A liquid crystal phase shifter with continuously adjustable phase
By adopting the liquid crystal electrode and GCPW structure with a concave elliptical ring structure in the liquid crystal phase shifter, the phase continuous adjustability is achieved, solving the problem of complex design and difficult integration of traditional phase shifters, and satisfying the miniaturization and high phase shift and exhibits lower loss and large phase shifts in the millimeter wave band.
Patent Information
- Application Number
- CN202210898226.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-07-28
- Publication Date
- 2024-12-13
- Estimated Expiration
- 2042-07-28
AI Technical Summary
Traditional digital phase shifters cannot achieve continuous adjustability of phases, and with the increase of cascade units, the design is complex and not easy to be miniaturized, and cannot meet the needs of multi-band conversion and dynamic frequency selection.
A liquid crystal phase shifter including an upper dielectric substrate, an inverted microstrip line, an intermediate dielectric substrate and a lower dielectric substrate are designed. The liquid crystal electrode with a concave elliptical ring structure is adopted, and the phase is continuously adjustable through the dielectric constant adjustment of the liquid crystal, and Use the GCPW structure to improve the heat dissipation and mechanical strength of the device.
The phase continuous adjustable of the millimeter wave band is achieved, meeting the needs of miniaturization and high phase shift, while having low insertion loss and phase shift greater than 350°.
Smart Images
Figure CN115275612B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of microwave phase shifters, and in particular to a liquid crystal phase shifter with continuously adjustable phase. Background Art
[0002] As a key component in phased radar systems and phased array antennas, microwave phase shifters play an important role in the entire array system. The essence of a phase shifter is to control the electrical length of the signal transmission path, causing a signal transmission delay, thereby achieving phase delay. Traditional digital phase shifters achieve phase shifting through switches, usually adding phase shifting units and cascading to achieve more phase shift, but the resulting phase is fixed and not continuously adjustable. This design not only fails to meet the miniaturization and integration of equipment, but also becomes more complex as the number of cascaded phase shifting units increases. At the same time, the requirements of communication systems continue to increase, and requirements for multi-band conversion, frequency hopping, dynamic frequency selection, etc. are put forward for the functions of microwave devices. Therefore, tunable passive devices with multiple microwave device functions have emerged.
[0003] At present, the phase shifting principle of the liquid crystal phase shifter is to change the dielectric constant of the liquid crystal material by controlling the external bias, thereby achieving continuous phase shift adjustment. However, the existing liquid crystal phase shifter is large in size and difficult to integrate, and the phase shifting degree is not high. Summary of the invention
[0004] In view of the above-mentioned defects of the prior art, an object of the present invention is to provide a liquid crystal phase shifter with a continuously adjustable phase, the structure of which is easy to realize integration and miniaturization, and has a wide phase shift range.
[0005] To achieve the above-mentioned object, the present invention provides a liquid crystal phase shifter with continuously adjustable phase, comprising an upper dielectric substrate, an inverted microstrip line, an intermediate dielectric substrate, a metal layer and a lower dielectric substrate arranged in a stacked manner; the inverted microstrip line covers the lower surface of the upper dielectric substrate, and the inverted microstrip line structure comprises a concave phase shift unit in the middle and a first microstrip transmission line located at both ends; the center of the intermediate dielectric substrate is hollowed out to form a liquid crystal groove, and the orthographic projection of the concave phase shift unit falls in the liquid crystal groove, and the liquid crystal groove is filled with liquid crystal; the liquid crystal phase shifter is provided with two groups of GCPW structures, and the GCPW structure comprises a second microstrip transmission line located on the upper surface of the intermediate dielectric substrate and metal strip connecting strips located on both sides of the microstrip transmission line, and the metal strip connecting strips are connected through metallized vias penetrating the intermediate dielectric substrate and the metal layer covering the upper surface of the lower dielectric substrate; the second microstrip transmission line and the first microstrip transmission line are partially bonded to form an electrical connection.
[0006] Furthermore, the pattern of the concave phase shifter unit includes an elliptical ring and a pair of concave structures embedded in the elliptical ring, the bottom of the concave structure is fused with the elliptical ring, the protrusion of the concave structure is facing the inner side of the elliptical ring, the pair of concave structures are symmetrically arranged about the long axis of the elliptical ring, and each concave structure is symmetrically arranged about the short axis of the elliptical ring.
[0007] Furthermore, the half-ring length of the elliptical ring is approximately 1.9 to 2.1 times the central wavelength, the ring band width of the elliptical ring is 0.15 to 0.25 times the central wavelength, and the aspect ratio of the elliptical ring is 2.0 to 3.0; the width of the two protrusions of the concave structure is 0.15 to 0.25 times the central wavelength, the spacing between the two protrusions is 0.4 to 0.6 times the central wavelength, and the distance between the protrusions of the two concave structures is 0.15 to 0.25 times the central wavelength.
[0008] Furthermore, the width of the first microstrip transmission line is 0.08 to 0.15 times the central wavelength.
[0009] Furthermore, the liquid crystal cell is a rectangular cell.
[0010] Furthermore, two symmetrically positioned liquid crystal injection holes are disposed on the upper surface of the upper dielectric substrate, and the liquid crystal injection holes are connected to the liquid crystal tank.
[0011] Furthermore, the upper dielectric substrate, the middle dielectric substrate and the lower dielectric substrate are fixed by screws, and the device is packaged by UV curing.
[0012] Furthermore, the upper dielectric substrate, the middle dielectric substrate and the lower dielectric substrate are made of a high-frequency substrate made of PTFE composite material.
[0013] Furthermore, the thickness of the intermediate layer dielectric substrate is 0.01 to 0.07 times.
[0014] Furthermore, the metal layer is formed by metallizing the upper surface of the lower dielectric substrate, or the lower dielectric substrate is a metal plate and the metal layer is the upper surface of the metal plate.
[0015] Furthermore, when the liquid crystal is biased externally and the bias voltage is changed, the relative dielectric constant increases as the bias voltage increases.
[0016] The present invention achieves the following beneficial effects:
[0017] The liquid crystal phase shifter of the present invention realizes continuous adjustable phase in the millimeter wave band by designing an elliptical liquid crystal phase shift unit with a concave structure as a liquid crystal electrode, while meeting the requirements of miniaturization and high phase shift. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1 FIG. 4 is an expanded view of an embodiment of a liquid crystal phase shifter.
[0019] Figure 2 FIG. 4 is a top view of an embodiment of a liquid crystal phase shifter.
[0020] Figure 3 is a side view of an embodiment of a liquid crystal phase shifter.
[0021] Figure 4 FIG. 4 is a structural diagram of a phase shift unit of an embodiment of a liquid crystal phase shifter.
[0022] Figure 5 Insertion loss curve of an embodiment of a liquid crystal phase shifter.
[0023] Figure 6 is the phase shift amount of the embodiment of the liquid crystal phase shifter. DETAILED DESCRIPTION
[0024] To further illustrate the various embodiments, the present invention provides drawings. These drawings are part of the disclosure of the present invention, which are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these contents, a person of ordinary skill in the art should be able to understand other possible implementations and advantages of the present invention. The components in the figures are not drawn to scale, and similar component symbols are generally used to represent similar components.
[0025] The present invention will now be further described with reference to the accompanying drawings and specific implementation methods.
[0026] The present invention provides an embodiment of a liquid crystal phase shifter.
[0027] like Figures 1 to 4 As shown, the concave phase continuously adjustable liquid crystal phase shifter of the present invention comprises, from top to bottom, an upper dielectric substrate 1, an inverted microstrip line, an intermediate dielectric substrate 2, a metal layer 10 and a lower dielectric substrate 3.
[0028] Among them, the inverted microstrip line is covered on the lower surface of the upper dielectric substrate 1, and the inverted microstrip line structure includes a concave phase shift unit 7 in the middle and a first microstrip transmission line 9 at both ends. In this embodiment, the pattern of the concave phase shift unit 7 includes an elliptical ring 71 and a pair of concave structures 72 embedded in the elliptical ring. The bottom of the concave structure 72 is fused with the elliptical ring, and the protrusion of the concave structure 72 faces the inner side of the elliptical ring. This pair of concave structures 72 are symmetrically arranged about the long axis x of the elliptical ring, and each concave structure 72 is symmetrically arranged about the short axis y of the elliptical ring. The microstrip transmission line 9 is arranged along the long axis x of the elliptical ring.
[0029] The center of the intermediate dielectric substrate 2 is hollowed out to form a liquid crystal tank 4, and the depth of the liquid crystal tank 4 is the thickness of the intermediate dielectric substrate 2. In this embodiment, the liquid crystal tank 4 is a rectangular structure, and the concave phase shift unit 7 is located above the liquid crystal tank 4. The pattern of the concave phase shift unit 7 is smaller than the size of the liquid crystal tank 4, and its positive projection falls within the liquid crystal tank 4; through the cooperation of the upper dielectric substrate 1, the intermediate dielectric substrate 2 and the metal layer 10, the liquid crystal tank 4 forms a closed cavity. Two liquid crystal injection holes 6 connected to the liquid crystal tank 4 are opened at symmetrical positions of the upper dielectric substrate 1 to ensure that gas can be discharged when filling the liquid crystal.
[0030] The liquid crystal phase shifter is provided with a GCPW structure 5 connected to the first microstrip transmission line 9. The GCPW structure 5 includes a second microstrip transmission line 51 located on the upper surface of the intermediate dielectric substrate 2 and a metal strip connection belt 52 located on both sides of the microstrip transmission line. The second microstrip transmission line 51 and the first microstrip transmission line 9 are stacked and electrically connected. The metal strip connection belt 52 is connected to the metal layer 10 on the upper surface of the lower dielectric substrate 3 through a metallized via 8 that penetrates the intermediate dielectric substrate 2, and serves as a metal ground. GCPW is called Grounded CoPlanar Waveguide. The two GCPW structures 5 serve as the feeder input end and the feeder output end of the liquid crystal phase shifter, respectively. At the same time, the GCPW structure 5 is conducive to the heat dissipation of the device, improves the mechanical strength of the structure, and plays the role of a heat sink for the device circuit. Compared with the microstrip line, the GCPW structure can more conveniently adjust the characteristic impedance of the transmission line by adjusting the width W of the center conductor (i.e., the microstrip line) and the gap size between the center conductor and the strip connection belt. In addition, the metal ground on both sides of the GCPW structure also facilitates mutual shielding between RF circuit modules and reduces unnecessary parasitics.
[0031] In this embodiment, the thickness of the upper dielectric substrate 1 and the lower dielectric substrate 3 are both 0.254 mm, and the thickness of the middle dielectric substrate 2 is 0.127 mm. The upper dielectric substrate 1, the middle dielectric substrate 2, and the lower dielectric substrate 3 are made of glass microfiber reinforced PTFE composite materials such as RogersRT / Duroid 5880, which are specially designed for precision stripline and microwave circuit applications. Its typical relative dielectric constant is 2.2 and its loss tangent is 0.0009. The three-layer dielectric substrate is provided with screw holes 11, which are screwed during assembly. After assembly, glue UV curing glue is used for device packaging to prevent liquid crystal leakage.
[0032] In this embodiment, a bias voltage is applied to the liquid crystal through the concave phase shift unit 7. When the liquid crystal is not biased, the relative dielectric constant ε r =2.74, when bias is applied and bias voltage is changed, relative dielectric constant ε r The relative dielectric constant ε varies from 2.75 to 5.44.r The thickness of the liquid crystal is determined by the thickness of the intermediate dielectric substrate 2. Preferably, the thickness of the intermediate dielectric substrate is 0.01 to 0.07 times the central wavelength, and the optional substrate thickness includes 0.127 mm, 0.254 mm, 0.508 mm, etc.
[0033] In this embodiment, the central frequency of the liquid crystal phase shifter is 39.0 GHz, and the central wavelength is about 7.7 mm. Figure 1 , Figure 2 , the length of the upper dielectric substrate 1 is 20 mm, the width is 13.5 mm, and the diameter of the liquid crystal injection hole 6 is 1 mm. The length L3 and width W1 of the two protrusions of the concave structure 72 of the concave phase shift unit 7 are W1=1.4 mm and L3=1.5 mm respectively, wherein the width W1 is approximately 0.15 to 0.25 times of the central wavelength, the spacing L2 of the two protrusions in the concave structure 72 is 4 mm, which is approximately 0.5 times of the central wavelength, and can be controlled to be 0.4 to 0.6 times of the central wavelength, the length La of the inner ring of the ellipse and the length Lb of the outer ring are La=12.65 mm and Lb=14.4 mm respectively, the aspect ratio of the ellipse is 2.0 to 3.0, the length of half of the ellipse is approximately 15 mm to 16 mm, which is approximately twice the central wavelength, such as being set at 1.9 to 2.1 times of the central wavelength; the band width of the ellipse is 0.15 to 0.25 times of the central wavelength. The distance between the protrusions of the two concave structures 72 is about 1.5 mm, which is about 0.15 to 0.25 times the central wavelength. The width W of the first microstrip transmission line 9 connecting the elliptical ring 71 is 0.8 mm, which is 0.08 to 0.15 times the central wavelength. The intermediate dielectric substrate 2 and the lower dielectric substrate 3 have the same size, both of which are 28 mm long and 13.5 mm wide. The liquid crystal tank 4 is 17 mm long and 9 mm wide. The diameter of the metallized vias 8 on the metal strip connecting belt 52 (metal ground) in the GCPW structure 5 is 1 mm. The inverted transmission line on the lower surface of the upper dielectric substrate 1, the GCPW structure 5 on the intermediate dielectric substrate 2, the metal layer 10 on the upper surface of the lower dielectric substrate 3, the liquid crystal tank 4, the screw hole 11 and other slot parts are all realized by printed circuit board technology.
[0034] The dielectric substrate Rogers RT / Duroid 5880 is selected as the single-sided high-frequency printed circuit board and processed into Figure 1 The structure shown in Figure 1 Assemble them together, inject liquid crystal, and solidify the package. The packaged liquid crystal phase shifter is tested on a vector network analyzer, and the obtained insertion loss and phase shift change curves are as follows: Figure 5 , Figure 6 As shown. Figure 5 , Figure 6It can be seen that within the frequency range of 38.6 GHz to 39.5 GHz, the reflection coefficient is less than -10 dB and has a phase shift greater than 350°, and the insertion loss is less than 1.1 dB; the maximum phase shift is about 356° at the resonance frequency of 39.06 GHz. It can be seen that the liquid crystal phase shifter provided in this embodiment has a continuously adjustable phase, has a low insertion loss, and can obtain a large phase shift.
[0035] This embodiment has the following beneficial effects:
[0036] The liquid crystal phase shifter of the present invention realizes continuous adjustable phase in the millimeter wave band by designing an elliptical liquid crystal phase shift unit with a concave structure as a liquid crystal electrode, while meeting the requirements of miniaturization and high phase shift.
[0037] Although the present invention has been specifically shown and described in conjunction with the preferred embodiments, it should be understood by those skilled in the art that various changes may be made to the present invention in form and details without departing from the spirit and scope of the present invention as defined by the appended claims, all of which are within the scope of protection of the present invention.
Claims
1. A liquid crystal phase shifter with continuously adjustable phase, It is characterized in that It comprises an upper dielectric substrate, an inverted microstrip line, an intermediate dielectric substrate, a metal layer and a lower dielectric substrate which are stacked; the inverted microstrip line is covered on the lower surface of the upper dielectric substrate, and the inverted microstrip line structure comprises a concave phase shift unit in the middle and first microstrip transmission lines at both ends; The center of the intermediate dielectric substrate is hollowed out to form a liquid crystal groove, the orthographic projection of the concave phase shift unit falls in the liquid crystal groove, and the liquid crystal groove is filled with liquid crystal; the liquid crystal phase shifter is provided with two groups of GCPW structures, the GCPW structure includes a second microstrip transmission line located on the upper surface of the intermediate dielectric substrate and metal strip connecting belts located on both sides of the microstrip transmission line, the metal strip connecting belts are connected through metallized vias penetrating the intermediate dielectric substrate and the metal layer covering the upper surface of the lower dielectric substrate; the second microstrip transmission line and the first microstrip transmission line are partially bonded to form an electrical connection; The pattern of the concave phase shifter unit includes an elliptical ring and a pair of concave structures embedded in the elliptical ring. The bottom of the concave structure is fused with the elliptical ring, and the protrusion of the concave structure faces the inner side of the elliptical ring. The pair of concave structures are symmetrically arranged about the long axis of the elliptical ring, and each concave structure is symmetrically arranged about the short axis of the elliptical ring.
2. The liquid crystal phase shifter according to claim 1, It is characterized in that The half-ring length of the elliptical ring is 1.9 to 2.1 times the central wavelength, the ring band width of the elliptical ring is 0.15 to 0.25 times the central wavelength, and the aspect ratio of the elliptical ring is 2.0 to 3.0; the width of the two protrusions of the concave structure is 0.15 to 0.25 times the central wavelength, the spacing between the two protrusions is 0.4 to 0.6 times the central wavelength, and the distance between the protrusions of the two concave structures is 0.15 to 0.25 times the central wavelength.
3. The liquid crystal phase shifter according to claim 1, It is characterized in that The width of the first microstrip transmission line is 0.08 to 0.15 times of the central wavelength.
4. The liquid crystal phase shifter according to claim 1, It is characterized in that Two symmetrically positioned liquid crystal injection holes are arranged on the upper surface of the upper dielectric substrate, and the liquid crystal injection holes are communicated with the liquid crystal tank.
5. The liquid crystal phase shifter according to claim 1, It is characterized in that The upper dielectric substrate, the middle dielectric substrate and the lower dielectric substrate are fixed by screws, and the device is packaged by UV curing.
6. The liquid crystal phase shifter according to claim 1, It is characterized in that The upper dielectric substrate, the middle dielectric substrate and the lower dielectric substrate are made of a high-frequency substrate made of PTFE composite material.
7. The liquid crystal phase shifter according to claim 6, It is characterized in that The thickness of the intermediate layer dielectric substrate is 0.01 to 0.07 times of the central wavelength.
8. The liquid crystal phase shifter according to claim 1, Features: The metal layer is formed by metallizing the upper surface of the lower dielectric substrate, or the lower dielectric substrate is a metal plate and the metal layer is the upper surface of the metal plate.
9. The liquid crystal phase shifter according to claim 1, It is characterized in that When the liquid crystal is biased externally and the bias voltage is changed, the relative dielectric constant increases as the bias voltage increases.