Liquid crystal phase shifter with broadside coupling transition structure

Abstract

The application provides a liquid crystal phase shifter with a wide-side coupling transition structure, which at least comprises: a same-side coupling structure, a delay line type liquid crystal phase shifter and a different-side coupling structure; wherein the same-side coupling structure refers to a coupling structure on the same side of the metal ground of the liquid crystal layer, and the different-side coupling structure refers to a coupling structure on the upper and lower sides of the metal ground of the liquid crystal layer. Transmission of signals in and out of the glass layer of the electrically controlled liquid crystal element is realized by designing two different cross-layer coupling transition structures, so that an ultra-wideband working frequency band and lower loss are realized.

Description

Technical Field

[0001] This invention relates to the field of liquid crystal phase shifters, and particularly to a liquid crystal phase shifter with a wide-side coupling transition structure. Background Technology

[0002] Phase shifters are key components in phased array radar and communication systems, playing a crucial role in the overall system performance. With the rapid development of the communication industry, the requirements for phase shifters are becoming increasingly stringent. Developing phase shifters with low loss, large phase difference, compact structure, and low cost is of great significance.

[0003] Currently, the main method for adjusting the phase shift of phase shifters is through electrical tuning, generally based on PIN diodes, varactor diodes, MEMS, ferroelectrics, or ferrites. PIN diodes cannot achieve continuously adjustable phase and exhibit significant losses and parasitic effects at high frequencies. Phase shifters based on varactor diodes can achieve continuously adjustable phase, but also suffer from significant losses and parasitic effects at high frequencies. Phase shifters based on MEMS devices outperform PIN diodes and varactor diodes in performance, but are costly and difficult to integrate. Ferroelectric materials allow for a wide range of dielectric constant tuning and perform well at lower frequencies, but require high bias voltages for tuning. Furthermore, as the frequency increases, material losses increase, leading to increased phase shifter losses; therefore, ferroelectric materials are unsuitable for Ku-frequency ranges and even higher. Ferrite-based phase shifters can use external magnetic fields to influence the material's permeability, thereby altering the phase velocity of electromagnetic waves. However, they require high driving power and are bulky and heavy, hindering the miniaturization of tunable phase shifters. The above materials cannot simultaneously meet the requirements of compactness, low cost, and continuous tuning.

[0004] Liquid crystals have attracted researchers' attention for many years due to their wide range of applications in both optical and non-optical fields. Because liquid crystal molecules are sensitive to electromagnetic fields, exhibit relatively low dielectric loss, and related devices are inexpensive to manufacture, they hold significant research value in microwave and millimeter-wave circuits. Liquid crystals possess strong electrical tunability; their characteristics can be controlled through surface anchoring, external electric or magnetic fields, and they exhibit different dielectric constants under different voltages. Therefore, compared to other tunable media, liquid crystals are increasingly widely used in various microwave devices, such as tunable phase shifters, antennas, capacitors, resonators, and filters. Phase shifters based on liquid crystal materials offer advantages such as continuous phase modulation, miniaturization, and low cost. However, research shows that current liquid crystal phase shifters are mostly used in narrowband applications, and designs covering the C, X, and Ku bands with low loss are difficult to achieve. Summary of the Invention

[0005] The technical problem this invention aims to solve is that: currently, high-precision liquid crystal packaging mainly uses glass as the material; however, it is difficult to achieve metal vias in glass manufacturing processes, making it challenging to physically connect the transmission lines inside the phase shifter to the external phase shifter. To overcome the shortcomings of existing technologies, this invention designs two different cross-layer coupling structures to achieve signal transmission both inside and outside the glass layer of the electronically controlled liquid crystal element, achieving an ultra-wideband operating frequency band and lower loss.

[0006] To achieve the above objectives, a liquid crystal phase shifter with a wide-side coupling transition structure is provided, comprising at least: a same-side coupling structure, a delayed linear liquid crystal phase shifter, and an opposite-side coupling structure. The same-side coupling structure refers to a coupling structure on the same side of the liquid crystal layer metal ground, i.e., the mid-layer slotted metal ground plate 8, while the opposite-side coupling structure refers to a coupling structure on both sides of the liquid crystal layer metal ground.

[0007] Same-side coupling structures have:

[0008] The structure comprises a lower metal ground plane 1, a first metal via 2, a lower dielectric substrate 3, a lower coupling line 4, a lower glass substrate 5, an upper coupling line 6-1, a liquid crystal layer 7, and a middle slotted metal ground plane 8. This structure forms a wide-side coupled stripline structure under a non-uniform dielectric layer. Signals are transmitted via a coaxial connector through the first metal via 2 to the lower coupling line 4, and further coupled to the upper coupling line 6-1. The upper coupling line 6-1 is connected to the phase-shifting line 6-2, thereby achieving vertical interconnection between the phase-shifting line and the lower external structure.

[0009] Phase-shifting linear liquid crystal phase shifters have the following characteristics:

[0010] The structure comprises a lower glass substrate 5, a phase-shifting line 6-2, a liquid crystal layer 7, a middle slotted metal ground plane 8, and an upper glass substrate 9. This structure constitutes an inverted microstrip line structure. By changing the bias voltage applied to the liquid crystal layer 7, continuous phase modulation is achieved using the phase-shifting line 6-2.

[0011] The opposite-side coupling structure has:

[0012] The structure comprises a lower metal ground plane 1, a lower dielectric substrate 3, a lower glass substrate 5, a lower coupling patch 6-3, a liquid crystal layer 7, a middle slotted metal ground plane 8, an upper glass substrate 9, an upper coupling patch 10, an upper dielectric substrate 11, and an upper metal ground plane 13. This structure constitutes a cross-layer transition structure based on a slotted metal ground plane under non-uniform dielectric conditions. The phase shift line 6-2 is connected to the lower coupling patch 6-3, and the signal is coupled to the upper coupling patch 10 through the lower coupling patch 6-3, thereby achieving vertical interconnection between the phase shift line and the upper external structure.

[0013] The overall signal transmission path is as follows: first, the input feed line is connected through a coaxial connector, and then coupled to the phase-shifting line 6-2 inside the lower glass substrate 5 by the same-side coupling structure. The phase shifting purpose is achieved by changing the dielectric constant of the liquid crystal by applying a bias voltage to the liquid crystal. Then, at the end of the phase-shifting line 6-2, the signal is coupled to the upper coupling patch 10 of the upper glass substrate 9 through the opposite-side coupling structure, and then output through the coaxial connector.

[0014] The advantages of this invention compared to the prior art are:

[0015] This invention employs a mature process based on glass-encapsulated liquid crystal, offering excellent airtightness and stability. By designing two different coupling structures, the input and output are located on the upper and lower sides of the phase shifter, facilitating cascading design with a phased array antenna. Broadband design of the two coupling structures achieves an ultra-wideband operating frequency band of 6-18 GHz. Bending the coupling structure and phase shifter to increase the line length further increases the phase shift amount while also achieving a degree of miniaturization. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0017] Figure 1 This is a three-dimensional structural diagram of the same-side coupling structure in an embodiment of the present invention;

[0018] Figure 2 This is a front view schematic diagram of the same-side coupling structure in an embodiment of the present invention;

[0019] Figure 3 This is a top view of the same-side coupling structure in an embodiment of the present invention;

[0020] Figure 4 This is a three-dimensional structural diagram of the opposite-side coupling structure in an embodiment of the present invention;

[0021] Figure 5 This is a front view schematic diagram of the opposite-side coupling structure in an embodiment of the present invention;

[0022] Figure 6 This is a top view of the opposite-side coupling structure in an embodiment of the present invention;

[0023] Figure 7 This is a three-dimensional structural diagram of the phase shifter in an embodiment of the present invention;

[0024] Figure 8This is a front view of the phase shifter as a whole in an embodiment of the present invention;

[0025] Figure 9 This is a top view of the phase shifter as described in an embodiment of the present invention;

[0026] Figure 10 This is a schematic diagram of the overall phase shifting result of the phase shifter in an embodiment of the present invention;

[0027] Figure 11 S is the overall phase shifter in the embodiment of the present invention. 11 Schematic diagram;

[0028] Figure 12 S is the overall phase shifter in the embodiment of the present invention. 21 Schematic diagram. Detailed Implementation

[0029] This invention provides a liquid crystal phase shifter with a wide-side coupling transition structure. The liquid crystal phase shifter includes a same-side coupling structure, a delay line liquid crystal phase shifter, and an opposite-side coupling structure. In this embodiment, based on the design requirements of the wideband coupling structure, patches of different shapes are loaded at the beginning and end of the phase shift line inside the liquid crystal phase shifter and matched with the phase shift line. The inverted microstrip line structure is designed to match a 50Ω characteristic impedance; however, due to the shift in the equivalent dielectric constant, a mismatch of several ohms in the characteristic impedance occurs. The parity-mode analysis method of the coupling line is used to design the same-side coupling structure. A wide-side coupling stripline directional coupler is selected as the basic structure for the same-side coupling. Simulation tools are used to calculate the parity-mode impedance of the wide-side coupling stripline medium, using a dielectric substrate-glass-liquid crystal as the medium. This is achieved by analyzing the line length and line width of different stripline segments. The offset distance of the coupling line is optimized to approximate the theoretical value of the wide-side coupled stripline structure in the traditional homogeneous medium case calculated by the odd-even mode analysis method. The multi-segment stripline design broadens the working bandwidth of the coupled line structure. The coupling degree of the overall same-side coupled structure is improved by cascading multiple coupled line structures. The opposite-side coupled structure consists of multiple microstrip lines and striplines on the top and bottom, respectively, which improves the impedance matching performance. The square slot is used to allow energy to pass through the middle, which provides the basis for broadband coupling structure. The basic structure is optimized by using a pre-trained deep learning model with good generalization, and then branches are added to the transmission line for impedance matching.

[0030] This invention innovatively applies the even-odd mode analysis method to the design of wide-side coupled stripline directional couplers with multilayer dielectrics and different dielectric layer thicknesses. Based on this, a same-side cross-layer transition structure is designed, which greatly improves the operating bandwidth of the traditional coupling transition structure and reduces operating losses. Furthermore, this invention innovatively uses a generative adversarial network model to optimize the cross-metal floor transition structure. By training, a predictive model with good generalization is obtained to optimize the opposite-side cross-layer transition coupling structure under dielectric variation conditions, which broadens its operating bandwidth and achieves good matching with the feeder, further reducing operating losses.

[0031] The present invention will be described in detail below with reference to the figures and specific embodiments, but this is not intended to limit the present invention.

[0032] like Figures 1-3 As shown, a same-side coupling structure based on a non-uniform layer wide-side coupling stripline structure is proposed, including: a liquid crystal electronic control element encapsulated with a double-layer glass plate, a PCB layer and a dielectric substrate.

[0033] like Figure 2 As shown, the liquid crystal element is encapsulated using a glass substrate. From bottom to top, each layer consists of: a lower glass substrate 5, a phase shifter layer 6, the phase shifter layer 6 including an upper coupling line 6-1, a phase shifter 6-2, a liquid crystal layer 7, a middle slotted metal ground plane 8, and an upper glass substrate 9. The liquid crystal layer has a thickness of 0.1 mm, the glass substrate has a thickness of 0.3 mm, and the phase shifter width is 0.18 mm.

[0034] The dielectric substrate 3 is mounted on the underside of the lower glass substrate 5 of the liquid crystal element and is bonded together by an adhesive layer. Both the upper and lower sides of the dielectric substrate 3 have PCB layers. The PCB layer on the lower surface serves as the lower metal ground plane 1, while the PCB layer on the upper surface is designed as a lower coupling line 4, coupling with the upper coupling line 6-1 inside the liquid crystal element. The dielectric substrate 3 has a first metal via 2 connected to the lower coupling line 4. The dielectric substrate is made of Rogers 4350 material, with a thickness of 0.8 mm, and the radius of the first metal via 2 is 0.13 mm.

[0035] like Figure 1 As shown, two interleaved coupled striplines are cascaded to improve coupling. The signal is input from the coaxial port of the lower metal ground plane 1, and coupled to the upper coupling line 6-1 through the first metal via 2 and the lower coupling line 4. The open section of the lower coupling line 4 is connected to a 50-ohm matching load through the same metal via. The coupling output terminal of the upper coupling line 6-1 is connected to the phase shift line 6-2.

[0036] like Figures 4-6 As shown, a non-side coupling structure based on a slotted metal floor is proposed, comprising: a liquid crystal electronic control element encapsulated with a double-layer glass plate, a PCB layer, and a dielectric substrate.

[0037] like Figure 5 As shown, the dielectric substrate 11 is mounted on top of the upper glass substrate 9 of the same liquid crystal element and is connected as a single unit by an adhesive layer. Both the upper and lower sides of the dielectric substrate 11 have PCB layers. The upper PCB layer serves as the upper metal ground plane 13, and the lower PCB layer is designed as the upper coupling patch 10. The dielectric substrate 11 has a second metallized via 12 connected to the transmission line portion of the upper coupling patch 10. The dielectric substrate 11 is made of Rogers 4350 material, has a thickness of 0.8 mm, and the radius of the second metal via 12 is 0.13 mm.

[0038] like Figure 4 As shown, the lower coupling patch 6-3 couples energy to the upper coupling patch 10 through the middle slotted metal ground plate 8. The output end of the upper coupling patch 10 is connected to the second metal via 12 through a transmission line. The signal is output from the coaxial interface of the upper metal ground plate 13 through the second metal via 12.

[0039] Figures 7-9 For the overall structure of the phase shifter, the previously designed same-side coupling structure and opposite-side coupling structure are connected to the phase-shifting linear liquid crystal element to form a complete signal transmission path. The signal is input from the signal input port of the lower ground plane and output from the signal output port of the upper ground plane. The phase-shifting line layer 6 and the slotted metal ground plane layer 8 serve as electrodes of the liquid crystal element. By applying a bias voltage to change the dielectric constant of the liquid crystal, the phase on the phase-shifting line changes continuously. Different voltage values ​​can achieve differential phase shift. The phase shifter consists of: a lower glass substrate 5, a phase-shifting line 6-2, a liquid crystal layer 7, a middle slotted metal ground plane 8, and an upper glass substrate 9. The above structure constitutes an inverted microstrip line structure. By changing the bias voltage applied to the liquid crystal layer 7, the phase-shifting line 6-2 is used to achieve continuous phase modulation. The result of its phase change with frequency is as follows: Figure 10 As shown, the S-parameter diagrams of the overall structure are as follows: Figure 11 and Figure 12 As shown.

[0040] The parts of this invention not described in detail are well-known to those skilled in the art.

[0041] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A liquid crystal phase shifter with a wide-side coupling transition structure, characterized in that, The liquid crystal phase shifter includes at least: a same-side coupling structure, a delayed linear liquid crystal phase shifter, and an opposite-side coupling structure; wherein, the same-side coupling structure refers to the coupling structure on the same side of the liquid crystal layer metal ground, i.e., the middle layer slotted metal floor (8), and the opposite-side coupling structure refers to the coupling structure on the upper and lower sides of the liquid crystal layer metal ground. The same-side coupling structure includes: a lower metal ground plane (1), a first metal via (2), a lower dielectric substrate (3), a lower coupling line (4), a lower glass substrate (5), an upper coupling line (6-1), a liquid crystal layer (7), and a middle slotted metal ground plane (8); the signal is transmitted from the coaxial connector to the lower coupling line (4) through the first metal via (2), and further coupled to the upper coupling line (6-1). The upper coupling line (6-1) is connected to the phase shift line (6-2) of the delayed linear liquid crystal phase shifter, thereby realizing the vertical interconnection between the phase shift line (6-2) and the lower external structure; The delayed-line liquid crystal phase shifter includes: a lower glass substrate (5), a phase shift line (6-2), a liquid crystal layer (7), a middle slotted metal ground plane (8), and an upper glass substrate (9); all of the above structures constitute an inverted microstrip line structure, and the continuous phase shifting function is achieved by changing the bias voltage applied to the liquid crystal layer (7) using the phase shift line (6-2). The opposite-side coupling structure includes: a lower metal ground plane (1), a lower dielectric substrate (3), a lower glass substrate (5), a lower coupling patch (6-3), a liquid crystal layer (7), a middle slotted metal ground plane (8), an upper glass substrate (9), an upper coupling patch (10), an upper dielectric substrate (11), and an upper metal ground plane (13). All of the above structures constitute a cross-layer transition structure based on a slotted metal ground plane under non-uniform dielectric conditions. The phase shift line (6-2) is connected to the lower coupling patch (6-3), and the signal is coupled to the upper coupling patch (10) through the lower coupling patch (6-3), thereby realizing the vertical interconnection between the phase shift line (6-2) and the upper external structure.

2. The liquid crystal phase shifter according to claim 1, characterized in that, The overall signal transmission path is as follows: first, the input feed line is connected through a coaxial connector, and then coupled to the phase-shifting line (6-2) inside the lower glass substrate (5) by the same-side coupling structure. The phase shifting purpose is achieved by applying a bias voltage to the liquid crystal to change the dielectric constant of the liquid crystal. Then, at the end of the phase-shifting line (6-2), the signal is coupled to the upper coupling patch (10) of the upper glass substrate (9) through the opposite-side coupling structure, and then output through the coaxial connector.

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