An electrically controlled liquid crystal radio frequency switch

Abstract

The present invention discloses an electrically controlled liquid crystal radio frequency switch, which belongs to the field of microwave device engineering technology. The present invention solves the problems that existing ferrite and ferroelectric material radio frequency switches require a large driving electric field or magnetic field, and the liquid crystal radio frequency switch has a large volume and low integration. The present invention realizes effective switching of the on and off states based on liquid crystal materials, and has the significant advantage of a small required external driving voltage. The electrically controlled liquid crystal radio frequency switch provided by the present invention adopts a parallel LC resonant circuit structure, which has the advantages of compact structure, miniaturization and high integration, and has good prospects for practical industrial applications.

Description

Technical Field

[0001] The invention relates to an 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. Microwave switches were implemented using PIN diodes and MEMS in the early days, but their scope of use was greatly limited due to problems such as difficulty in integration and low power tolerance. 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.

[0003] However, currently, both ferrite RF switches and ferroelectric RF switches often require a larger driving electric field or driving magnetic field due to the defects of the characteristics of ferrite and ferroelectric materials themselves. This causes the entire circuit system to be subject to greater electromagnetic interference, resulting in the overall system performance being unstable, and even in some extreme cases causing it to be unable to work and be used normally. Summary of the invention

[0004] The present invention provides an electrically controlled liquid crystal radio frequency switch to solve the problems that existing ferrite and ferroelectric material radio frequency switches require a large driving electric field or magnetic field, the liquid crystal radio frequency switch is large in size, and the integration is low.

[0005] The technical solution of the present invention:

[0006] An electrically controlled liquid crystal radio frequency switch, 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, wherein 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;

[0007] The microstrip structure 4 is a metal film including two mirror-symmetrical transmission line units and two high-impedance connections 10, each of the transmission line units including 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;

[0008] The two sides of the two inner microstrip transmission lines 9 are connected via high impedance lines 10 respectively;

[0009] The projection of the upper metal patch 2 on the lower dielectric plate 5 overlaps with the two inner microstrip transmission lines 9 .

[0010] It is further defined 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, the microstrip structure 4 and the metal ground 6 are all t.

[0011] It is further defined that the upper metal patch 2 is a rectangular metal film, and the width of the rectangular metal film is w 4 , the length is l 3 , where 0.02λ g ≤w 4 ≤0.05λ g , 0.02λ g ≤l 3 ≤0.3λ g ,λ g is the medium wavelength corresponding to the working center frequency.

[0012] 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 w 2 The width of the inner microstrip transmission line 9 and the upper bottom length of the gradient transmission line 8 are both w 1 , the height of the gradient transmission line 8 is l 1 , where 0.02λ g ≤w 2 ≤λ g , 0.02λ g ≤w 1 ≤0.1λ g , 0.06λ g ≤l 1 ≤0.15λ g ,λ g is the medium wavelength corresponding to the working center frequency.

[0013] It is further defined that the length of the high impedance connection 10 is l 2 , the distance between the two high impedance lines 10 is w 3 , where 0.02λ g ≤l 2 ≤0.15λ g , 0.04λ g ≤w 3 ≤0.1λ g ,λ g is the medium wavelength corresponding to the working center frequency.

[0014] Further definition, the RF switch operating frequency band range is 13.5-14GHz, and the specific parameter value is w 1 =0.3mm, w 2 =1.5mm, w 3 =0.9mm, w 4 =0.3mm, l 1 =1.1mm,l 2 =1.00mm, l 3 =1.3mm, t=0.005mm, h 1 =0.7mm,h 2 =0.005mm and h 3 =0.7mm, the electrical parameters of the upper dielectric plate 1 and the lower dielectric plate 5 are ε r =4.704 and tanδ=0.0048.

[0015] It is further defined that the electrical parameter of the liquid crystal material filled in the liquid crystal layer 3 is ε r，⊥ =2.24,ε r， / / =3.22, tanδ ⊥ =0.057 and tanδ / / =0.0039.

[0016] 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.

[0017] 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.

[0018] It is further defined that the preparation process of the liquid crystal layer 3 is:

[0019] 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 height h. 2The liquid crystal material is then poured or sprayed into the gap to form a liquid crystal layer.

[0020] Further defined, the upper metal patch 2 is a metal film structure made by printing, etching, etc. with a thickness of h 1 the lower surface.

[0021] It is further defined that the outer microstrip transmission line 7, the gradient transmission line 8, the inner microstrip transmission line 9 and the high impedance connection line 10 are all metal film structures, which are made by printing, etching and other methods with a thickness of h. 3 The upper surface of the lower dielectric plate 5.

[0022] The present invention has the following beneficial effects: the present invention realizes effective switching of on and off states based on liquid crystal materials, and has a significant advantage of requiring a small external driving voltage compared to radio frequency switches based on ferrite and ferroelectric materials. The electrically controlled liquid crystal radio frequency switch of the present invention adopts a parallel LC resonant circuit structure, has the advantages of compact structure, miniaturization and high integration, and has good prospects for practical industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0025] Figure 3 The simulation results of the transmission characteristics of the 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-high impedance connection, 11-projection of upper 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;

[0031] The microstrip structure 4 is a metal film including two mirror-symmetrical transmission line units and two high-impedance connections 10, each of the transmission line units including 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;

[0032] The two sides of the two inner microstrip transmission lines 9 are connected by high impedance lines 10, respectively, so as to generate the required equivalent parallel inductance;

[0033] The projection of the upper metal patch 2 on the lower dielectric plate 5 overlaps with the two inner microstrip transmission lines 9 (eg Figure 2 As shown in reference numeral 11).

[0034] The upper metal patch 2 is manufactured on the lower surface of the upper dielectric plate 1 by printing, etching or other methods, and the microstrip structure 4 is manufactured on the upper surface of the lower dielectric plate 5 by printing, etching or other methods.

[0035] The preparation process of the liquid crystal layer 3 is as follows: a microsphere, a spacer or a dielectric column or the like is arranged between the upper dielectric plate 1 and the lower dielectric plate 5 to keep the upper dielectric plate 1 and the lower dielectric plate 5 to form a height h. 2 The liquid crystal material is then poured or sprayed into the gap to form a liquid crystal layer.

[0036] The thickness of the upper dielectric plate 1 is h 1 =0.7mm, the thickness of the liquid crystal layer 3 is h 2 =0.005mm, the thickness of the lower dielectric plate 5 is h 3 =0.7mm, the thickness of the upper metal patch 2, the microstrip structure 4 and the metal ground 6 are all t=0.005mm.

[0037] The upper metal patch 2 is a rectangular metal film, and the width of the rectangular metal film is w 4 =0.3mm, length is l 3=1.3mm.

[0038] The width of the outer microstrip transmission line 7 and the bottom length of the gradient transmission line 8 are both w 2 =1.5mm, the width of the inner microstrip transmission line 9 and the upper bottom length of the gradient transmission line 8 are both w 1 =0.3mm, the height of the gradient transmission line 8 is l 1 =1.1mm.

[0039] The length of the high impedance connection 10 is l 2 =1.00mm, the distance between the two high impedance lines 10 is w 3 =0.9mm.

[0040] 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 material filled in the liquid crystal layer 3 are ε r，⊥ =2.24,ε r， / / =3.22, tanδ ⊥ =0.057 and tanδ / / =0.0039.

[0041] 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 to the horizontal direction, the corresponding transmission zero point is 12.5GHz, and the corresponding insertion loss (S21 amplitude) is 9dB; 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 13.7GHz, and the insertion loss (S21 amplitude) is 6.6dB at this time, and the insertion loss (S21 amplitude) of the orientation state at this frequency point is only 0.8dB. In addition, within the frequency band range of 13.5-14GHz, its insertion loss (S21) is always less than 1.1dB when the switch is on, and the insertion loss (S21 amplitude) is always greater than 6dB when it is off. Therefore, the above simulation results show that the liquid crystal RF switch proposed in this patent can achieve good electromagnetic wave on-off control within the frequency band range of 13.5-14GHz.

[0042] 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. An 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 microstrip structure (4) is a metal film including two transmission line units in mirror symmetry and two high impedance lines (10), each of the transmission line units including 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 two sides of the two inner microstrip transmission lines (9) are respectively connected via high impedance lines (10); The projection of the upper metal patch (2) on the lower dielectric plate (5) overlaps with the two inner microstrip transmission lines (9); The upper metal patch (2) is a rectangular metal film, and the width of the rectangular metal film is w 4, length is l 3, among which , , is the medium wavelength corresponding to the working center frequency.

2. The 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. The electrically controlled liquid crystal radio frequency switch according to claim 2, 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 bottom length of the gradient transmission line (8) are both w 1, the height of the gradient transmission line (8) is l 1, where , , , is the medium wavelength corresponding to the working center frequency.

4. The electrically controlled liquid crystal radio frequency switch according to claim 3, characterized in that: The length of the high impedance connection (10) is l 2. The distance between the two high impedance lines (10) is w 3, among which , , is the medium wavelength corresponding to the working center frequency.

5. The electrically controlled liquid crystal radio frequency switch according to claim 4, characterized in that: The operating frequency band of the RF switch is 13.5-14 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 .

6. The electrically controlled liquid crystal radio frequency switch according to claim 5, characterized in that: The electrical parameters of the liquid crystal material of the liquid crystal layer (3) are: , , and .

7. The 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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