4-3 and 4-4 corresponding to dual-polarization excitation, feeding striplines 4-5 and 4-6, feeding probes 4-7 and 4-8, and feeding coaxial slots 4-9 and 4-10. In addition, the radiating subarray also includes an isolation cavity 4-11 for improving isolation, an upper metal ground plane 4-12, and a lower metal plate 4-13. The two coupling slots of the upper metal ground plane are both I-shaped slots, but can also be straight or other shapes. The two coaxial slots of the lower metal ground plane are both circular slots, but can also be hexagonal or other shapes. The unit works by exciting two orthogonal operating modes of the patches through striplines to achieve dual-polarization operation. The upper patch has a size of 2.7mm × 2.7mm, and the lower patch has a size of 2.12mm × 2.12mm, typically with a value of 0.15λ. g up to 0.25λ g and 0.22λ g up to 0.32λ g .

[0035] The side and top views of the series-fed power divider 5 are shown in the figure. Figure 2 and Figure 4 The series-fed power divider uses a stripline as the waveguide structure and contains M output ports. The series-fed power divider 5 consists of a matching stub 5-1, an impedance transformation stub 5-2, a coupling slot 5-3, and a multi-stage 1-to-2 T-shaped stub, with a total of 7 (M-1) T-shaped stubs. The T-shaped stubs consist of an output stub 5-4 and an impedance transformation stub 5-2. In addition, it includes an isolation cavity 5-5, a top metal ground plane 5-6, and a bottom metal ground plane 5-7. The isolation cavity suppresses unwanted parallel plate modes to ensure the purity of the stripline mode within the operating frequency band. The series-fed power divider includes one output terminal and is coupled to the liquid crystal phase shifter via a slot. The matching stub 5-1 is introduced to improve impedance matching. The series-fed power divider includes eight output terminals, which are connected to the coaxial probes 4-7 / 4-8 of the eight dual-polarization units 4, respectively. A schematic diagram of the dual-polarization subarray obtained by cascading the series-fed power divider 5 and the dual-polarization units 4 is shown below. Figure 5 As shown.

[0036] The side and top views of the parallel feed power divider 3 are shown in the figure. Figure 2 and Figure 6The parallel-feed power divider and the series-feed power divider adopt the same stacked structure and are located on the same layer. The parallel-feed power divider contains 8 (N=8) output ports. The parallel-feed power divider 3 consists of a matching stub 3-1, a coupling slot 3-2, and a multi-stage 1-to-2 T-shaped stub, with a total of 7 (N-1) T-shaped stubs. The T-shaped stubs consist of an output stub 3-3 and an impedance transformation stub 3-4. In addition, it also includes an isolation cavity 3-5, an upper metal ground plane 3-6, and a lower metal ground plane 3-7. The parallel-feed power divider has one input terminal, which transforms the stripline to the coplanar waveguide structure 3-7 through a blind via 3-6 and connects to the external RF connector 7; the parallel-feed power divider has 8 output terminals, which are respectively coupled to 8 liquid crystal phase shifters through slots.

[0037] like Figure 7 As shown, the stacked structure of the liquid crystal phase shifter 2 consists of an upper glass layer 2-1, a lower glass layer 2-2, and liquid crystal 2-3 filling the space between the two glass layers. The input terminal 2-4 and output terminal 2-5 of the phase shifter are both microstrip line single-wire structures, coupled to the parallel feed network 2 and the series feed network 3 respectively via coupling gaps 3-2 and 5-3. At the gap coupling points, matching stubs 2-10 and 2-11 are also connected to the input and output terminals of the phase shifter to improve impedance matching. The single-wire structure of the microstrip line is transformed into a parallel differential double-wire structure 2-7 after passing through a balun structure 2-6. The differential double-wire structure and the capacitive metal strip 2-8 loaded perpendicular to the double-wire direction together constitute a phase-shifting unit, and several phase-shifting units together constitute a phase-shifting segment. The loaded capacitive metal strip and the differential double-wire overlap in the vertical orthographic projection, thereby introducing a variable capacitor to generate an adjustable phase shift. In the specific operation of changing the liquid crystal material parameters, all capacitive metal strips are connected by a lower bias line made of indium tin oxide (ITO). A differential dual-line structure is also connected by an upper bias line. A bias voltage is applied between the differential bias lines to achieve liquid crystal molecule deflection and phase shifter control. The phase-shifting segment is then coupled back to a single-line structure via a balun for power feeding. The liquid crystal phase shifter 2 and the multilayer printed circuit board 6 are connected by adhesive layers 2-9.

[0038] Figure 8 Frequency response curves of the measured and simulated scattering parameters of the liquid crystal phased array are presented. The simulated and measured reflection coefficients and coupling coefficients show good agreement. Specifically, the one-port reflection coefficient... S 11 |Impedance bandwidth less than -10dB is 26-31.97 GHz, two-port reflection coefficient| S 22 The impedance bandwidth (less than -10dB) is 26-31.64 GHz, and the combined dual-polarization bandwidth is 26-31.64 GHz. Coupling coefficient between one-port and two-port terminals. S 21The voltage level is less than 28 dB. Actual test results demonstrate that this dual-polarization liquid crystal phased array has good broadband matching characteristics and good port isolation between the two polarization input ports.

[0039] Figure 9 Frequency response curves of the measured and simulated gains of the liquid crystal phased array are presented. It can be seen that when generating a normal beam within the design frequency band, the simulated and measured maximum gains for one-port excitation are 17.57 dBi and 15.94 dBi, respectively, while the simulated and measured maximum gains for two-port excitation are 17.35 dBi and 17.23 dBi, respectively. The cross-polarization voltages for both-port excitation are both below -15 dB.

[0040] Figure 10 and Figure 11 Simulated and measured beam scanning patterns of the liquid crystal phased array at 29 GHz are presented. The measured results show that, under one-port and two-port excitation, the antenna can achieve a beam pointing error of less than 1° within a scanning angle of ±40°, a beam scanning gain drop of <3dB, a maximum sidelobe of > -8dB, cross-polarization of less than -15dB, high polarization purity, and good beam symmetry.

[0041] In embodiments of the present invention, the alternative to the radiating element currently employs a dual-polarized antenna array constructed from square stacked patch elements. The antenna structure can be modified, replacing it with a single-layer patch or multiple stacked patches, or with asymmetric patch antennas of different planar geometries, including but not limited to diagonally slotted circular, ring, and rectangular patches. A schematic diagram of the alternative structure is shown below. Figure 12 As shown. This can improve the unit's performance and enable it to have different polarization radiation capabilities, but it increases the design complexity.

[0042] In alternative power distribution circuits, the current approach uses a stripline structure with each T-shaped stub employing a uniformly distributed output characteristic. The final output amplitude distribution of the series feed network is 0.5012, 0.5012, 0.7079, 1, 1, 0.7079, 0.5012, 0.5012, while the parallel feed network has a uniform amplitude output. Alternatively, the parallel feed network can also be designed with a non-uniform amplitude distribution.

[0043] To achieve the aforementioned power distribution circuit with non-uniform amplitude distribution output, each stage's 1-to-2 T-type power divider will be designed with unequal power distribution. Taking a Chebyshev tapered distribution as an example, if the normalized weights of the feed amplitude for the 8-channel feed network are 0.6603, 0.6603, 0.8751, 1.0, 1.0, 0.8751, 0.6603, and 0.6603, respectively, then the sidelobe level of the achieved far-field beam scanning pattern can be suppressed from a uniform distribution of -13dB to -20dB. This increases the design freedom of the power distribution circuit and reduces sidelobes, but it also increases design complexity.

[0044] Among the alternatives to liquid crystal phase shifters, the currently used liquid crystal phase shifters use coplanar coupled bilinear structures with loaded metal strips as the main body. New topologies for liquid crystal phase shifters could be considered, such as using non-coplanar coupled bilinear structures with loaded coupling stubs, or a CPW structure could be used as the main body of the phase shifter. Thus, non-coplanar coupled bilinear structures with loaded coupling stubs can achieve extremely high phase shift per unit electrical length, which is beneficial for size reduction; however, the extremely strong loading may cause in-band resonance.

[0045] Among the alternatives to baluns, the current baluns are based on a planar microstrip line structure to construct a half-wavelength delay line to achieve differential output characteristics. Consideration could be given to constructing a Marchand balun using planar microstrip lines or a broadband balun based on a Schiffman phase shifter. Alternatively, the anti-phase coupling characteristic of a slot could be used to directly introduce an anti-phase electric field into the two microstrip lines at the output, thereby achieving a broadband, high-purity differential mode balun. A broadband balun can further improve the broadband characteristics of the phase shifter, and a balun with a high-purity differential mode output can make the frequency characteristics of the transmission coefficient of the liquid crystal phase shifter more uniform and stable. However, a broadband, high-purity differential mode balun will increase the circuit complexity of the planar microstrip line or slot-coupled structure.

[0046] The dual-polarized liquid crystal phased array (LCD) based on a dual-polarized radiating subarray and a liquid crystal phase shifter, proposed according to embodiments of the present invention, solves the problems of single radiating polarization and low aperture utilization in existing LCD phased arrays. The dual-polarized LCD phased array comprises three parts: a dual-polarized radiating subarray, a liquid crystal phase shifter, and a power divider. The dual-polarized radiating subarray is obtained by cascading multiple dual-polarized radiating elements using a series feed, and the tapered output characteristic of the series feed network gives the radiation pattern low sidelobe characteristics in the longitudinal direction. The dual-polarized radiating subarrays are connected in parallel via the power divider. The liquid crystal phase shifter, as the core component, can achieve continuous adjustment of the transmission phase by adjusting the bias voltage. Its two ends are connected to the radiating subarray and the power distribution circuit respectively through slot coupling, and all phase shifters are hidden below the array, without occupying additional space. Actual measurements show that the dual-polarized channels of this LCD phased array have a return loss of over 10dB and a port isolation of over 25dB within the design frequency band, and achieve beam scanning within ±40°, showing significant application prospects in future communication and other fields.

[0047] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0048] 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 as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "N" means at least two, such as two, three, etc., unless otherwise explicitly specified.

Claims

1. A dual-polarized liquid crystal phased array based on dual-polarized radiating sub-arrays and liquid crystal phase shifters, characterized in that, The dual-polarization liquid crystal phased array consists of three parts: a dual-polarization radiating subarray, a liquid crystal phase shifter, and a parallel-feed power divider. The dual-polarized radiating subarray comprises M dual-polarized radiating elements and two 1-to-8 series-fed power dividers. The M dual-polarized radiating elements are connected by cascaded series-fed power dividers, and the output ports of the series-fed power dividers are connected to the input ports of the dual-polarized radiating elements. In the longitudinal arrangement direction, each dual-polarized radiating subarray is connected to two liquid crystal phase shifters through slot coupling. In the transverse arrangement direction, N dual-polarized radiating subarrays are arranged periodically, and each dual-polarized radiating subarray is connected to two parallel-fed power dividers, resulting in a dual-polarized liquid crystal phased array with M×N elements. Wherein, M is the number of dual-polarized radiating elements in the dual-polarized radiating subarray, N is the number of dual-polarized radiating subarrays, M is an even number and M is greater than or equal to 2, the arrangement spacing of the dual-polarized radiating elements is 0.3λ g to 0.7λ g , wherein λ g is the central frequency wavelength.

2. The dual-polarized liquid crystal phased array based on dual-polarized radiation subarray and liquid crystal phase shifter according to claim 1, characterized in that, In terms of the stacked structure, the dual-polarized liquid crystal phased array is manufactured by mixing printed circuit boards and glass substrates, with the printed circuit boards and glass substrates being fabricated in steps and then pressed together to form the final dual-polarized liquid crystal phased array. The printed circuit board portion includes 5 dielectric substrate layers and 4 adhesive layers, with a total of 8 copper layers. The glass substrate includes 2 glass layers, filled with low-cell-thickness liquid crystal, and the inner surfaces of the 2 glass layers are covered with metal. The glass substrate and adhesive layers are bonded together with a single layer of adhesive. The dual-polarized radiating subarray and parallel-fed power divider of the dual-polarized liquid crystal phased array are implemented on the printed circuit board structure, while the liquid crystal phase shifter portion is implemented on the glass substrate portion.

3. The dual-polarized liquid crystal phased array based on dual-polarized radiation subarray and liquid crystal phase shifter of claim 1, wherein, The dual-polarized radiating element comprises three dielectric substrate layers and two adhesive layers, with a total of five copper layers. In terms of radiating structure, the dual-polarized radiating element adopts a stacked patch structure, with the two patches located on the upper and lower surfaces of the top dielectric substrate, respectively. In terms of feeding structure, it employs a feed stripline slot coupling feed, with the top and bottom metal grounds of the stripline located on the upper and lower surfaces of the middle dielectric substrate, respectively, and the inner conductor of the stripline located on the lower surface of the middle dielectric substrate. Two "I"-shaped slots are formed on the top metal ground directly below the projection of the stacked patch for slot coupling feeding. Between the top and bottom metal grounds, several metal pillars are formed around the antenna element and the edge of the slots to construct an isolation cavity, improving the isolation between the two polarizations. The ends of the two feed striplines are connected to two coaxial probes extending downwards for connection to the series feed power divider.

4. The dual-polarized liquid crystal phased array based on dual-polarized radiation subarray and liquid crystal phase shifter of claim 1, wherein, The series-fed power divider comprises two dielectric substrates and one adhesive layer, with a total of three copper layers. It employs a stripline structure, with the top and bottom metal grounds located on the upper and lower surfaces of the upper and lower dielectric substrates, respectively. The inner conductor of the stripline is located on the upper surface of the lower dielectric substrate. Several metal pillars are placed between the two ground layers to suppress unwanted parallel plate modes and improve stripline mode purity. The series-fed power divider consists of several matching stubs, several impedance transformation stubs, one coupling slot, and M-1 1-to-2 T-shaped stubs. It includes one output terminal coupled to the liquid crystal phase shifter via a slot. The series-fed power divider also includes M output terminals, each connected to a coaxial probe of one of the M dual-polarization units.

5. The dual-polarized liquid crystal phased array based on dual-polarized radiation subarray and liquid crystal phase shifter of claim 1, wherein, The corporate-fed power divider and the series-fed power divider adopt the same laminated structure and contain N output ports; the corporate-fed power divider is composed of a matching branch, a coupling slot and N-1 1:2 parallel T-shaped branches; the isolation cavity is constructed by punching holes between the upper and lower metal floors; the corporate-fed power divider contains one input end connected to an external radio frequency input port; and the corporate-fed power divider contains N outputs respectively connected to N liquid crystal phase shifters through a slot coupling.

6. The dual-polarized liquid crystal phased array based on dual-polarized radiation subarray and liquid crystal phase shifter of claim 1, wherein, The laminated structure of the liquid crystal phase shifter is an upper layer of glass, liquid crystal and a lower layer of glass, and the inner side of the glass is covered with a metal layer; the transmission type liquid crystal phase shifter is constructed based on the metal layer structure and specifically includes a balun structure, a parallel differential double line structure and a capacitive metal strip vertically loaded below the double line, the loaded capacitive metal strip and the differential double line overlap in the vertical orthographic projection, a variable capacitance is introduced to generate an adjustable phase shift; the phase shift unit is constructed by introducing the capacitive metal strip loading below the double line, and a plurality of phase shift units jointly constitute a phase shift section; all the capacitive metal strips are connected to a lower bias line, the differential double line structure is connected to an upper bias line, a bias voltage is applied between the upper and lower bias lines to realize the deflection of the liquid crystal molecules, and then the complete period regulation and control of the transmission phase of 360° is realized.

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