An adjustable balanced liquid crystal phase shifter

Abstract

The present invention discloses an adjustable balanced liquid crystal phase shifter, belonging to the technical field of microwave devices. The present invention solves the problem that the existing single-terminal adjustable liquid crystal phase shifter has poor electromagnetic interference resistance. The adjustable balanced liquid crystal phase shifter based on a coupled two-line structure, when a driving voltage is applied between the upper and lower coupled lines, the long axis directions of the liquid crystal molecules located between the upper and lower coupled lines will deflect, gradually deflecting from the horizontal direction to the vertical direction, thereby causing the dielectric constant of the liquid crystal material to change, and then the phase of the electromagnetic wave transmitted between the upper and lower coupled lines will change, ultimately realizing the function of the adjustable balanced liquid crystal phase shifter. The liquid crystal phase shifter structure provided by the present invention can enable the radio frequency signal to effectively propagate in the coupled two-line structure in a differential mode, and realize the continuous regulation of the transmission phase by controlling the change of the dielectric constant of the liquid crystal layer, thereby realizing the design of a balanced adjustable liquid crystal phase shifter based on the liquid crystal material and effectively improving the electromagnetic interference resistance ability.

Description

Technical Field

[0001] The present invention relates to an adjustable balanced liquid crystal phase shifter, belonging to the technical field of microwave devices. Background Art

[0002] An adjustable phase shifter is a microwave device for realizing phase regulation of radio frequency signals, which is widely used in fields such as antennas, radars, and wireless communications. Existing adjustable phase shifters are mainly realized by loading varactor diodes, ferroelectrics, graphene, or liquid crystals in the structure. The varactor diode has the advantages of a large tuning range and a simple design method, but due to the influence of the package lead inductance, it can only work in the low-frequency microwave band (below the X band). Although ferroelectrics and graphene can work in the frequency band above Ku, limited by the preparation process, the electromagnetic consistency of both ferroelectric thin film materials and graphene thin film materials cannot be effectively guaranteed.

[0003] Liquid crystal is an anisotropic material. As a uniaxial crystal, its molecular long axis has a specific direction. Under the action of an external electric field or magnetic field, the direction of the long axis of the liquid crystal molecules will deflect, thereby causing a change in the macroscopic dielectric constant of the liquid crystal material. Such a characteristic enables it to be applied in the design of microwave adjustable phase shifters. Compared with varactor diodes, ferroelectrics, and graphene materials, the adjustable phase shifter based on liquid crystal materials has many advantages such as a wide operating frequency range (from low frequency to terahertz), small volume, low profile, and stable performance. However, existing liquid crystal adjustable phase shifters generally adopt single-terminal transmission line structures such as inverted microstrip lines or coplanar waveguide transmission lines, resulting in poor electromagnetic interference resistance and severely limiting their practical application value. Summary of the Invention

[0004] Aiming at the problem of poor electromagnetic interference resistance of existing single-terminal adjustable liquid crystal phase shifters, the present invention provides an adjustable balanced liquid crystal phase shifter.

[0005] The technical solution of the present invention:

[0006] An adjustable balanced liquid crystal phase shifter includes, from top to bottom, an upper dielectric plate 1, an upper coupling line 2, a liquid crystal layer 3, a lower coupling line 4, a lower dielectric plate 5, and a metal ground 6. The upper dielectric plate 1 and the lower dielectric plate 5 are flat structures made of insulating materials. The insulating materials can be ordinary circuit board substrates or other materials such as glass, silicon dioxide, and ceramics that have a certain hardness and low electromagnetic loss. The upper coupling line 2 is located on the lower surface of the upper dielectric plate 1, the lower coupling line 4 is located on the upper surface of the lower dielectric plate 5, the liquid crystal layer 3 is located between the upper dielectric plate 1 and the lower dielectric plate 5, and the metal ground 6 is located on the lower surface of the lower dielectric plate 5;

[0007] Taking the length direction of the upper dielectric plate 1 as the y-axis direction, the width direction as the x-axis direction, and the height direction as the z-axis direction;

[0008] The structures of the upper coupling line 2 and the lower coupling line 4 are symmetrical. The structure of the lower coupling line 4 can be obtained by mirroring the upper coupling line 2 180° along the y-axis.

[0009] The upper coupling line 2 includes a microstrip line 7, a fan-shaped connection branch structure 8, and periodic stubs 9. The fan-shaped connection branch structure 8 and the periodic stubs 9 are respectively located on both sides of the microstrip line 7, and the fan-shaped connection branch structure 8 and the periodic stubs 9 are arranged opposite to each other. The fan-shaped connection branch structure 8 includes a fan-shaped structure and a branch structure, and the fan-shaped structure is connected to the microstrip line 7 through the branch structure.

[0010] The projection of the upper coupling line 2 on the lower dielectric substrate 5 overlaps with the lower coupling line 4.

[0011] Further defined, the thickness of the upper dielectric substrate 1 is h1, the thickness of the upper coupling line 2 is t1, the thickness of the liquid crystal layer 3 is h3, the thickness of the lower coupling line 4 is t2, and the thickness of the lower dielectric substrate 5 is h2.

[0012] Further defined, the projection of the periodic stubs 9 of the upper coupling line 2 on the lower dielectric substrate 5 overlaps with the periodic stubs 9 of the lower coupling line 4, and the overlapping length is l4.

[0013] Further defined, the width of the microstrip line 7 is w1, the distance between adjacent periodic stubs 9 is w2, the radius of the fan-shaped structure is r, the radian is θ, and the branch structure is a rectangle with a length of l1 and a width of w4.

[0014] Further defined, starting from both ends of the upper coupling line 2 and moving towards the central direction, the length of the periodic stubs 9 gradually increases with an equal tolerance until it reaches l2 and remains unchanged.

[0015] Further defined, the upper coupling line 2 is symmetrical along the central axis of the upper dielectric substrate 1 in the x-axis direction.

[0016] Further defined, the parameter value range of the upper coupling line 2 is:

[0017] l1≤0.25λ g 、0.1λ g ≤l2≤0.2λ g 、l4<l2、0.005λ g ≤w1≤0.1λ g 、0.1λ g ≤w2≤0.15λ g 、0.01λ g ≤w3≤0.2λ g 、0.005λ g ≤w4≤0.2λ g 、r<w2、30°≤θ≤180°, where λ gis the medium wavelength corresponding to the working center frequency.

[0018] It is further defined that, starting from the two ends of the upper coupling line 2 toward the center, the lengths of the periodic branches 9 are k 01 , k 02 and l2, where l2-k 02 =k 02 -k 01 .

[0019] It is further defined that the length of the upper dielectric plate 1 and the lower dielectric plate 5 is l4 and the width is w3.

[0020] It is further defined that the operating frequency band of the liquid crystal phase shifter is 5-10 GHz, and the specific parameter values are:

[0021] k 01 =2.5mm, k 02 =3.0mm, l1=2.5mm, l2=3.5mm, l3=30.0mm, l4=3.2mm, w1=1.2mm, w2=2.7mm, w3=0.3mm, w 4=0.1mm, r=1.5mm, θ=90°, h1=0.7mm, h2=0.7mm, h3=0.005mm, t1=0.002mm and t2=0.002mm;

[0022] The electrical parameter of the liquid crystal material of the liquid crystal layer 3 is ε r，⊥ =2.5,ε r， / / =3.2,tanδ ⊥ =0.0143 and tanδ / / =0.0056.

[0023] It is further defined that the upper coupling line 2 and the lower coupling line 4 are both metal film structures, and the lower surface of the upper dielectric plate 1 and the upper surface of the lower dielectric plate 5 are manufactured by printing, etching and other methods.

[0024] It is further defined that the surface of the liquid crystal layer 3 has a liquid crystal alignment layer to ensure that the long axes of the liquid crystal molecules of the liquid crystal layer 3 point to the horizontal direction (the direction perpendicular to the z-axis) when no driving voltage is applied.

[0025] It is further defined that the preparation process of the liquid crystal layer 3 is:

[0026] Objects such as microspheres, spacers or dielectric columns are arranged between the upper dielectric plate 1 and the lower dielectric plate 5 to maintain a gap of height h3 between the upper dielectric plate 1 and the lower dielectric plate 5, and then liquid crystal material is poured or sprayed into the gap to form a liquid crystal layer.

[0027] It is further defined that the upper dielectric plate 1 and the lower dielectric plate 5 are made of Rogers 4350B material.

[0028] The present invention has the following beneficial effects: The adjustable balanced liquid crystal phase shifter based on a coupled two-line structure of the present invention applies a driving voltage between the upper coupling line and the lower coupling line. The long axis directions of the liquid crystal molecules located between the periodic branches of the upper and lower coupling lines will deflect, gradually deflecting from the horizontal direction (the direction perpendicular to the z-axis) to the vertical direction (the direction parallel to the z-axis), thereby changing the dielectric constant of the liquid crystal material. This change will cause the phase of the electromagnetic wave transmitted between the upper and lower coupling lines to change, ultimately realizing the function of the adjustable balanced liquid crystal phase shifter.

[0029] The present invention has the following advantages:

[0030] (1) At both ends of the upper coupling line and the lower coupling line of the present invention, in order to enable the adjustable balanced liquid crystal phase shifter to have better mode matching and impedance matching effects (wider operating bandwidth), the lengths of the first two metal branches at both ends of the upper coupling line and the lower coupling line adopt a tapered form. Moreover, if more metal branches at both ends of the upper and lower coupling lines adopt a tapered form, the impedance matching and mode matching effects of the adjustable balanced liquid crystal phase shifter will be better, and the operating bandwidth will be wider;

[0031] (2) The liquid crystal phase shifter structure provided by the present invention enables the radio frequency signal to effectively propagate in the coupled two-line structure in a differential mode. By controlling the change of the dielectric constant of the liquid crystal layer, continuous regulation of the transmission phase is achieved, and thus the design of the balanced adjustable liquid crystal phase shifter based on the liquid crystal material is realized, effectively improving the ability to resist electromagnetic interference;

[0032] (3) Compared with the existing adjustable liquid crystal phase shifters, the liquid crystal phase shifter structure provided by the present invention has strong anti-noise interference ability, making it of important value in the application of integrated circuits. Moreover, it also has the significant advantages of simple and efficient design solutions. Brief Description of the Drawings

[0033] Figure 1 is a three-dimensional structural schematic diagram of the adjustable balanced liquid crystal phase shifter provided by the present invention;

[0034] Figure 2 is a side view of the adjustable balanced liquid crystal phase shifter provided by the present invention;

[0035] Figure 3 is a schematic diagram of the upper coupling line structure;

[0036] Figure 4 is a schematic diagram of the lower coupling line structure;

[0037] Figure 5 is the amplitude simulation result of the liquid crystal phase shifter S in Embodiment 1 11 ;

[0038] Figure 6The liquid crystal phase shifter S of Embodiment 1 21 Amplitude simulation result

[0039] Figure 7 The simulation result of the maximum adjustable phase shift amount of the liquid crystal phase shifter of Embodiment 1

[0040] Figure 8 The simulation result of the quality factor of the liquid crystal phase shifter of Embodiment 1

[0041] In the figure, 1 - upper dielectric plate, 2 - upper coupling line, 3 - liquid crystal layer, 4 - lower coupling line, 5 - lower dielectric plate, 6 - metal ground, 7 - microstrip line, 8 - fan-shaped connection branch structure, 9 - periodic stub Detailed implementation manners

[0042] In order to make the objectives, technical solutions and advantages 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 only used to explain the present invention, but not to limit the present invention

[0043] The experimental methods used in the following embodiments are all conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are all conventional materials, reagents, methods and instruments in the art, and those skilled in the art can obtain them through commercial channels without special instructions

[0044] Embodiment 1

[0045] This embodiment provides an adjustable balanced liquid crystal phase shifter operating in the 5 - 10 GHz frequency band

[0046] As shown in Figures 1-4 , the liquid crystal phase shifter includes, from top to bottom along the z-axis, an upper dielectric plate 1, an upper coupling line 2, a liquid crystal layer 3, a lower coupling line 4, a lower dielectric plate 5 and a metal ground 6. The upper dielectric plate 1 and the lower dielectric plate 5 are flat structures made of insulating materials. The upper coupling line 2 is located on the lower surface of the upper dielectric plate 1, the lower coupling line 4 is located on the upper surface of the lower dielectric plate 5, the liquid crystal layer 3 is located between the upper dielectric plate 1 and the lower dielectric plate 5, and the metal ground 6 is located on the lower surface of the lower dielectric plate 5. The thickness of the upper dielectric plate 1 is h1, the thickness of the upper coupling line 2 is t1, the thickness of the liquid crystal layer 3 is h3, the thickness of the lower coupling line 4 is t2, the thickness of the lower dielectric plate 5 is h2, and the length of the upper dielectric plate 1 and the lower dielectric plate 5 is l4 and the width is w3

[0047] The structures of the upper coupling line 2 and the lower coupling line 4 are symmetrical. The structure of the lower coupling line 4 can be obtained by mirroring the upper coupling line 2 along the y-axis and flipping it 180°. The upper coupling line 2 includes a microstrip line 7, a fan-shaped connection branch structure 8, and periodic stubs 9. The fan-shaped connection branch structure 8 and the periodic stubs 9 are respectively located on both sides of the microstrip line 7, and the fan-shaped connection branch structure 8 and the periodic stubs 9 are arranged opposite to each other. The fan-shaped connection branch structure 8 includes a fan-shaped structure and a branch structure. The fan-shaped structure is connected to the microstrip line 7 through the branch structure. The projection of the periodic stub 9 of the upper coupling line 2 on the lower dielectric substrate 5 overlaps with the periodic stub 9 of the lower coupling line 4, and the overlapping length is l4. The width of the microstrip line 7 is w1, the distance between adjacent periodic stubs 9 is w2, the radius of the fan-shaped structure is r, the radian is θ, and the branch structure is a rectangle with a length of l1 and a width of w4.

[0048] Starting from both ends of the upper coupling line 2 and moving towards the central direction, the length of the periodic stub 9 gradually increases with an equal tolerance until it reaches l2 and remains unchanged. The lengths of the periodic stubs 9 are successively k 01 , k 02 and l2, where l2 - k 02 = k 02 - k 01 .

[0049] The structural parameters of this liquid crystal phase shifter are set as follows:

[0050] k 01 = 2.5 mm, k 02 = 3.0 mm, l1 = 2.5 mm, l2 = 3.5 mm, l3 = 30.0 mm, l4 = 3.2 mm, w1 = 1.2 mm, w2 = 2.7 mm, w3 = 0.3 mm, w4 = 0.1 mm, r = 1.5 mm, θ = 90°, h1 = 0.7 mm, h2 = 0.7 mm, h3 = 0.005 mm, t1 = 0.002 mm, and t2 = 0.002 mm.

[0051] In addition, the upper dielectric substrate 1 and the lower dielectric substrate 5 are Rogers 4350B. The electrical parameters of the liquid crystal material of the liquid crystal layer 3 are ε r，⊥ = 2.5, ε r， / / = 3.2, tanδ ⊥ = 0.0143, and tanδ / / = 0.0056.

[0052] Based on the above structural parameters and material properties, the simulation results of this liquid crystal phase shifter are as shown in Figures 5-8 shown, from Figures 5-8It can be seen that regardless of whether the long axis of the liquid crystal molecules points horizontally or vertically, the S11 amplitude of the designed tunable balanced liquid crystal phase shifter is less than -18 dB within the operating frequency band of 5 GHz - 10 GHz, achieving good impedance matching. At the same time, within the frequency band of 5 GHz - 10 GHz, the insertion loss (S21 amplitude) of the designed tunable balanced liquid crystal phase shifter is always less than 4.2 dB, and the maximum tunable phase shift amount is always greater than 62°. Therefore, the figure of merit of this tunable balanced liquid crystal phase shifter is always greater than 30° / dB. Therefore, the above simulation results show that the tunable balanced liquid crystal phase shifter proposed in this patent can achieve good phase control function.

[0053] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. An adjustable balanced liquid crystal phase shifter, characterized in that, From top to bottom, it includes an upper dielectric plate (1), an upper coupling line (2), a liquid crystal layer (3), a lower coupling line (4), a lower dielectric plate (5), and a metal ground (6). The upper dielectric plate (1) and the lower dielectric plate (5) are flat structures made of insulating materials. The upper coupling line (2) is located on the lower surface of the upper dielectric plate (1), the lower coupling line (4) is located on the upper surface of the lower dielectric plate (5), the liquid crystal layer (3) is located between the upper dielectric plate (1) and the lower dielectric plate (5), and the metal ground (6) is located on the lower surface of the lower dielectric plate (5). Taking the length direction of the upper dielectric plate (1) as the y-axis direction, the width direction as the x-axis direction, and the height direction as the z-axis direction; The structures of the upper coupling line (2) and the lower coupling line (4) are symmetric. Flipping the upper coupling line (2) 180° along the y-axis by mirror image gives the structure of the lower coupling line (4). The upper coupling line (2) includes a microstrip line (7), a fan-shaped connection branch structure (8), and periodic stubs (9). The fan-shaped connection branch structure (8) and the periodic stubs (9) are respectively located on both sides of the microstrip line (7), and the fan-shaped connection branch structure (8) and the periodic stubs (9) are arranged facing each other. The fan-shaped connection branch structure (8) includes a fan-shaped structure and a branch structure, and the fan-shaped structure is connected to the microstrip line (7) through the branch structure. The projection of the upper coupling line (2) on the lower dielectric plate (5) overlaps with the lower coupling line (4).

2. The adjustable balanced liquid crystal phase shifter according to claim 1, wherein The thickness of the upper dielectric layer (1) is h 1, the thickness of the upper coupling line (2) is t 1, the thickness of the liquid crystal layer (3) is h 3, the thickness of the lower coupling line (4) is t 2, the thickness of the lower dielectric layer (5) is h 2.

3. The adjustable balanced liquid crystal phase shifter according to claim 2, wherein, The projection of the periodic stubs (9) of the upper coupling line (2) on the lower dielectric substrate (5) overlaps with the periodic stubs (9) of the lower coupling line (4), and the overlapping length is l 4.

4. The adjustable balanced liquid crystal phase shifter according to claim 3, wherein The width of the microstrip line (7) is w 1, the distance between adjacent periodic branches (9) is w 2, the radius of the fan-shaped structure is r , the radian is , the branch structure is a rectangle with a length of l 1 and a width of w 4.

5. An adjustable balanced liquid crystal phase shifter according to claim 4, characterized in that, Starting from both ends of the upper coupling line (2) and moving towards the central direction, the length tolerance of the periodic stub (9) gradually increases until it reaches l 2 remains unchanged.

6. The adjustable balanced liquid crystal phase shifter according to claim 5, wherein The upper coupling line (2) is symmetric along the center line of the upper dielectric plate (1) in the x-axis direction.

7. An adjustable balanced liquid crystal phase shifter according to claim 6, characterized in that, The parameter value range of the upper coupling line (2) is: , , l 4 < l 2, , , , , , , where is the medium wavelength corresponding to the working center frequency; The operating frequency band range of the liquid crystal phase shifter is 5 - 10 GHz; The electrical parameters of the liquid crystal material of the liquid crystal layer (3) are , , and .

8. An adjustable balanced liquid crystal phase shifter according to claim 7, characterized in that, Starting from both ends of the upper coupling line (2) and moving towards the central direction, the lengths of the periodic stubs (9) are successively k 01 、 k 02 and l 2, where l 2 - k 02 = k 02 - k 01 。 9. The adjustable balanced liquid crystal phase shifter according to claim 8, wherein The lengths of the upper dielectric plate (1) and the lower dielectric plate (5) are l 3, and the widths are w 3.

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