A coplanar waveguide to stripline transition structure for liquid crystal phase shifters

Abstract

The present invention belongs to the field of communications technology and relates to a coplanar waveguide to stripline transition structure for liquid crystal phase shifters. The structure comprises a first dielectric substrate, a second dielectric substrate, a liquid crystal layer, and a third dielectric substrate, arranged sequentially from top to bottom. The first dielectric substrate has a first metal ground layer and a coupling window on its upper surface, and a metal conductor strip on its lower surface. The second dielectric substrate has a routing layer on its lower surface, and the third dielectric substrate has a second metal ground layer on its upper surface. To address the vertical interconnection of signals in liquid crystal phase shifters, the present invention proposes a vertically coupled feed structure that balances performance requirements. This structure achieves a coupling form that converts microwave signals from a glass substrate to a PCB substrate, and converts transmission signals from the coplanar waveguide between the glass layers to a stripline. The structure can subsequently be used as a test piece for liquid crystal phase shifters and liquid crystal antennas, connecting antenna units or testing liquid crystal phase shifters.

Description

Technical Field

[0001] The present invention belongs to the field of communication technology, and in particular relates to a coplanar waveguide to stripline transition structure applied to a liquid crystal phase shifter. Background Art

[0002] Coplanar waveguides, as microwave planar transmission lines with superior performance and ease of fabrication, are widely used in the millimeter-wave frequency band, offering performance advantages unmatched by microstrip lines. Stripline transmission lines consist of two grounded metal strips separated by a rectangular metal conductor strip with a width w and thickness t. Their TEM transmission mode offers advantages such as compact size and wide bandwidth, making them suitable for the fabrication of high-performance microwave passive components. Combining these two transmission structures facilitates the design of devices such as liquid crystal antennas and phase shifters.

[0003] As microwave device frequencies continue to increase, vertical signal interconnection between multilayer boards becomes increasingly difficult. Conventional PCB manufacturing techniques allow for vertical signal interconnection using specialized through-holes. The manufacturing process for liquid crystal antennas is similar to that of LCDs, where holes can be punched around the edges of the glass substrate. However, drilling holes through the center of the glass to achieve signal interconnection for microstrip antennas is more challenging, and presents numerous challenges with glass stability and liquid crystal packaging. Summary of the Invention

[0004] In view of this, the present invention provides a coplanar waveguide to stripline transition structure applied to a liquid crystal phase shifter, so as to solve the above-mentioned technical problems.

[0005] The technical solution of the present invention is:

[0006] A coplanar waveguide to stripline transition structure for a liquid crystal phase shifter, comprising:

[0007] A first dielectric substrate, a second dielectric substrate, a liquid crystal layer, and a third dielectric substrate are arranged in sequence from top to bottom;

[0008] in,

[0009] The upper surface of the first dielectric substrate is provided with a first metal layer and a coupling window, and the lower surface is provided with a metal conductor strip;

[0010] A wiring layer is provided on the lower surface of the second dielectric substrate;

[0011] A second metal layer is provided on the upper surface of the third dielectric substrate.

[0012] Furthermore, the second dielectric substrate and the third dielectric substrate are glass substrates.

[0013] Furthermore, the routing layer is a coplanar waveguide inner conductor.

[0014] Furthermore, a slot coupling groove is provided on the second metal layer.

[0015] Furthermore, the first dielectric substrate is a PCB substrate.

[0016] Furthermore, the coupling window is in an "H" shape.

[0017] Furthermore, the thickness of the first dielectric substrate is 0.12-0.13 mm, the thickness of the second dielectric substrate and the third dielectric substrate is 0.28-0.35 mm, the thickness of the routing layer and the second metal layer is 0.95-1.5 μm, the thickness of the liquid crystal layer 3 is 5.8-6.2 μm, and the copper cladding thickness of the first metal layer is 0.03-0.04 mm.

[0018] Furthermore, the thickness of the first dielectric substrate is 0.127 mm, the thickness of the second dielectric substrate and the third dielectric substrate is 0.3 mm, the thickness of the routing layer and the second metal layer is 1 μm, the thickness of the liquid crystal layer is 6 μm, and the copper cladding thickness of the first metal layer is 0.035 mm.

[0019] This invention provides a coplanar waveguide-to-stripline transition structure for liquid crystal phase shifters, capable of extracting signals from the liquid crystal phase shifter. Addressing the vertical interconnection issues of liquid crystal phase shifters, this invention proposes a vertically coupled feed structure that balances performance requirements. This structure achieves a coupling form that converts microwave signals from a glass substrate to a PCB substrate, and also converts transmission signals from the coplanar waveguide between the glass interlayers to a stripline. This structure can subsequently be used as a test piece for liquid crystal phase shifters and liquid crystal antennas, connecting antenna units or testing liquid crystal phase shifters. Its practicality is highly worthy of promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0021] Figure 2 It is a schematic diagram of the layered structure of the present invention;

[0022] Figure 3 It is a partial structural schematic diagram of the present invention;

[0023] Figure 4 It is a partial structural schematic diagram of the present invention;

[0024] Figure 5 It is a partial structural schematic diagram of the present invention. DETAILED DESCRIPTION

[0025] The present invention provides a transition structure from a coplanar waveguide to a stripline for a liquid crystal phase shifter. Figures 1 to 5The present invention is described with reference to a structural schematic diagram of FIG.

[0026] Example 1

[0027] A coplanar waveguide to stripline transition structure used in liquid crystal phase shifters, such as Figure 1 As shown, its structure includes a first dielectric substrate 1, a second dielectric substrate 2, a liquid crystal layer 3 and a third dielectric substrate 4 which are fixedly connected in sequence from top to bottom;

[0028] A first metal layer and a coupling window 5 are etched on the upper surface of the first dielectric substrate 1, and a metal conductor strip 6 is etched on the lower surface; a routing layer is etched on the lower surface of the second dielectric substrate 2; and a second metal layer is etched on the upper surface of the third dielectric substrate 4.

[0029] An embodiment of the present invention relates to a coplanar waveguide to stripline transition structure applied to a liquid crystal phase shifter, which is a vertically coupled feeding structure that realizes the function of converting the coplanar waveguide between glass interlayers to the stripline.

[0030] like Figure 1 and Figure 2 As shown, the main structure comprises a first dielectric substrate 1, a second dielectric substrate 2, a liquid crystal layer 3, and a third dielectric substrate 4, which are fixedly connected from top to bottom. A first metal ground layer and a coupling window 5 are etched on the top surface of the first dielectric substrate 1, and a metal conductor strip 6 is etched on the bottom surface. A routing layer is etched on the bottom surface of the second dielectric substrate 2. A second metal ground layer with a slot coupling slot 8 is etched on the top surface of the third dielectric substrate 4. The second and third dielectric substrates 2 and 4 are glass substrates, and their surface patterns are formed using a sputtering-photolithography process. A routing layer is etched on the bottom surface of the second dielectric substrate 2, and the routing layer is a coplanar waveguide inner conductor 7. The coplanar waveguide inner conductor 7 and the slot coupling slot 8 form the coplanar waveguide coupling structure. The coplanar waveguide transmission mode is the TEM mode, which has no cutoff frequency. The coplanar waveguide inner conductor 7 of the present invention is located on the bottom surface of the second dielectric substrate 2, and the outer conductor is the second metal ground layer attached to the third dielectric substrate 4.

[0031] The first dielectric substrate 1 is a PCB substrate. An H-shaped coupling window 5 is formed in the first metal layer on the upper surface of the PCB substrate, and a metal conductor strip 6 is etched on the lower surface of the PCB substrate. A stripline is a high-frequency transmission line with an inner conductor placed between two metal layers and surrounded by a dielectric. Its transmission mode is TEM mode. In the present invention, the stripline is composed of the first metal layer, the first dielectric substrate 1, the metal conductor strip 6, the second dielectric substrate 2, the liquid crystal layer 3, and the second metal layer. The inner conductor of the stripline is the metal conductor strip 6.

[0032] Coplanar waveguide transmission lines can be considered an evolution of coaxial cables, equivalent to an open coaxial cable with no electric or magnetic field components in the transmission direction. Striplines also have similar properties. Electromagnetic waves are transmitted in coplanar waveguides. By creating a slit in the coplanar waveguide's outer conductor and forming an open circuit, the electromagnetic waves transmitted in the coplanar waveguide pass through the glass layer and couple to the stripline. This vertical transition structure allows the coplanar waveguide within the glass substrate to be connected to the stripline, avoiding the process issues associated with glass drilling. This conversion structure can subsequently be applied to connecting liquid crystal antenna radiating elements or testing liquid crystal phase shifters.

[0033] Specifically, the thickness of the first dielectric substrate 1 is 0.12-0.13 mm, the thickness of the second dielectric substrate 2 and the third dielectric substrate 4 is 0.28-0.35 mm, the copper cladding thickness of the routing layer and the second metal layer is 0.95-1.5 μm, the thickness of the liquid crystal layer 3 is 5.8-6.2 μm, and the copper cladding thickness of the first metal layer is 0.03-0.04 mm.

[0034] Among them, Figure 1 As shown, the thickness of the first dielectric substrate 1 is 0.127 mm, the copper cladding thickness of the first metal layer thereon is 0.035 mm, the thickness of the second dielectric substrate 2 and the third dielectric substrate 4 is 0.3 mm, the copper cladding thickness of the routing layer and the second metal layer thereon is 1 μm, and the thickness of the liquid crystal layer 3 is 6 μm.

[0035] like Figure 3 It shows an enlarged view of the top view of the structure after each layer is stacked, showing the relative position relationship of each structure. Figure 4 An enlarged view of the superimposed structures on the second dielectric substrate 2 and the third dielectric substrate 4 is shown. Figure 5 An enlarged view of the structure on the first dielectric substrate 1 is shown. Specifically, the representative dimensions of the coplanar waveguide inner conductor 7 on the bottom surface of the second dielectric substrate 2 and the second metal ground layer attached to the third dielectric substrate 4 are W1 = 0.12 mm, W2 = 0.1 mm, W3 = 0.05 mm, W4 = 0.2 mm, W5 = 1.1 mm, and W6 = 1.6 mm. The representative dimensions of the first metal ground layer and coupling window 5 etched on the top surface of the first dielectric substrate 1 are D1 = 0.1 mm, D2 = 0.46 mm, D3 = 1.6 mm, D4 = 0.22 mm, and D3 = 0.8 mm.

[0036] This invention provides a coplanar waveguide-to-stripline transition structure for liquid crystal phase shifters, capable of extracting signals from the liquid crystal phase shifter. Addressing the vertical interconnection issues of liquid crystal phase shifters, this invention proposes a vertically coupled feed structure that balances performance requirements. This structure achieves a coupling form that converts microwave signals from a glass substrate to a PCB substrate, and also converts transmission signals from the coplanar waveguide between the glass interlayers to a stripline. This structure can subsequently be used as a test piece for liquid crystal phase shifters and liquid crystal antennas, connecting antenna units or testing liquid crystal phase shifters. Its practicality is highly worthy of promotion.

[0037] The above disclosure is only a preferred specific embodiment of the present invention. However, the embodiments of the present invention are not limited thereto. Any changes that can be conceived by those skilled in the art should fall within the scope of protection of the present invention.

Claims

1. A coplanar waveguide to stripline transition structure used in liquid crystal phase shifters, characterized in that: include: A first dielectric substrate (1), a second dielectric substrate (2), a liquid crystal layer (3), and a third dielectric substrate (4) are arranged in sequence from top to bottom; in, The upper surface of the first dielectric substrate (1) is provided with a first metal ground layer and a coupling window (5), and the lower surface is provided with a metal conductor strip (6); A wiring layer is provided on the lower surface of the second dielectric substrate (2); A second metal layer is provided on the upper surface of the third dielectric substrate (4); The second dielectric substrate (2) and the third dielectric substrate (4) are glass substrates; The routing layer is a coplanar waveguide inner conductor (7); A slot coupling groove (8) is provided on the second metal layer, and the coplanar waveguide inner conductor (7) and the slot coupling groove (8) constitute a coupling structure of the coplanar waveguide; The first metal ground layer, the first dielectric substrate (1), the metal conductor strip (6), the second dielectric substrate (2), the liquid crystal layer (3) and the second metal ground layer constitute a strip line, and the inner conductor of the strip line is the metal conductor strip (6).

2. The coplanar waveguide to stripline transition structure for liquid crystal phase shifter according to claim 1, characterized in that: The first dielectric substrate (1) is a PCB substrate.

3. The coplanar waveguide to stripline transition structure for liquid crystal phase shifter according to claim 1, characterized in that: The coupling window (5) is in an "H" shape.

4. The coplanar waveguide to stripline transition structure for liquid crystal phase shifter according to claim 1, characterized in that: The thickness of the first dielectric substrate (1) is 0.12-0.13 mm, the thickness of the second dielectric substrate (2) and the third dielectric substrate (4) is 0.28-0.35 mm, the copper cladding thickness of the routing layer and the second metal layer is 0.95-1.5 μm, the thickness of the liquid crystal layer (3) is 5.8-6.2 μm, and the copper cladding thickness of the first metal layer is 0.03-0.04 mm.

5. The coplanar waveguide to stripline transition structure for liquid crystal phase shifter according to claim 4, characterized in that: The thickness of the first dielectric substrate (1) is 0.127 mm, the thickness of the second dielectric substrate (2) and the third dielectric substrate (4) is 0.3 mm, the thickness of the wiring layer and the second metal layer is 1 μm, the thickness of the liquid crystal layer (3) is 6 μm, and the copper coating thickness of the first metal layer is 0.035 mm.

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