A MEMS switch regulated terahertz dual-patch type metasurface antenna unit

Abstract

The application discloses a MEMS switch regulated terahertz double-patch type metasurface antenna unit, and belongs to the field of terahertz wireless communication equipment. The unit comprises two layers of quartz glass dielectric substrates; the lower surface of the lower layer of quartz glass dielectric substrate is provided with a bias circuit, the lower surface of the upper layer of quartz glass dielectric substrate is provided with a metal ground, and the upper surface is provided with a 1-Bit radiation unit. The 1-Bit radiation unit is composed of a double-patch type microstrip patch and a MEMS switch located in the middle of the double patch; the double-patch type microstrip patch is left-right symmetrical, the middle connecting line is provided with an opening, and each of the left and right patches is provided with a rectangular branch on the outer side; different working states of the MEMS switch change the surface current mode of the double-patch type microstrip patch, so that the 180° reflection phase difference of the radiation unit is realized. The metasurface antenna unit has the advantages of low profile, simple structure and high integration, and realizes terahertz high-gain, narrow-beam beam forming and beam tracking.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of terahertz wireless communication devices, and particularly relates to a MEMS switch regulated terahertz double-patch type metasurface antenna unit, which can be applied to a terahertz reflection type metasurface array antenna. BACKGROUND

[0002] A metasurface is a two-dimensional planar form of metamaterials, has the advantages of low profile, high integration, easy processing and the like, and its theoretical basis is the generalized Snell's law proposed by the Capasso professor group of Harvard University in 2011, abnormal reflection and abnormal refraction are achieved by introducing phase jumps on the interface, and the metasurface can be applied to fields such as optical lenses, electromagnetic cloaking materials and beam forming antennas.

[0003] A metasurface antenna is usually formed by periodically arranging many subwavelength artificial electromagnetic structure units, the physical structure characteristics of the units are adjusted to change the equivalent circuit parameters of the surface, and then the phase state of the transmitted / reflected electromagnetic wave is regulated, so that beam scanning is achieved. In recent years, researchers have been committed to studying various regulation methods to obtain flexible and tunable metasurface antennas, so as to freely and dynamically manipulate electromagnetic waves.

[0004] At present, metasurface antennas can be divided into two categories according to different regulation methods: the first category is a metasurface antenna based on special materials, such as graphene, liquid crystal materials, phase change materials and the like. The application CN115275588B proposes a terahertz metasurface antenna based on graphene material, which uses the characteristic that the surface impedance of the graphene material changes with the electric potential, cooperates with a metal pattern layer and a circular ring gap, and realizes a wideband reconfigurable intelligent metasurface antenna unit with a center frequency of 95 GHz and a center frequency of 300 GHz. In 2025, Liudongna et al. proposed a metasurface antenna based on liquid crystal materials, which realizes regulation effect by inducing liquid crystal molecules to rearrange through an external electric field. The metasurface antenna based on special materials usually has large insertion loss due to the characteristics of the materials themselves. The second category is a metasurface antenna based on various adjustable switches. The application CN202510085592.X proposes a terahertz transmission metasurface unit based on a Schottky varactor diode, and the application CN202210787971.X proposes a metasurface antenna based on a PIN switch, both of which change the working state of the switch through a direct current bias voltage, and then regulate the equivalent circuit parameters of the metasurface unit to realize beam control. However, the traditional varactor diode and PIN switch have large size, high loss and limited phase regulation range, and are not suitable for metasurface antenna units in the terahertz frequency band. SUMMARY

[0005] In view of the problems of high loss and limited phase control faced by the terahertz metasurface antenna, the application provides a MEMS switch controlled terahertz double-patch metasurface antenna unit, which has the advantages of low profile, simple structure and high integration, and can be applied to a terahertz reflective metasurface antenna array to realize terahertz high-gain, narrow-beam beamforming and beam tracking.

[0006] To achieve the above effects, the technical scheme adopted by the application is as follows:

[0007] A MEMS switch controlled terahertz double-patch metasurface antenna unit, comprising upper and lower quartz glass dielectric substrates; the lower surface of the lower quartz glass dielectric substrate is provided with a bias circuit; the lower surface of the upper quartz glass dielectric substrate is provided with a metal ground, and the upper surface of the upper quartz glass dielectric substrate is provided with a 1-Bit radiation unit; the 1-Bit radiation unit is composed of a double-patch microstrip patch and a MEMS switch located at the middle position of the double-patch microstrip patch.

[0008] The double-patch microstrip patch comprises two rectangular patches as the main body, the two rectangular patches are symmetrically arranged, and the outer side end corners of each rectangular patch are provided with rectangular defects; on the same rectangular patch, the patch area between the two opposite rectangular defects is a rectangular branch.

[0009] A metal connecting line is arranged between the two rectangular patches, the middle position of the metal connecting line is an open structure, and the metal fixed beam of the MEMS switch is located directly above the open structure.

[0010] Further, the MEMS switch comprises a metal fixed beam and a metal contact; the metal fixed beam is a rectangular structure, the middle of the metal fixed beam is a conduction part, the two sides are pull-down parts, a plurality of circular through holes are arranged on the metal fixed beam for releasing the sacrificial layer; the metal contact is located on the lower surface of the conduction part of the metal fixed beam.

[0011] The upper surface of the upper quartz glass dielectric substrate is further provided with two metal driving electrodes and two metal anchor points, and the two metal driving electrodes and the two metal anchor points are located between the two rectangular patches; the metal driving electrodes are located on the two sides of the metal connecting line, and the metal anchor points are located on the outer side of the corresponding metal driving electrodes; the two ends of the metal fixed beam are respectively arranged on the top of the two metal anchor points, and the metal contact thereof is directly opposite the open structure of the metal connecting line; the metal driving electrode is located directly below the pull-down part of the metal fixed beam, and a silicon nitride dielectric layer is arranged on the upper surface of the metal driving electrode.

[0012] Further, the lower surface of each metal driving electrode is connected with the bias circuit through a corresponding TGV through hole, and the TGV through hole penetrates through the two quartz glass dielectric substrates and has no contact with the metal ground.

[0013] Compared with the prior art, the application has the following advantages:

[0014] The 1-Bit (180°) radiation unit designed by the application takes a double-plate type microstrip patch as the main body, the two rectangular patches of the main body are left-right symmetrical, and a rectangular branch is arranged in each outer corner of the rectangular patch, so as to realize phase control in a larger range; in view of the high loss problem of the terahertz super surface antenna, the MEMS control switch is designed between the two rectangular patches, the metal electrode of the MEMS control switch is in communication with the bias circuit through the TGV through hole, and the metal electrode is used for controlling the MEMS switch to be in different working states; compared with the traditional phase change material, the variable capacitance diode and the PIN switch, the MEMS switch has lower insertion loss and higher integration. The super surface antenna unit changes the surface current mode of the double-plate type microstrip patch by using different working states of the MEMS switch, so as to realize the 180° (1-Bit) reflection phase difference of the radiation unit. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical scheme of the application, the drawings used in the embodiments are briefly described below.

[0016] Figure 1 It is an overall structure explosion diagram of the application;

[0017] Figure 2 It is a top view of the 1-Bit radiation unit in the application;

[0018] Figure 3 It is a top view of the double-plate type microstrip patch in the application;

[0019] Figure 4 It is a top view of the metal fixed beam in the application;

[0020] Figure 5 It is a schematic diagram of the MEMS control switch in the application;

[0021] Figure 6 It is a relative position diagram of the double-plate type microstrip patch, the anchor area of the MEMS switch and the metal driving electrode in the application;

[0022] Figure 7 It is a sectional view of the terahertz super surface unit in the application;

[0023] Figure 8 It is a top view of the metal ground in the application;

[0024] Figure 9 It is a schematic diagram of the bias circuit in the application;

[0025] Figure 10 It is a reflection phase diagram of the super surface unit in the MEMS switch open / closed state;

[0026] Figure 11 Reflection amplitude diagram of the metasurface unit in the open / closed state of the MEMS switch. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to understand the technical content of the present application, the content of the present application is further described below in combination with the drawings.

[0028] The terahertz metasurface antenna unit comprises two layers of quartz glass dielectric substrates 1, an upper quartz glass dielectric substrate and a lower quartz glass dielectric substrate. The lower surface of the lower quartz glass dielectric substrate is provided with a bias circuit 8, the lower surface of the upper quartz glass dielectric substrate is provided with a metal ground 3, and the upper surface is provided with a 1-Bit radiation unit.

[0029] The 1-Bit radiation unit is composed of a double-patch microstrip patch and a MEMS switch 5 located in the middle of the double-patch microstrip patch; the double-patch microstrip patch is symmetrical left and right, the middle metal connecting line 10 is provided with an opening structure, the two rectangular patches 4 of the double-patch microstrip patch are symmetrical left and right, and the outer side end corners of each rectangular patch 4 are provided with rectangular defects; on the same rectangular patch 4, the patch area between the two opposite rectangular defects is a rectangular branch 9; the MEMS switch 5 is a three-dimensional structure, from top to bottom in turn is a metal fixed beam 11, a silicon nitride dielectric layer 6, and a metal driving electrode 7.

[0030] The bottom of the metal driving electrode 7 is communicated with the bias circuit 8 through the TGV through hole 2, which is used to control the MEMS switch 5 to be in different working states. By utilizing the different working states of the MEMS switch 5, the surface current mode of the double-patch microstrip patch is changed, so as to realize the 180° (1-Bit) reflection phase difference of the radiation unit.

[0031] The terahertz double-patch metasurface antenna unit controlled by the MEMS switch 5 is realized by micro-nano metal surface processing technology, and the specific processing steps are as follows:

[0032] Step 1: The quartz substrate with a thickness of 400 μm is surface cleaned;

[0033] Step 2: Sputter seed layer of double-patch microstrip patch and metal driving electrode 7, then electroplating thickening, thickness 1 μm;

[0034] Step 3: Grow SiN dielectric layer at the capacitor position by PECVD system, thickness 0.1 μm;

[0035] Step 4: Spin-coat polyimide sacrificial layer, thickness 2 μm;

[0036] Step 5: Etch the anchor structure on the sacrificial layer, then sputter the seed layer and electroplating thickening, anchor height 2 μm;

[0037] Step 6: Fabricate the metal clamped beam 5 by sputtering seed layer and electroplating thickening, thickness 1 μm;

[0038] Step 7: Release the sacrificial layer, get the suspended MEMS clamped beam.

[0039] The following is a more specific embodiment:

[0040] As Figure 1 The exploded view of the THz dual-patch type metasurface unit controlled by MEMS switch is shown, including two layers of quartz glass dielectric substrate 1, TGV via 2 penetrating through the two layers of substrate, metal ground 3 located in the middle of the two layers of quartz glass dielectric substrate 1, dual-patch microstrip patch located on the upper surface of the upper layer of quartz glass dielectric substrate, MEMS switch 5, silicon nitride dielectric layer 6 of MEMS switch 5, metal driving electrode 7 of MEMS switch 5, bias circuit 8 located on the lower surface of the lower layer of quartz glass dielectric substrate.

[0041] The dielectric constant of the quartz glass dielectric substrate 1 is 3.78, and the thickness of the substrate is 400 μm.

[0042] Figure 2 The top view of the 1-Bit radiation unit is shown, including dual-patch microstrip patch and MEMS switch 5, which is arranged in the middle of the two rectangular patches 4.

[0043] Figure 3 The top view of the dual-patch microstrip patch is shown. The center frequency of the metasurface unit in this example is 300 GHz, and according to the working frequency, the size of each rectangular patch 4 of the dual-patch microstrip patch can be calculated as L 1=0.3mm, W 1=0.1mm. In order to improve the phase control range of the unit, the size of the rectangular branch 9 between the two rectangular defects on the same rectangular patch 4 is L 2=0.13mm, W 2=0.035mm. The left and right rectangular patches 4 are connected by a metal connecting line 10, and the size of the metal connecting line 10 is L 3=0.04mm, W 3=0.06mm. Under working condition, there is a surface current flowing from one side patch to the other side patch, which breaks the metal connecting line 10 in the middle. Subsequently, the on / off state of the metal clamped beam 11 of the MEMS switch 5 is controlled, thereby changing the flow direction of the surface current and realizing a 180° phase difference of the reflected electromagnetic wave.

[0044] The structure of the MEMS switch is referred to Figure 4 and Figure 5, it includes metal fixed beam 11, metal anchor point 12, metal driving electrode 7, silicon nitride dielectric layer 6, the materials of metal fixed beam 11, metal contact 13, metal anchor point 12 and metal driving electrode 6 are gold Au. Metal fixed beam 11 is designed as a crane leg structure, refer to Figure 4 , its main body is in the form of a rectangle, and the lower pull part on both sides has a rectangular hollow and a circular through hole, wherein the area where the circular through hole is located is opposite to the metal driving electrode 7, the purpose is to reduce the elastic coefficient of the MEMS switch 5, and further reduce the driving voltage value; the purpose is to facilitate the release of the sacrificial layer during processing, and also can further reduce the driving voltage value.

[0045] The size of the metal fixed beam 11 is: L 4=0.3mm, W 4=0.5mm, L 5=0.08mm, W 5=0.02mm, L 6=0.04mm, W 6=0.015mm, R =0.015mm.

[0046] Figure 6 The relative position diagram of the double-chip microstrip patch and the anchor area of the MEMS switch and the metal driving electrode is shown, the size of the metal driving electrode 7 is L 7=0.04mm, W 7=0.05mm, the size of the metal anchor point 12 is L 8=0.02mm, W 8=0.05mm.

[0047] The metal driving electrode 7 of the MEMS switch 5 is connected with the bias circuit 8 on the lower surface through the TGV through hole 2, and is driven by the electrostatic force, the metal fixed beam 11 of the MEMS switch 5 is located at different heights, thereby changing the surface current distribution between the double-chip microstrip patches, and realizing the 180° (1-Bit) reflection phase difference of the radiation unit. Figure 7 The cross-sectional view of the terahertz super surface unit is shown, the TGV through hole 2 penetrates through the two layers of quartz glass substrates and the metal ground 3, and is connected with the metal driving electrode 7 and the bias circuit 8 respectively.

[0048] A circular groove is opened on the metal ground 3 for passing through the TGV through hole 2, as shown in Figure 8 .

[0049] The bias circuit 8 is located on the lower surface of the bottom quartz glass substrate, and is used to provide a direct current driving voltage for the MEMS switch 5, as shown in Figure 9 , the through hole at the end of the bias circuit 8 is connected with the TGV through hole 2, and the other end can be connected to the control circuit board through the flat cable.

[0050] The transmission characteristic curve of the metasurface unit is obtained using 3D simulation software:

[0051] like Figure 10 Figure 2 shows the phase difference of the reflected electromagnetic wave from the metasurface unit when the MEMS switch is open and closed. At a center frequency of 300 GHz, the phase of the reflected electromagnetic wave is -23.5° when the MEMS switch 5 is open, and -214.2° when the MEMS switch 5 is closed, resulting in a phase difference of 190.7°. Within the frequency range of 300-310 GHz, the phase difference is 180°±10°.

[0052] like Figure 11 The figure shows the amplitude of the reflected electromagnetic wave of the metasurface unit when the MEMS switch is open and closed. At the center frequency of 300 GHz, the amplitude of the reflected electromagnetic wave is -0.9 dB when the MEMS switch 5 is open, and the amplitude of the reflected electromagnetic wave is -0.23 dB when the MEMS switch 5 is closed, which indicates that the metasurface unit has lower loss and higher radiation efficiency.

[0053] The above-mentioned specific implementation can be locally adjusted in different ways by those skilled in the art without departing from the principles and purpose of the present invention, such as adjusting the size of the radiating microstrip patch according to the working frequency band. The scope of protection of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. All implementation plans within its scope shall be subject to the constraints of the present invention.

Claims

1. A terahertz double-piece metasurface antenna unit controlled by a MEMS switch, comprising an upper and a lower quartz glass dielectric substrate (1); characterized in that: A bias circuit (8) is provided on the lower surface of the lower quartz glass dielectric substrate; a metal ground (3) is provided on the lower surface of the upper quartz glass dielectric substrate, and a 1-bit radiation unit is provided on the upper surface of the upper quartz glass dielectric substrate; the 1-bit radiation unit is composed of a double-chip microstrip patch and a MEMS switch (5) located in the middle of the double-chip microstrip patch; The double-piece microstrip patch includes two rectangular patches (4) as a main body, the two rectangular patches (4) are symmetrically arranged, and the outer end corners of each rectangular patch (4) are provided with a rectangular defect; on the same rectangular patch (4), the patch area between the two opposite rectangular defects is a rectangular branch (9); A metal connecting line (10) is provided between the two rectangular patches, the middle position of the metal connecting line (10) is a disconnected opening structure, and the metal fixed support beam (11) of the MEMS switch (5) is located directly above the opening structure; The MEMS switch (5) comprises a metal fixing beam (11) and a metal contact (13); the metal fixing beam (11) is a rectangular structure, the middle of the metal fixing beam (11) is a conducting portion, and both sides are pull-down portions, and the metal fixing beam (11) is provided with a plurality of circular through holes for releasing the sacrificial layer; the metal contact (13) is located on the lower surface of the conducting portion of the metal fixing beam (11); Two metal drive electrodes (7) and two metal anchor points (12) are further provided on the upper surface of the upper quartz glass dielectric substrate, and the two metal drive electrodes (7) and the two metal anchor points (12) are located between the two rectangular patches (4); the metal drive electrodes (7) are respectively located on both sides of the metal connecting line (10), and the metal anchor points (12) are located outside the corresponding metal drive electrodes (7); the two ends of the metal fixed support beam (11) are respectively placed on the top of the two metal anchor points (12), and its metal contact (13) is directly opposite to the opening structure of the metal connecting line (10); the metal drive electrode (7) is located directly below the pull-down portion of the metal fixed support beam (11), and a silicon nitride dielectric layer (6) is provided on its upper surface.

2. The terahertz dual-chip metasurface antenna unit controlled by a MEMS switch according to claim 1, characterized in that: The lower surface of each metal driving electrode (7) is connected to the bias circuit (8) through a corresponding TGV through hole (2), and the TGV through hole (2) passes through two layers of quartz glass dielectric substrate (1) and has no contact with the metal ground (3).

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