A dual-frequency reconfigurable antenna based on electromagnetic bandgap structure for liquid crystal materials

Abstract

The present invention discloses a liquid crystal material dual - band reconfigurable antenna based on an electromagnetic bandgap structure, which comprises an upper - layer dielectric substrate, a middle - layer dielectric substrate and a lower - layer conductive substrate stacked; a microstrip parasitic patch is arranged on the upper surface of the upper - layer dielectric substrate; a slotted rectangular metal patch and a stepped microstrip transmission line are arranged on the lower surface of the upper - layer dielectric substrate, and a groove is formed on the slotted rectangular metal patch to form an S - shape; the stepped microstrip transmission line is led out from one long side of the slotted rectangular metal patch to the edge of the middle - layer dielectric substrate to form a feeder structure; the slotted rectangular metal patch is located in the middle of the orthographic projection area of the microstrip parasitic patch; a liquid crystal groove is hollowed out in the middle of the middle - layer dielectric substrate and filled with liquid crystal; the orthographic projection of the slotted rectangular metal patch is located in the liquid crystal groove; an electromagnetic bandgap structure is arranged at the edge of the middle - layer dielectric substrate and acts on the feeder structure to realize broadband input. This antenna has the capabilities of multi - band wide - frequency reconfiguration and cross - band operation.

Description

Technical Field

[0001] The present invention relates to the technical field of antennas, and in particular, to a liquid crystal material dual - band reconfigurable antenna based on an electromagnetic bandgap structure. Background Art

[0002] With the rapid development of wireless mobile communication technology, users have put forward higher requirements for communication devices. As an essential component in wireless communication terminals, antennas must also adapt to the continuous development of the system, meet different system and standard requirements, and be compatible with more operating frequency bands. However, traditional antennas can only operate in fixed frequency bands and cannot freely switch communication frequency bands according to usage requirements. In response to the above problems, frequency - reconfigurable antennas have emerged. Such antennas can adjust the corresponding operating frequency bands according to changing environments and complex communication systems to ensure the real - time effectiveness of wireless communication.

[0003] Currently, antennas mainly use radio - frequency switch devices to achieve frequency - reconfigurable functions, such as PIN diodes, micro - electro - mechanical systems, etc. The frequency - reconfigurable functions realized by the above - mentioned common radio - frequency switch devices are generally non - covering and non - continuous tuning methods, and cannot cover the blind areas existing between the switching of operating frequency points. In addition, the frequency - reconfigurable functions realized by radio - frequency switch devices will have problems of parasitic effects caused by the integration of electronic components and antennas, resulting in the deterioration of antenna performance, and the electronic components are not conducive to the miniaturization of antennas and circuit integration. In contrast, the introduction of liquid crystal materials, which are electro - controlled materials, can well solve the above problems. The principle of its electro - control characteristics stems from the dielectric anisotropy of liquid crystal materials themselves, so they have good physical properties in microwave, millimeter - wave, and even terahertz bands. Currently, researchers' research on liquid crystal antennas mainly focuses on antenna miniaturization, frequency change range, etc. However, these technical difficulties are more restricted by the properties of liquid crystal materials themselves. Based on the existing technical state and production process of liquid crystal materials, liquid crystal antennas still have the disadvantages and technical difficulties of operating in a single frequency band and having a small frequency change range. Summary of the Invention

[0004] In view of the above - mentioned defects of the prior art, the purpose of the present invention is to provide a liquid crystal antenna to solve the problem that existing antennas can only operate in fixed frequency bands and cannot flexibly switch frequencies according to communication requirements, and to solve problems such as antennas operating in a single frequency band and having a small frequency change range.

[0005] To achieve the above purpose, the present invention provides the following technical solution:

[0006] A liquid crystal material dual - band reconfigurable antenna based on an electromagnetic bandgap structure, comprising an upper dielectric substrate, an intermediate dielectric substrate, and a lower conductive substrate stacked.

[0007] On the upper surface of the upper dielectric substrate, four rectangular microstrip parasitic patches are arranged in two rows and two columns; on the lower surface of the upper dielectric substrate, a slotted rectangular metal patch and a stepped microstrip transmission line are provided. The slotted rectangular metal patch is provided with a pair of T-shaped grooves that are centrosymmetric about the center point of the slotted rectangular metal patch. One end of the transverse groove of the T-shaped groove is an open end, which opens to the wide side of the slotted rectangular metal patch; the longitudinal groove of the T-shaped groove is arranged in a direction away from the center point of the slotted rectangular metal patch; the stepped microstrip transmission line includes a first microstrip transmission line and a second microstrip transmission line, and extends from the midpoint of one long side of the slotted rectangular metal patch to the edge of the intermediate dielectric substrate; the slotted rectangular metal patch is located in the middle of the orthographic projection area of the four rectangular microstrip parasitic patches on the upper surface;

[0008] In the middle of the intermediate dielectric substrate, a liquid crystal cell is hollowed out and filled with liquid crystal; the orthographic projection of the slotted rectangular metal patch is located in the liquid crystal cell; on the edge of the intermediate dielectric substrate, a third microstrip transmission line and two square metal patches located on both sides of the third microstrip transmission line are provided. The second microstrip transmission line and the third microstrip transmission line are edge-connected, and they and the first microstrip transmission line form a feeder structure of the antenna;

[0009] The lower conductive substrate includes a complete conductive metal layer, and the conductive metal layer serves as a ground plane; the two square metal patches are respectively electrically connected to the conductive metal layer of the lower conductive substrate through metallized vias to form an electromagnetic bandgap structure.

[0010] Furthermore, the upper dielectric substrate and the intermediate dielectric substrate are high-frequency substrates made of PTFE composite materials.

[0011] Furthermore, the thicknesses of the upper dielectric substrate and the intermediate dielectric substrate are related to the frequencies of the two resonant frequencies of the liquid crystal material dual-band reconfigurable antenna. Taking the center wavelength of the low-frequency resonant frequency of the antenna as a reference, the thickness of the upper dielectric substrate is about 1 / 25 of the center wavelength; the thickness of the intermediate dielectric substrate is about 1 / 25 of the center wavelength.

[0012] Further, the size of the slotted rectangular metal patch is related to the frequencies of the two resonant frequencies of the liquid crystal material dual-band reconfigurable antenna. Taking the center wavelength of the low-frequency resonant frequency of the antenna as a reference, the length of the slotted rectangular metal patch is about 3 / 5 of the center wavelength, and the width is about 3 / 5 of the center wavelength; the T-shaped groove includes a transverse groove and a longitudinal groove; one end of the transverse groove is the open end of the T-shaped groove, and the other end is the closed end, and the open end of the longitudinal groove is located in the middle of the transverse groove; the groove width of the T-shaped groove is about 1 / 20 of the center wavelength, the length of its transverse groove is about 9 / 25 of the center wavelength, the length of its longitudinal groove is about 2 / 25 of the center wavelength, and the distance from the connection of its longitudinal groove and transverse groove to the closed end of the transverse groove is 3 / 50 of the center wavelength.

[0013] Further, the first microstrip transmission line is narrower than the second microstrip transmission line.

[0014] Further, in a feasible solution, the lower conductive substrate is an aluminum plate or a copper plate.

[0015] Further, in another feasible solution, the lower conductive substrate is a printed circuit board, and the upper surface of the printed circuit board is covered with copper foil.

[0016] The present invention achieves the following technical effects:

[0017] The liquid crystal material dual-band reconfigurable antenna based on the electromagnetic bandgap structure of the present invention has multi-band wide-frequency reconfiguration and the ability to achieve cross-band functions.

[0018] When the liquid crystal material dual-band reconfigurable antenna based on the electromagnetic bandgap structure of the present invention realizes the frequency reconfiguration function, the radiation characteristics within the reconfiguration frequency band range are basically stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the unfolded view of the embodiment of the liquid crystal antenna of the present invention;

[0020] Figure 2 is the side view of the embodiment of the liquid crystal antenna of the present invention;

[0021] Figure 3 is Figure 1 the schematic diagram of the upper surface of the upper dielectric substrate of

[0022] Figure 4 is Figure 1 the schematic diagram of the lower surface of the upper dielectric substrate of

[0023] Figure 5 is Figure 1 the top view of the intermediate dielectric substrate of

[0024] Figure 6 It is a measurement data graph of the antenna return loss varying with voltage in an embodiment of the present invention;

[0025] Figure 7 It is a data graph of the antenna resonance frequency varying with the applied voltage in an embodiment of the present invention;

[0026] Figure 8 It is the radiation pattern of the YOZ plane of the antenna in an embodiment of the present invention;

[0027] Figure 9 It is the radiation pattern of the XOY plane of the antenna in an embodiment of the present invention. Detailed implementation manners

[0028] To further illustrate the embodiments, the present invention provides accompanying drawings. These drawings are part of the disclosure of the present invention, 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, those of ordinary skill in the art should be able to understand other possible implementation manners and the advantages of the present invention. The components in the drawings are not drawn to scale, and similar component symbols are usually used to represent similar components.

[0029] Now, the present invention will be further described in conjunction with the accompanying drawings and specific implementation manners.

[0030] As Figure 1 、 Figure 2 shown, the present invention provides a structural schematic of a liquid crystal material dual - frequency reconfigurable antenna based on an electromagnetic band - gap structure, including an upper - layer dielectric substrate 1, an intermediate - layer dielectric substrate 2, a rectangular groove 3, a lower - layer aluminum plate 5, a microstrip parasitic patch 11, a slotted rectangular metal patch 12, a first microstrip transmission line 6, a second microstrip transmission line 7, a third microstrip transmission line 8, a second via - hole 9, a metallized via - hole 10, a square metal patch 21, etc.

[0031] The upper surface of the upper - layer dielectric substrate 1 is attached with 4 microstrip parasitic patches 11 of the same size, and metallized vias are arranged on the upper - layer microstrip parasitic patch 11. The lower surface of the upper - layer dielectric substrate 1 is attached with a slotted rectangular metal patch 12, a first microstrip transmission line 6 and a second microstrip transmission line 7. The slotted rectangular metal patch 12 is provided with a pair of T - shaped grooves 121 that are centrosymmetric about the center point of the slotted rectangular metal patch 12; the two T - shaped grooves 121 divide the slotted rectangular metal patch 12 into an S - shape; the slotted rectangular metal patch 12 is located within the orthographic projection area of the four microstrip parasitic patches 11.

[0032] A rectangular groove 3 is hollowed out in the middle of the intermediate dielectric substrate 2. The rectangular groove 3 serves as a liquid crystal cavity for accommodating liquid crystal, and the thickness of the rectangular groove 3 is the same as that of the intermediate dielectric substrate 2. The orthographic projection of the slotted rectangular metal patch 12 is located within the rectangular groove 3. A grounded coplanar waveguide structure is provided on the upper surface of the intermediate dielectric substrate 2 near the substrate edge. In this embodiment, the grounded coplanar waveguide structure includes a third microstrip transmission line 8 and a square metal patch 21. The square metal patch 21 and the third microstrip transmission line 8 are coplanar and attached to the upper surface of the intermediate dielectric substrate 2. A pair of square metal patches 21 are symmetrically distributed on both sides of the third microstrip transmission line 8. A metallized via 10 is provided at the center position of the square metal patch 21, and the square metal patch 21 is connected to the lower aluminum plate 5 through the metallized via 10, thereby forming an electromagnetic bandgap structure (or a grounded coplanar waveguide structure).

[0033] Taking the illustrated perspective as an example, mounting holes 4 are provided on both sides of the upper dielectric substrate 1, the intermediate dielectric substrate 2, and the lower aluminum plate 5. The antenna is assembled through the mounting holes 4, so that the upper dielectric substrate 1, the intermediate dielectric substrate 2, and the lower aluminum plate 5 are laminated layer by layer to form an integral body.

[0034] The following gives the specific structural parameters of this embodiment, including: the thicknesses of the upper dielectric substrate 1, the intermediate dielectric substrate 2, and the lower aluminum plate 5 are 0.381 mm, 0.254 mm, and 7 mm respectively. The upper dielectric substrate 1 and the intermediate dielectric substrate 2 are made of high-frequency substrates of PTFE (polytetrafluoroethylene) composite materials such as Taconic TLY(tm)-5 and Rogers RT / Duroid 5880 respectively. The dielectric constants and loss tangent values of the two materials are the same, which are 2.2 and 0.0009 respectively. The two types of high-frequency substrates have different substrate thicknesses, and the upper dielectric substrate 1 and the intermediate dielectric substrate 2 can select suitable types of plates according to different substrate thicknesses. The dielectric constant of the lower aluminum plate 5 is 1. The thicknesses of the upper dielectric substrate 1 and the middle dielectric substrate 2 are related to the frequencies of the two resonant frequencies of the liquid crystal material dual-band reconfigurable antenna. Taking the center wavelength of the low-frequency resonant frequency in the dual-band as a reference, the thickness of the upper dielectric substrate 1 is about 1 / 25 of the center wavelength; the thickness of the intermediate dielectric substrate 2 is about 1 / 25 of the center wavelength. In this embodiment, the center frequency of the low-frequency resonant frequency in the set dual-band is about 32.25 GHz, and the corresponding center wavelength is about 9.3 mm. Based on this, the thicknesses of the upper dielectric substrate 1 and the intermediate dielectric substrate 2 are selected as 0.381 mm and 0.254 mm respectively according to the closest plate thickness.

[0035] The second through-hole 9 vertically penetrates the upper dielectric substrate 1 and is located at the four corner positions of the rectangle of the rectangular groove 3, playing the role of liquid crystal filling and air discharging. The microstrip parasitic patch 11 is located directly above the slotted rectangular metal patch 12 and is distributed around the slotted rectangular metal patch 12.

[0036] The microstrip transmission line is composed of a first microstrip transmission line 6, a second microstrip transmission line 7, and a third microstrip transmission line 8. The edge of the second microstrip transmission line 7 on the lower surface of the upper dielectric substrate 1 coincides with the edge of the third microstrip transmission line 8 of the intermediate dielectric substrate 2 to form a feeder structure.

[0037] The electromagnetic bandgap structure is a high-impedance surface type electromagnetic bandgap structure. Compared with other electromagnetic bandgap structures, the designed electromagnetic bandgap structure is simple, small in size, and easy to implement. The high-impedance surface type electromagnetic bandgap structure is mainly composed of square metal patches, metallized vias, and a metal floor.

[0038] As Figure 3 and Figure 4 shown, the microstrip parasitic patch 11 and the slotted rectangular metal patch 12 are formed on the upper and lower surfaces of the upper dielectric substrate through the PCB etching process, and the thickness is usually 0.035 mm. In this embodiment, the sizes of the various structures are related to the center wavelengths of the two resonant frequencies of the liquid crystal material dual-frequency reconfigurable antenna. In this embodiment, the center frequency of the set low-frequency resonant frequency of the dual frequency is about 32.25 GHz, and the corresponding center wavelength is about 9.3 mm. Based on this, the sizes of each part are designed as follows:

[0039] Microstrip parasitic patch 11; pw = 5.2 mm, pl = 5.5 mm;

[0040] Slotted rectangular metal patch 12: p1 = 5.5 mm, l1 = 5.73 mm;

[0041] T-shaped groove 121: the width of the horizontal groove is 0.5 mm: the length of the horizontal groove is 3.35 mm: the width of the vertical groove is 0.5 mm, and the length of the vertical groove is 0.7 mm; the distance from the connection of the vertical groove and the horizontal groove to the closed end of the horizontal groove is 0.55 mm. Converted into wavelengths, the length p1 of the slotted rectangular metal patch 12 is about 3 / 5 of the center wavelength, and the width l1 is about 3 / 5 of the center wavelength. The groove width of the T-shaped groove 121 is about 1 / 20 of the center wavelength, the length of the horizontal groove is about 9 / 25 of the center wavelength, the length of the vertical groove is about 2 / 25 of the center wavelength, and the distance from the connection of the vertical groove and the horizontal groove to the closed end of the horizontal groove is about 3 / 50 of the center wavelength.

[0042] First microstrip transmission line 6: L2 = 3.135 mm;

[0043] The second microstrip transmission line 7: L3 = 1 mm;

[0044] Rectangular slot 3: p2 = 8 mm, l2 = 8 mm;

[0045] The length of the third microstrip transmission line 8 is 3 mm, and its width is w f = 0.75 mm;

[0046] Square metal patch 21: l3 = 2.35 mm, p3 = 2.35 mm.

[0047] Metallized via hole 10: The diameter is 0.4 mm.

[0048] Assemble the processed plates according to Figure 1 Assemble them together, and use a vector network analyzer and related devices for testing to obtain the measurement data graph of the return loss varying with voltage and the data graph of the resonant frequency varying with the applied voltage, as shown in Figure 5 and Figure 6 respectively. Frequency offsets occur in both the high-frequency band and the low-frequency band of the antenna. Among them, the frequency offset in the low-frequency band is the most obvious. The resonant frequency point moves down from 32.5 GHz to 32 GHz, achieving a frequency offset of 500 MHz. During the entire tuning process, the impedance bandwidth of the antenna basically remains unchanged, and the antenna generally maintains the dual-band characteristic. When the voltage increases from 2 V to 16 V, the reconfiguration frequency range of the antenna is 31 - 33 GHz and 36 - 39 GHz.

[0049] Figure 8 and Figure 9 respectively give the radiation patterns in the YOZ plane and the XOY plane with different dielectric constants. The analysis shows that when the reconfigurable antenna of the present invention realizes the frequency reconfiguration function, the radiation characteristics within the reconfiguration frequency band basically remain stable.

[0050] In summary, the reconfigurable antenna of the present invention has the functions of multi-band wide-frequency reconfiguration and the ability to work across frequency bands.

[0051] Although the present invention is specifically shown and described in combination with the preferred implementation embodiments, those skilled in the art should understand that various changes can be made to the present invention in terms of form and details without departing from the spirit and scope of the present invention defined by the appended claims, and all of them fall within the protection scope of the present invention.

Claims

1. A dual - frequency reconfigurable antenna based on liquid crystal material with electromagnetic band - gap structure, characterized in that, It includes an upper dielectric substrate, an intermediate dielectric substrate, and a lower conductive substrate which are stacked; On the upper surface of the upper dielectric substrate, four rectangular microstrip parasitic patches are arranged in two rows and two columns; on the lower surface of the upper dielectric substrate, a slotted rectangular metal patch and a stepped microstrip transmission line are provided. The slotted rectangular metal patch is provided with a pair of T-shaped grooves that are centrosymmetric about the center point of the slotted rectangular metal patch. One end of the transverse groove of the T-shaped groove is an open end, which opens to the wide side of the slotted rectangular metal patch; the longitudinal groove of the T-shaped groove is arranged along the direction away from the center point of the slotted rectangular metal patch; the stepped microstrip transmission line includes a first microstrip transmission line and a second microstrip transmission line, which extends from the midpoint of one long side of the slotted rectangular metal patch to the edge of the intermediate dielectric substrate; the slotted rectangular metal patch is located in the middle of the orthographic projection area of the four rectangular microstrip parasitic patches on the upper surface; In the middle of the intermediate dielectric substrate, a liquid crystal cell is hollowed out, and the liquid crystal cell is filled with liquid crystal; the orthographic projection of the slotted rectangular metal patch is located in the liquid crystal cell; On the edge of the intermediate dielectric substrate, a third microstrip transmission line and two square metal patches located on both sides of the third microstrip transmission line are provided. The second microstrip transmission line and the third microstrip transmission line are edge-coincidentally connected, and the two and the first microstrip transmission line form a feeder structure of the antenna; The lower conductive substrate includes a complete conductive metal layer, and the conductive metal layer serves as a ground plane; the two square metal patches are respectively electrically connected to the conductive metal layer of the lower conductive substrate through metallized vias to form an electromagnetic bandgap structure; The upper dielectric substrate and the intermediate dielectric substrate are high-frequency substrates made of PTFE composite materials; Taking the center wavelength of the low-frequency resonance frequency point of the antenna as a reference, the thickness of the upper dielectric substrate is selected to be closest to 1 / 25 of the center wavelength; Select the thickness of the intermediate dielectric substrate to be closest to 1 / 25 of the center wavelength; Taking the center wavelength of the low-frequency resonance frequency point of the antenna as a reference, the reference value of the length of the slotted rectangular metal patch is 3 / 5 of the center wavelength, and the reference value of the width is 3 / 5 of the center wavelength; the T-shaped groove includes a transverse groove and a longitudinal groove; one end of the transverse groove is the open end of the T-shaped groove, and the other end is a closed end. The open end of the longitudinal groove is located in the middle of the transverse groove; the reference value of the groove width of the T-shaped groove is 1 / 20 of the center wavelength, the reference value of the length of its transverse groove is 9 / 25 of the center wavelength, the reference value of the length of its longitudinal groove is 2 / 25 of the center wavelength, and the reference value of the distance from the connection of its longitudinal groove and transverse groove to the closed end of the transverse groove is 3 / 50 of the center wavelength.

2. The dual - frequency reconfigurable antenna based on liquid crystal material with electromagnetic band - gap structure according to claim 1, characterized in that, The first microstrip transmission line is narrower than the second microstrip transmission line.

3. The dual - frequency reconfigurable antenna based on liquid crystal material with electromagnetic band - gap structure according to claim 1, characterized in that, The lower conductive substrate is an aluminum plate or a copper plate.

4. The dual - frequency reconfigurable antenna based on liquid crystal material with electromagnetic band - gap structure according to claim 1, characterized in that, The lower conductive substrate is a printed circuit board, and the upper surface of the printed circuit board is covered with copper foil.

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