A compact electrically controlled liquid crystal radio frequency switch

Abstract

The present invention discloses a compact electrically controlled liquid crystal radio frequency switch, which belongs to the field of microwave device engineering technology. The present invention solves the problem of large size and low integration of existing liquid crystal radio frequency switches. The electrically controlled liquid crystal radio frequency switch provided by the present invention has the characteristics of high integration, small size and miniaturization, which improves the applicable scenarios of liquid crystal radio frequency switches in practical applications. Compared with the existing radio frequency switches, the electrically controlled liquid crystal radio frequency switch of the present invention adopts the form of two resonant circuits in cascade, realizing a good switching ratio, and the radio frequency switch realizes effective switching of the on and off states based on liquid crystal materials. Compared with the traditional radio frequency switches based on ferrite and ferroelectric materials, it has the significant advantage of small required external driving voltage.

Description

Technical Field

[0001] The invention relates to a compact electrically controlled liquid crystal radio frequency switch, belonging to the technical field of microwave device engineering. Background Art

[0002] With the continuous advancement and innovation of science and technology, people have increasingly stringent requirements for RF components in communication systems. In RF circuit systems, RF switches are important components in RF front-end systems and are currently widely used to control microwave signal paths in radar and communication systems. In recent years, with the continuous breakthroughs in the field of controllable electromagnetic materials, RF switch technology based on electrically controllable media has made great progress. RF switches based on ferrite and ferroelectric materials have higher power capacity and better integration, so they are widely used in phased array radar systems. However, at present, whether it is a ferrite RF switch or a ferroelectric RF switch, due to the limitations of the characteristics of ferrite and ferroelectric materials themselves, they often require a larger driving electric field or driving magnetic field, which makes the circuit system as a whole subject to greater electromagnetic interference, resulting in a greater impact on system performance, and even in some extreme cases, it cannot operate normally.

[0003] Liquid crystal is an anisotropic material. As a uniaxial crystal, its molecular long axis has a specific orientation. Under the action of an external electric field or magnetic field, the orientation of the long axis of the liquid crystal molecule will deflect, causing the macroscopic dielectric constant of the liquid crystal material to change. This characteristic allows it to be used in the design of RF switches. Since the external driving voltage required by liquid crystal materials is relatively small, the problem of large electromagnetic interference in RF switches based on ferrite or ferroelectric materials can be solved.

[0004] However, the existing liquid crystal radio frequency switches are large in size and low in integration, which makes them unable to be used in circuit systems with small space and compact structure, seriously limiting their practical application value. Summary of the invention

[0005] In order to solve the problems of large volume and low integration of existing liquid crystal radio frequency switches, the present invention provides a compact electrically controlled liquid crystal radio frequency switch.

[0006] The technical solution of the present invention:

[0007] A compact electrically controlled liquid crystal radio frequency switch comprises, from top to bottom, an upper dielectric plate 1, an upper metal patch 2, a liquid crystal layer 3, a microstrip structure 4, a lower dielectric plate 5 and a metal ground 6. The upper dielectric plate 1 and the lower dielectric plate 5 are flat plate structures made of insulating material. The upper metal patch 2 is located on the lower surface of the upper dielectric plate 1, the microstrip structure 4 is located on the upper surface of the lower dielectric plate 5, the liquid crystal layer 3 is located between the upper metal patch 2 and the microstrip structure 4, and the metal ground 6 is located on the lower surface of the lower dielectric plate 5. The projection of the upper metal patch 2 on the lower dielectric plate 5 overlaps with the microstrip structure 4.

[0008] It is further defined that the thickness of the upper dielectric plate 1 is h1, the thickness of the liquid crystal layer 3 is h2, the thickness of the lower dielectric plate 5 is h3, and the thicknesses of the upper metal patch 2, the microstrip structure 4 and the metal ground 6 are all t.

[0009] Further defined, the upper metal patch 2 is two equal and parallel rectangular metal films, the width of the rectangular metal film is w4, the length is l3, the outer edge distance of the two metal films is l4, where 0.06λ g ≤w4≤0.3λ g , 0.02λ g ≤l3≤0.1λ g ,l2≤l4≤0.3λ g ,λ g is the medium wavelength corresponding to the working center frequency.

[0010] It is further defined that the microstrip structure 4 is a metal film including two transmission line units in mirror symmetry, two L-shaped connecting lines 10 and a lower metal patch 11, each of the transmission line units includes an outer microstrip transmission line 7, a gradient transmission line 8 and an inner microstrip transmission line 9, the outer microstrip transmission line 7 and the inner microstrip transmission line 9 are both rectangular structures, the gradient transmission line 8 is a trapezoidal structure, the upper base of the trapezoid is connected to the inner microstrip transmission line 9, the lower base of the trapezoid is connected to the outer microstrip transmission line 7, and the two inner microstrip transmission lines 9 are adjacent;

[0011] The lower metal patch 11 is a rectangular structure located on one side of the two inner microstrip transmission lines 9 , and both ends of the lower metal patch 11 are connected to the inner microstrip transmission lines 9 via L-shaped connecting lines 10 .

[0012] It is further defined that the projection of the upper metal patch 2 on the lower dielectric plate 5 overlaps with the two inner microstrip transmission lines 9 of the microstrip structure 4 and the lower metal patch 11, and the overlapping length of the projection of the upper metal patch 2 on the lower dielectric plate 5 and the two inner microstrip transmission lines 9 is l3.

[0013] It is further defined that the width of the outer microstrip transmission line 7 and the bottom length of the gradient transmission line 8 are both w2, the width of the inner microstrip transmission line 9 and the top length of the gradient transmission line 8 are both w1, and the height of the gradient transmission line 8 is l1; wherein 0.02λ g ≤w2≤0.5λ g , 0.1λ g ≤w1≤0.3λ g , 0.06λ g ≤l1≤0.3λ g ,λ g is the medium wavelength corresponding to the working center frequency.

[0014] It is further defined that the distance between the lower metal patch 11 and the outer edge of the inner microstrip transmission line 9 is w4.

[0015] It is further defined that the width of the lower metal patch 11 is w5 and the length is l2, where 0.02λ g ≤w5≤0.2λ g , 0.04λ g ≤l2≤0.2λ g , the length of the L-type connecting line is w3, 0.05λ g ≤w3≤0.1λ g ,λ g is the medium wavelength corresponding to the working center frequency.

[0016] It is further defined that the operating frequency band of the RF switch is 16.4-17.3 GHz, and the specific parameter values ​​are w1=1.2 mm, w2=0.4 mm, w3=0.5 mm, w4=1.5 mm, w5=0.4 mm, l1=1.2 mm, l2=0.8 mm, l3=0.3 mm, l4=0.8 mm, t=0.005 mm, h1=0.7 mm, h2=0.005 mm and h3=0.7 mm. The electrical parameters of the upper dielectric plate 1 and the lower dielectric plate 5 are ε r =4.704 and tanδ=0.0048, the electrical parameters of the liquid crystal layer are ε r，⊥ =2.24,ε r， / / =3.22, tanδ ⊥ =0.057 and tanδ / / =0.0039.

[0017] 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 when no driving voltage is applied.

[0018] It is further defined that the upper dielectric plate 1 and the lower dielectric plate 5 are flat plate structures made of insulating material, and the insulating material can be a common circuit board substrate or other materials with a certain hardness and low electromagnetic loss such as glass, silicon dioxide, ceramics, etc.

[0019] It is further defined that the preparation process of the liquid crystal layer 3 is:

[0020] 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 h2 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.

[0021] It is further defined that the upper metal patch 2, the outer microstrip transmission line 7, the gradient transmission line 8, the inner microstrip transmission line 9, the L-shaped connecting line 10 and the lower metal patch 11 are all metal film structures, which are manufactured on the upper surface of the lower dielectric plate 5 with a thickness of h3 by printing, etching and other methods.

[0022] The present invention has the following beneficial effects: the electrically controlled liquid crystal radio frequency switch provided by the present invention has the characteristics of high integration, small size and miniaturization, which improves the applicable scenarios of liquid crystal radio frequency switches in practical applications. Compared with the existing radio frequency switches, the electrically controlled liquid crystal radio frequency switch of the present invention adopts the form of two resonant circuits in cascade, thereby achieving a good switching ratio. The radio frequency switch realizes effective switching of the on and off states based on liquid crystal materials. Compared with traditional radio frequency switches based on ferrite and ferroelectric materials, it has the significant advantage of a small required external driving voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of the three-dimensional structure of a compact electrically controlled liquid crystal radio frequency switch provided by the present invention;

[0024] Figure 2 A schematic diagram of the microstrip structure of the compact electrically controlled liquid crystal radio frequency switch provided by the present invention;

[0025] Figure 3 The transmission characteristics simulation results of the compact electrically controlled liquid crystal radio frequency switch provided by the present invention;

[0026] In the figure, 1-upper dielectric plate, 2-upper metal patch, 3-liquid crystal layer, 4-microstrip structure, 5-lower dielectric plate, 6-metal ground, 7-outer microstrip transmission line, 8-gradient transmission line, 9-inner microstrip transmission line, 10-L-type connecting line, 11-lower metal patch. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0028] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.

[0029] Embodiment 1:

[0030] This embodiment provides an electrically controlled liquid crystal radio frequency switch operating in the Ku band. Figure 1-Figure 2 As shown, the electrically controlled liquid crystal radio frequency switch includes an upper dielectric plate 1, an upper metal patch 2, a liquid crystal layer 3, a microstrip structure 4, a lower dielectric plate 5 and a metal ground 6 from top to bottom along the z-axis. The upper dielectric plate 1 and the lower dielectric plate 5 are flat plate structures made of insulating materials. The upper metal patch 2 is located on the lower surface of the upper dielectric plate 1, the microstrip structure 4 is located on the upper surface of the lower dielectric plate 5, the liquid crystal layer 3 is located between the upper metal patch 2 and the microstrip structure 4, and the metal ground 6 is located on the lower surface of the lower dielectric plate 5; the projection of the upper metal patch 2 on the lower dielectric plate 5 overlaps with the microstrip structure 4 (as shown in FIG. 1 ). Figure 2 The dotted line portion is shown).

[0031] The upper metal patch 2 and the microstrip structure 4 are made on the upper surface of the lower dielectric plate 5 by printing, etching and other methods. The preparation process of the liquid crystal layer 3 is as follows: objects such as microspheres, spacers or dielectric columns are arranged between the upper dielectric plate 1 and the lower dielectric plate 5 to maintain the upper dielectric plate 1 and the lower dielectric plate 5 to form a gap with a height of h2, and then the liquid crystal material is poured or sprayed into the gap to form a liquid crystal layer.

[0032] The thickness of the upper dielectric plate 1 is h1 = 0.7 mm, the thickness of the liquid crystal layer 3 is h2 = 0.005 mm, and the thickness of the lower dielectric plate 5 is h3 = 0.7 mm.

[0033] The upper metal patch 2 is two rectangular metal films of equal size and parallel to each other, with a width of w4 and a length of l3. The distance between the outer edges of the two metal films is l4, where w4=1.5mm, l3=0.3mm, and l4=0.8mm.

[0034] The microstrip structure 4 is a metal film including two transmission line units in mirror symmetry, two L-shaped connecting lines 10 and a lower metal patch 11. Each of the transmission line units includes an outer microstrip transmission line 7, a gradient transmission line 8 and an inner microstrip transmission line 9. The outer microstrip transmission line 7 and the inner microstrip transmission line 9 are both rectangular structures, and the gradient transmission line 8 is a trapezoidal structure. The outer microstrip transmission line 7 has a width of w2 = 0.4 mm and is connected to the inner microstrip transmission line 9 with a width of w1 = 1.2 mm through the gradient transmission line 8 with a length of l1 = 1.2 mm. The inner microstrip transmission line 9 is connected to the lower metal patch 11 with a length of l2 = 0.8 mm and a width of w5 = 0.4 mm through the L-shaped connecting line 10 with a length of w3 = 0.5 mm.

[0035] The projection of the upper metal patch 2 on the lower dielectric plate 5 overlaps with the two inner microstrip transmission lines 9 of the microstrip structure 4 and the lower metal patch 11, and the overlapping length of the projection of the upper metal patch 2 on the lower dielectric plate 5 and the two inner microstrip transmission lines 9 is the same as the length of the rectangular metal film of the upper metal patch 2.

[0036] The distance between the lower metal patch 11 and the outer edge of the inner microstrip transmission line 9 is the same as the width of the rectangular metal film of the upper metal patch 2 .

[0037] The electrical parameters of the upper dielectric plate 1 and the lower dielectric plate 5 are ε r =4.704 and tanδ=0.0048, the electrical parameters of the liquid crystal layer are ε r，⊥ =2.24,ε r， / / =3.22, tanδ ⊥ =0.057 and tanδ / / =0.0039.

[0038] The upper metal patch 2 and the microstrip line structure 4 serve as the upper electrode and the lower electrode of the liquid crystal drive of the above structure respectively. When a voltage is applied between the upper metal patch 2 and the microstrip line layer, the direction of the liquid crystal molecules between the two will be deflected, and the direction of the long axis of the liquid crystal molecules will gradually deflect 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 and finally realizing an adjustable RF switching function.

[0039] Based on the above structural parameters and material properties, the simulation results of the transmission characteristics of the electrically controlled liquid crystal RF switch are as follows: Figure 3 As shown by Figure 3 It can be seen that when the liquid crystal molecules point in the horizontal direction, the corresponding transmission zero point is 15.2 GHz, and the corresponding insertion loss (S 21 The amplitude) is 20.4dB; when the liquid crystal molecules are in a vertical state under the action of an external bias electric field, the corresponding transmission zero point switches to 17.0GHz, at which time the insertion loss (S21 The insertion loss of the switch in the on state (S 21 Amplitude) is always less than 2dB, while the insertion loss in the off state (S 21 Therefore, it can be seen from the above simulation results that the liquid crystal RF switch proposed in this embodiment can achieve good electromagnetic wave on-off control in the frequency band range of 16.4-17.3 GHz.

[0040] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A compact electrically controlled liquid crystal radio frequency switch, characterized in that: The radio frequency switch comprises, from top to bottom, an upper dielectric plate (1), an upper metal patch (2), a liquid crystal layer (3), a microstrip structure (4), a lower dielectric plate (5) and a metal ground (6); the upper dielectric plate (1) and the lower dielectric plate (5) are flat plate structures made of insulating material; the upper metal patch (2) is located on the lower surface of the upper dielectric plate (1); the microstrip structure (4) is located on the upper surface of the lower dielectric plate (5); the liquid crystal layer (3) is located between the upper metal patch (2) and the microstrip structure (4); and the metal ground (6) is located on the lower surface of the lower dielectric plate (5); the projection of the upper metal patch (2) on the lower dielectric plate (5) overlaps with the microstrip structure (4); The upper metal patch (2) is two rectangular metal films of equal size and parallel to each other; The microstrip structure (4) is a metal film including two mirror-symmetrical transmission line units, two L A type connecting line (10) and a lower metal patch (11), each of the transmission line units comprises an outer microstrip transmission line (7), a gradient transmission line (8) and an inner microstrip transmission line (9), the outer microstrip transmission line (7) and the inner microstrip transmission line (9) are both rectangular structures, the gradient transmission line (8) is a trapezoidal structure, the upper base of the trapezoid is connected to the inner microstrip transmission line (9), the lower base of the trapezoid is connected to the outer microstrip transmission line (7), and the two inner microstrip transmission lines (9) are adjacent; The lower metal patch (11) is a rectangular structure located on one side of the two inner microstrip transmission lines (9), and the two ends of the lower metal patch (11) are respectively connected by L The type connecting line (10) is connected to the inner microstrip transmission line (9); The projection of the upper metal patch (2) on the lower dielectric plate (5) overlaps with two inner microstrip transmission lines (9) of the microstrip structure (4) and the lower metal patch (11).

2. A compact electrically controlled liquid crystal radio frequency switch according to claim 1, characterized in that: The thickness of the upper dielectric plate (1) is h 1. The thickness of the liquid crystal layer (3) is h 2. The thickness of the lower dielectric plate (5) is h 3. The thickness of the upper metal patch (2), microstrip structure (4) and metal ground (6) are t .

3. A compact electrically controlled liquid crystal radio frequency switch according to claim 2, characterized in that: The width of the rectangular metal film constituting the upper metal patch (2) is w 4, length is l 3. The distance between the outer edges of the two metal films is l 4, among which , , , is the medium wavelength corresponding to the working center frequency, where l 2 is the length of the lower metal patch (11).

4. A compact electrically controlled liquid crystal radio frequency switch according to claim 3, characterized in that: The overlap length of the projection of the upper metal patch (2) on the lower dielectric plate (5) and the two inner microstrip transmission lines (9) is l 3.

5. A compact electrically controlled liquid crystal radio frequency switch according to claim 4, characterized in that: The width of the outer microstrip transmission line (7) and the bottom length of the gradient transmission line (8) are both w 2. The width of the inner microstrip transmission line (9) and the upper and lower lengths of the gradient transmission line (8) are equal. w 1, the height of the gradient transmission line (8) is l 1; among which , , , is the medium wavelength corresponding to the working center frequency.

6. A compact electrically controlled liquid crystal radio frequency switch according to claim 5, characterized in that: The distance between the lower metal patch (11) and the outer edge of the inner microstrip transmission line (9) is w 4.

7. A compact electrically controlled liquid crystal radio frequency switch according to claim 6, characterized in that: The width of the lower metal patch (11) is w 5, length is l 2, where , , L The length of the connecting line is w 3. , is the medium wavelength corresponding to the working center frequency.

8. A compact electrically controlled liquid crystal radio frequency switch according to claim 7, characterized in that: The operating frequency band of the RF switch is 16.4 - 17.3 GHz, and the specific parameter values ​​are , , , , , , , , , , and The electrical parameters of the upper dielectric plate (1) and the lower dielectric plate (5) are: and , the electrical parameters of the liquid crystal layer are , , and .

9. The compact electrically controlled liquid crystal radio frequency switch according to claim 1, characterized in that: The surface of the liquid crystal layer (3) is provided with a liquid crystal orientation layer, which ensures that the long axes of the liquid crystal molecules of the liquid crystal layer (3) point in the horizontal direction when no driving voltage is applied.

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