Ultra-wideband same-side coupling transition structure based on liquid crystal material

Abstract

The invention provides an ultra-wideband same-side coupling transition structure based on a liquid crystal material, and relates to the field of liquid crystal devices, and strip lines in the same-side coupling transition structure are distributed on the same side of a liquid crystal layer. The coupling transition structure is composed of staggered vertical coupling strip lines which are distributed on the upper surface and the lower surface of the glass substrate and are in mirror symmetry. The designed four-port network can be used for building an equivalent circuit of a directional coupler under the condition of a non-uniform medium, transmission of signals inside and outside a glass layer of the electronic control liquid crystal element is achieved by designing a cross-layer coupling transition structure, and an ultra-wideband working frequency band and low loss are achieved.

Description

Technical Field

[0001] The invention relates to the field of liquid crystal devices, and in particular to an ultra-wideband same-side coupling transition structure based on liquid crystal materials. Background Art

[0002] A coupled transition structure is a design that achieves smooth transition and energy transfer between different transmission lines or different physical structures. This structure is commonly used in microwave and RF systems to ensure efficient and low-loss conversion of signals between different transmission media. The design of coupled transition structures is critical to maintaining the overall performance of the system, especially in high-frequency applications, where improper transitions may cause signal reflection, attenuation or interference, affecting the stability and reliability of the system.

[0003] Liquid crystal has attracted the attention of researchers for many years due to its wide application in optical and non-optical fields. Liquid crystal molecules are sensitive to electromagnetic fields, have relatively low dielectric loss, and the manufacturing cost of related devices is low, making them of great research value in microwave and millimeter wave circuits. Liquid crystal has strong electrical tunability, and its characteristics can be controlled by surface anchoring, external electric field or magnetic field. Under different voltages, liquid crystals exhibit different dielectric constants.

[0004] Due to the limitation of processing technology, the glass substrate encapsulating the liquid crystal cannot be metallized through holes. To achieve signal transmission inside and outside the liquid crystal phase shifter, coupling can only be used. Traditionally, in order to achieve a better coupling effect, a uniform medium is usually used. This structure is often used in the design of directional couplers with high coupling. The commonly used analysis method for the coupled line model is the odd-even mode analysis method. The odd-even mode analysis method is to decompose the mode transmitted in the coupled line into the mode under odd-mode excitation and even-mode excitation. Since the coupled transmission line is a linear system, the characteristic parameters under the two excitation modes can be calculated separately and then superimposed to obtain the overall characteristic parameters of the coupled line. The general process is to derive the odd and even mode impedances respectively, and then calculate the physical size of the coupled line. However, in the inhomogeneous medium, the odd-mode phase velocity in the coupler is not equal to the even-mode phase velocity. The performance of the coupled line designed according to the traditional design method is too much. Therefore, it is urgent to use unconventional design methods to design the coupled line transition structure under inhomogeneous media. Summary of the invention

[0005] When it comes to the coupling line transition structure in the case of inhomogeneous media, the original uniform medium in the traditional model is replaced by a three-layer inhomogeneous medium of liquid crystal-glass-dielectric plate from top to bottom, and the dielectric constant of the liquid crystal will change with the voltage. The conventional odd-even mode analysis method is no longer applicable to this coupling line structure. In order to solve the above technical problems, the present invention provides an ultra-wideband same-side coupling transition structure based on liquid crystal material, which realizes the transmission of signals inside and outside the glass layer of the electrically controlled liquid crystal element, and realizes an ultra-wideband operating frequency band and lower loss.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: An ultra-wideband same-side coupling transition structure based on liquid crystal material at least comprises: staggered vertical coupling strip lines distributed on the upper and lower sides of a dielectric substrate in a mirror-symmetrical manner; wherein the same-side coupling structure refers to a coupling structure on the same side of a liquid crystal layer.

[0007] Preferably, the staggered vertically coupled strip lines include a lower metal floor, a lower dielectric substrate, a lower strip transmission line, a lower strip coupling line, a glass substrate, an upper strip transmission line, an upper strip coupling line, a liquid crystal layer, and a top metal floor, which are arranged in sequence from bottom to top.

[0008] Preferably, the overall transmission path of the signal is: first, the feed line is input from the feed input port through a coaxial connector, coupled to the upper strip coupling line on the glass substrate by the same-side coupling structure, and then the signal is output through the coaxial connector through the coupling port located at the end of the upper strip transmission line.

[0009] Preferably, the lower strip transmission line connects the lower strip coupling line with the input port and the through port, and the upper strip transmission line connects the upper strip coupling line with the coupling port and the isolation port.

[0010] Preferably, the lower dielectric substrate, the lower circuit, the glass substrate, the upper circuit, and the liquid crystal layer together constitute a coupler under an asymmetric and inhomogeneous medium.

[0011] Compared with the prior art, the present invention has the following beneficial effects: The present invention adopts a mature process based on glass plate encapsulation of liquid crystal, which has good air tightness and stability. By designing staggered vertical coupling strip lines distributed on the upper and lower sides of the dielectric substrate in a mirror-symmetrical manner, cross-layer coupling in non-uniform media is achieved, and ultra-wideband working frequency band is achieved by broadband design of the coupling structure. The present invention applies the odd-even mode analysis method to the design of multi-layer dielectrics and stripline directional couplers with different dielectric layer thicknesses, and designs a same-side cross-layer transition structure based on this, which greatly improves the working bandwidth of the traditional coupling transition structure and reduces the working loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0013] Figure 1A schematic diagram of a three-dimensional structure of an ultra-wideband same-side coupling transition structure based on liquid crystal material driven by an embodiment of the present invention; Figure 2 It is a front view schematic diagram of an ultra-wideband same-side coupling transition structure based on liquid crystal material according to an embodiment of the present invention; Figure 3 A schematic top view of an ultra-wideband same-side coupling transition structure based on liquid crystal material according to an embodiment of the present invention; Figure 4 A schematic side view of an ultra-wideband same-side coupling transition structure based on liquid crystal material according to an embodiment of the present invention; Figure 5 Schematic diagram of the return loss S11 of the entire phase shifter in an embodiment of the present invention; Figure 6 Schematic diagram of the insertion loss S21 of the entire phase shifter in an embodiment of the present invention; Figure 7 Schematic diagram of the overall coupling degree S31 of the phase shifter in an embodiment of the present invention; Figure 8 FIG. 4 is a schematic diagram of the overall isolation S41 of the phase shifter in an embodiment of the present invention.

[0014] Among them, the figure markings are: lower metal floor 1, lower dielectric substrate 2, lower circuit 3, lower strip transmission line 3-1, lower strip coupling line 3-2, glass substrate 4, upper circuit 5, upper strip transmission line 5-1, upper strip coupling line 5-2, liquid crystal layer 6, top metal floor 7, input port 1#, through port 2#, coupling port 3#, isolation port 4#. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solutions 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. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0016] For the coupled line transition structure under the inhomogeneous medium involved in the liquid crystal phase shifter to be designed, the original uniform medium under the traditional model is replaced by a three-layer inhomogeneous medium of liquid crystal-glass-medium plate from top to bottom, and the dielectric constant of the liquid crystal will change with the voltage. There is no doubt that the conventional odd-even mode analysis method is no longer applicable to the design of this coupled line structure. Due to the inhomogeneous medium, the odd-mode phase velocity in the coupler is not equal to the even-mode phase velocity. The performance of the coupled line designed according to the traditional design method is too much reduced. Therefore, it is necessary to adopt an unconventional design method to design the coupled line transition structure under the inhomogeneous medium.

[0017] The ultra-wideband same-side coupling transition structure based on liquid crystal material of the present invention can be regarded as a directional coupler with high coupling degree requirements. However, it is difficult to achieve a high coupling degree at the central working frequency point even if a multi-section 1 / 4 wavelength wide-side coupled strip line is used to achieve a high coupling degree. At present, most 3dB couplers in the literature are based on two 8.34 dB strip line couplers cascaded to meet the design requirements; and to expand the working bandwidth of the coupling transition structure, it is necessary to refer to the design of a multi-section symmetrical directional coupler based on a wide-side coupled line, which can be equivalent to a 1 / 4 wavelength filter under a uniform medium. When designing, the working center frequency is designed to be 12GHz, the relative bandwidth is 100%, and the normalized even-mode impedance value table of the Chebyshev coupled transmission line directional coupler is searched to obtain the normalized even-mode impedance.

[0018] The present invention is described in detail below with reference to the drawings and specific embodiments, but is not intended to limit the present invention.

[0019] like Figure 1-Figure 4 As shown, an ultra-wideband same-side coupling transition structure based on liquid crystal material of the present invention includes a glass plate, a liquid crystal plate, a strip line, a metal floor and a dielectric substrate.

[0020] like Figure 2 As shown, the liquid crystal panel is encapsulated by a glass plate, and each layer from bottom to top is: a lower metal floor 1, a lower dielectric substrate 2, a lower circuit 3, a glass substrate 4, an upper circuit 5, a liquid crystal layer 6, and a top metal floor 7. The lower circuit 3 is composed of a lower strip transmission line 3-1 and a lower strip coupling line 3-2. The upper circuit 5 is composed of an upper strip transmission line 5-1 and an upper strip coupling line 5-2. The lower strip transmission line (3-1) connects the lower strip coupling line (3-2) with input port 1# and through port 2#, and the upper strip transmission line 5-1 connects the upper strip coupling line 5-2 with coupling port 3# and isolation port 4#.

[0021] The upper and lower parts of the ultra-wideband same-side coupling transition structure are provided with metal floors, namely, the lower metal floor 1 and the top metal floor 7, which are used to maintain the independence of the device. The lower circuit 3 is located between the lower dielectric substrate 2 and the glass substrate 4, and is connected as a whole by an adhesive layer. The upper side of the glass substrate 4 is the upper circuit 5. The lower circuit 3 and the upper circuit 5 are mirror-symmetrical to each other, forming a reciprocal four-port network. The upper side of the upper circuit 5 is the liquid crystal layer 6. The lower dielectric substrate 2, the lower circuit 3, the glass substrate 4, the upper circuit 5 and the liquid crystal layer 6 together constitute a coupler under an asymmetric and inhomogeneous medium. Among them, the material of the lower dielectric substrate 2 is Rogers3003, the thickness is 1.127mm, and the stripline width of the circuit is 0.1mm.

[0022] like Figure 1 and Figure 4As shown, the same-side coupling transition structure uses two sections of staggered coupled strip lines in cascade to improve the coupling degree. The signal is input from the coaxial input port 1#, transmitted to the lower strip coupling line 3-2 through the lower strip transmission line 3-1, transmitted to the upper strip coupling line 5-2 in the coupling area, and output from the coupling port 3# through the upper strip transmission line 5-1. The four ports are input port 1#, straight-through port 2#, coupling port 3#, and isolation port 4#. The straight-through port 2# is located at the end of the lower strip transmission line 3-1, opposite to the input port 1#, and is used to test the loss of coupling energy. The isolation port 4# is located at the starting end of the upper strip transmission line 5-1, on the same side as the input port 1#, and is used to characterize the decoupling power.

[0023] Figure 4-Figure 8 The overall S parameters of the device under different liquid crystal dielectric constants are shown, representing the return loss, insertion loss, coupling, and isolation of the device.

[0024] The present invention does not elaborate on some of the well-known technologies that belong to those skilled in the art.

[0025] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, technicians familiar with the field may make various corresponding changes and deformations based on the present invention, but these corresponding changes and deformations should all fall within the scope of protection of the claims of the present invention.

Claims

1. An ultra-wideband same-side coupling transition structure based on liquid crystal material, characterized in that: At least: The staggered vertically coupled strip lines are distributed on the upper and lower sides of the dielectric substrate in a mirror-symmetrical manner; wherein the same-side coupling structure refers to the coupling structure on the same side of the liquid crystal layer.

2. The ultra-wideband same-side coupling transition structure based on liquid crystal material according to claim 1, characterized in that: The staggered vertically coupled strip lines include a lower metal floor (1), a lower dielectric substrate (2), a lower strip transmission line (3-1), a lower strip coupling line (3-2), a glass substrate (4), an upper strip transmission line (5-1), an upper strip coupling line (5-2), a liquid crystal layer (6), and a top metal floor (7) which are arranged in sequence from bottom to top.

3. The ultra-wideband same-side coupling transition structure based on liquid crystal material according to claim 2, characterized in that: The overall transmission path of the signal is: first, the feed line is input from the feed input port through a coaxial connector, coupled to the upper strip coupling line (5-2) on the glass substrate (4) by the same-side coupling structure, and then the signal is output through the coaxial connector through the coupling port located at the end of the upper strip transmission line (5-1).

4. The ultra-wideband same-side coupling transition structure based on liquid crystal material according to claim 1, characterized in that: The lower strip transmission line (3-1) connects the lower strip coupling line (3-2) with the input port and the through port, and the upper strip transmission line (5-1) connects the upper strip coupling line (5-2) with the coupling port and the isolation port.

5. The ultra-wideband same-side coupling transition structure based on liquid crystal material according to claim 1, characterized in that: The lower dielectric substrate (2), the lower circuit (3), the glass substrate (4), the upper circuit (5) and the liquid crystal layer (6) together constitute a coupler under an asymmetric and non-uniform medium.

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