Terahertz dual-sheet metasurface antenna unit regulated and controlled by MEMS switch

Abstract

The invention discloses a terahertz dual-sheet metasurface antenna unit regulated and controlled by an MEMS switch, and belongs to the field of terahertz wireless communication equipment. The filter comprises two layers of 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-sheet microstrip patch and an MEMS switch located between the double-sheet microstrip patch. An opening is formed in a middle connecting line, and a rectangular branch knot is arranged on the outer side of each of the left patch and the right patch; different working states of the MEMS switch change the surface current mode of the biplate microstrip patch, so that the 180-degree reflection phase difference of the radiation unit is realized. The metasurface antenna unit has the advantages of being low in profile, simple in structure and high in integration level, and beam forming and beam tracking of terahertz high gain and narrow beams are achieved.

Description

Technical Field

[0001] The present invention belongs to the field of terahertz wireless communication equipment, specifically a terahertz double-piece metasurface antenna unit controlled by a MEMS switch, which can be applied to a terahertz reflective metasurface array antenna. Background Art

[0002] Meta-surface is a two-dimensional planar form of metamaterial with advantages such as low profile, high integration, and easy processing. Its theoretical basis is the generalized Snell's law proposed by Professor Capasso's research group at Harvard University in 2011. It achieves anomalous reflection and refraction by introducing phase mutations on the interface, and can be applied to optical lenses, electromagnetic stealth materials, beamforming antennas and other fields.

[0003] Metasurface antennas are typically composed of a periodic arrangement of many subwavelength artificial electromagnetic structural units. By adjusting the physical structural characteristics of these units, the equivalent circuit parameters of the surface are altered, thereby controlling the phase state of the transmitted / reflected electromagnetic waves and achieving beam scanning. In recent years, researchers have been committed to studying various control methods to obtain flexible and tunable metasurface antennas, thereby freely and dynamically manipulating electromagnetic waves.

[0004] At present, metasurface antennas can be divided into two categories according to the different control methods: the first category is metasurface antennas based on special materials, such as graphene, liquid crystal materials, phase change materials, etc. Invention CN115275588B proposes a terahertz metasurface antenna based on graphene materials, which utilizes the characteristics of the surface impedance of graphene materials changing with electric potential, and cooperates with metal pattern layers and circular ring gaps to realize broadband reconfigurable intelligent metasurface antenna units with center frequencies of 95GHz and 300GHz. In 2025, Liu Dongna and others proposed a metasurface antenna based on liquid crystal materials, which achieves a control effect by inducing the rearrangement of liquid crystal molecules through an external electric field. Metasurface antennas based on special materials usually have large insertion losses due to the characteristics of the material itself. The second category is metasurface antennas based on various adjustable switches. Invention CN202510085592.X proposes a terahertz-transmitting metasurface unit based on a Schottky varactor diode, and invention CN202210787971.X proposes a metasurface antenna based on a PIN switch. Both utilize a DC bias voltage to change the switch's operating state, thereby regulating the metasurface unit's equivalent circuit parameters and achieving beam steering. However, traditional varactor diodes and PIN switches are large, have high losses, and have a limited phase control range, making them unsuitable for metasurface antenna units operating in the terahertz band. Summary of the Invention

[0005] In response to the high loss and limited phase control problems faced by terahertz metasurface antennas, the present invention proposes a terahertz double-piece metasurface antenna unit controlled by MEMS switches. It has the advantages of low profile, simple structure and high integration. It can be applied to terahertz reflective metasurface antenna arrays to achieve terahertz high-gain, narrow beam beam forming and beam tracking.

[0006] In order to achieve the above effects, the technical solutions adopted by the present invention are specifically as follows: A terahertz double-chip metasurface antenna unit controlled by a MEMS switch comprises upper and lower quartz glass dielectric substrates; a bias circuit is provided on the lower surface of the lower quartz glass dielectric substrate; a metal ground is provided on the lower surface of the upper quartz glass dielectric substrate, and a 1-bit radiating unit is provided on the upper surface of the upper quartz glass dielectric substrate; the 1-bit radiating unit comprises a double-chip microstrip patch and a MEMS switch located between the double-chip microstrip patch; The double-piece microstrip patch includes two rectangular patches as the main body, the two rectangular patches are symmetrically arranged, and the outer end corners of each rectangular patch are provided with a rectangular defect; on the same rectangular patch, the patch area between the two opposite rectangular defects is a rectangular branch; A metal connecting line is provided between the two rectangular patches. The middle position of the metal connecting line is a disconnected opening structure. The metal fixing beam of the MEMS switch is located directly above the opening structure.

[0007] Furthermore, the MEMS switch includes a metal clamping beam and metal contacts; the metal clamping beam is a rectangular structure, the middle of the metal clamping beam is a conductive portion, and the two sides are pull-down portions. The metal clamping beam is provided with a plurality of circular through holes for releasing the sacrificial layer; the metal contacts are located on the lower surface of the conductive portion of the metal clamping beam; Two metal drive electrodes and two metal anchor points are also provided on the upper surface of the upper quartz glass dielectric substrate, and the two metal drive electrodes and the two metal anchor points are located between the two rectangular patches; the metal drive electrodes are respectively located on both sides of the metal connecting line, and the metal anchor points are located on the outside of the corresponding metal drive electrodes; the two ends of the metal clamping beam are respectively placed on top of the two metal anchor points, and their metal contacts are directly opposite the opening structure of the metal connecting line; the metal drive electrode is located directly below the pull-down portion of the metal clamping beam, and its upper surface is provided with a silicon nitride dielectric layer.

[0008] Furthermore, the lower surface of each metal driving electrode is connected to the bias circuit through a corresponding TGV through-hole. The TGV through-hole passes through two layers of quartz glass dielectric substrates and has no contact with the metal ground.

[0009] Compared with the background technology, the present invention has the following advantages: The present invention designs a 1-bit (180°) radiating element based on a double-chip microstrip patch. The two rectangular patches of the main body are bilaterally symmetrical, and each rectangular patch is equipped with rectangular branches at the outer corners to achieve a wider range of phase control. To address the high loss problem of terahertz metasurface antennas, the present invention designs a MEMS control switch between the two rectangular patches. Its metal electrode is connected to the bias circuit through a TGV through-hole to control the MEMS switch to different operating states. Compared with traditional control devices such as phase change materials, varactor diodes, and PIN switches, the MEMS switch has lower insertion loss and higher integration. The metasurface antenna unit utilizes the different operating states of the MEMS switch to change the surface current pattern of the double-chip microstrip patch, thereby achieving a 180° (1-bit) reflection phase difference of the radiating element. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the technical solution of the present invention, the following briefly describes the drawings required for use in the embodiments.

[0011] Figure 1 It is an exploded view of the overall structure of the present invention; Figure 2 1-Bit radiation unit in the present invention; Figure 3 A top view of the double-piece microstrip patch of the present invention; Figure 4 is a top view of the metal clamped beam of the present invention; Figure 5 is a schematic diagram of a MEMS control switch in the present invention; Figure 6 This is a diagram showing the relative positions of the double-chip microstrip patch, the MEMS switch anchor region, and the metal drive electrode in the present invention; Figure 7 is a cross-sectional view of the terahertz metasurface unit of the present invention; Figure 8 A top view of the metal ground in the present invention; Figure 9 is a schematic diagram of a bias circuit in the present invention; Figure 10 is the reflection phase diagram of the metasurface unit in the open / closed state of the MEMS switch; Figure 11 This is the reflection amplitude diagram of the metasurface unit when the MEMS switch is open / closed. DETAILED DESCRIPTION

[0012] To facilitate those skilled in the art to understand the technical content of the present invention, the present invention is further described below with reference to the accompanying drawings.

[0013] The terahertz metasurface antenna unit comprises two quartz glass dielectric substrates 1: an upper quartz glass dielectric substrate and a lower quartz glass dielectric substrate. A bias circuit 8 is provided on the lower surface of the lower quartz glass dielectric substrate, while a metal ground 3 is provided on the lower surface of the upper quartz glass dielectric substrate and a 1-bit radiating element is provided on the upper surface.

[0014] Among them, the 1-Bit radiation unit consists of a double-chip microstrip patch and a MEMS switch 5 located in the middle of the double-chip microstrip patch; the double-chip microstrip patch is symmetrical on the left and right, and the metal connecting line 10 in the middle is provided with an opening structure. The two rectangular patches 4 of the double-chip microstrip patch are symmetrical on the left and right, and each rectangular patch 4 has a rectangular defect at the outer end corner; 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, which is composed of a metal fixed support beam 11, a silicon nitride dielectric layer 6, and a metal drive electrode 7 from top to bottom.

[0015] The bottom of the metal drive electrode 7 is connected to the bias circuit 8 through the TGV via 2, which is used to control the different operating states of the MEMS switch 5. The different operating states of the MEMS switch 5 change the surface current pattern of the two-piece microstrip patch, thereby achieving a 180° (1-bit) reflection phase difference of the radiating element.

[0016] The terahertz dual-chip metasurface antenna unit controlled by the MEMS switch 5 is realized through micro-nano metal surface processing technology. The specific processing steps are as follows: Step 1: 400 μm thick quartz substrate, surface cleaning; Step 2: Sputtering the seed layer of the double-chip microstrip patch and the metal drive electrode 7, followed by electroplating thickening to a thickness of 1μm; Step 3: Grow a SiN dielectric layer at the capacitor location using a PECVD system with a thickness of 0.1 μm; Step 4: Spin-coat a polyimide sacrificial layer with a thickness of 2 μm; Step 5: Etch the anchor area structure on the sacrificial layer, then sputter the seed layer and thicken it by electroplating. The anchor area height is 2μm. Step 6: Prepare a metal clamping beam 5 by sputtering a seed layer and then thickening it with electroplating, with a thickness of 1 μm; Step 7: Release the sacrificial layer to obtain a suspended MEMS clamped beam.

[0017] The following is a more specific embodiment: like Figure 1Figure 1 shows an exploded view of a terahertz dual-chip metasurface unit controlled by a MEMS switch. The unit comprises upper and lower quartz glass dielectric substrates 1, a TGV through-hole 2 extending through the two substrates, a metal ground plane 3 located between the two quartz glass dielectric substrates 1, a dual-chip microstrip patch located on the upper surface of the upper quartz glass dielectric substrate, a MEMS switch 5, a silicon nitride dielectric layer 6 of the MEMS switch 5, a metal drive electrode 7 of the MEMS switch 5, and a bias circuit 8 located on the lower surface of the lower quartz glass dielectric substrate.

[0018] The dielectric constant of the quartz glass dielectric substrate 1 is 3.78, and the thickness of the substrate is 400 μm.

[0019] Figure 2 The figure shows a top view of a 1-bit radiation unit, which includes a double-chip microstrip patch and a MEMS switch 5 . The MEMS switch 5 is arranged in the middle of two rectangular patches 4 .

[0020] Figure 3 The figure shows a top view of the double-piece microstrip patch. The center frequency of the metasurface unit in this example is 300GHz. According to the operating frequency, the size of each rectangular patch 4 of the double-piece 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 metal connecting wires 10. The size of the metal connecting wires 10 is L 3=0.04mm, W 3 = 0.06 mm. In the operating state, when a surface current flows from one patch to the other, the metal connecting wire 10 is disconnected in the middle. The metal clamping beam 11 of the MEMS switch 5 is then used to control its on / off state, thereby changing the direction of the surface current and achieving a 180° phase difference in the reflected electromagnetic wave.

[0021] MEMS switch structure reference Figure 4 and Figure 5 It includes a metal fixing beam 11, a metal anchor point 12, a metal driving electrode 7, and a silicon nitride dielectric layer 6. The metal fixing beam 11, the metal contact 13, the metal anchor point 12, and the metal driving electrode 6 are all made of gold. The metal fixing beam 11 is designed as a crane leg structure. Figure 4 The main body is rectangular, with rectangular hollows and circular through holes on the pull-down parts on both sides. 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 thus reduce the driving voltage value; its purpose is to facilitate the release of the sacrificial layer during processing, and at the same time further reduce the driving voltage value.

[0022] The dimensions of the metal clamped beam 11 are: 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.

[0023] Figure 6 The figure shows the relative positions of the double-chip microstrip patch, the MEMS switch anchor area, and the metal drive electrode. The size of the metal drive 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.

[0024] The metal drive electrode 7 of the MEMS switch 5 is connected to the bias circuit 8 on the lower surface through the TGV through-hole 2. Using electrostatic force, the metal clamping beam 11 of the MEMS switch 5 is located at different heights, thereby changing the surface current distribution between the two-piece microstrip patch and achieving a 180° (1-bit) reflection phase difference of the radiating element. Figure 7 The figure shows a cross-sectional view of a terahertz metasurface unit, where the TGV through-hole 2 penetrates two layers of quartz glass substrates and the metal ground 3, and is connected to a metal driving electrode 7 and a bias circuit 8, respectively.

[0025] A circular groove is opened on the metal ground 3 for passing the TGV through hole 2, such as Figure 8 shown.

[0026] The bias circuit 8 is located on the lower surface of the bottom quartz glass substrate and is used to provide a DC driving voltage to the MEMS switch 5. Figure 9 As shown, the through hole at the end of the bias circuit 8 is connected to the TGV through hole 2, and the other end can be connected to the control circuit board through a flat cable.

[0027] The transmission characteristic curve of the metasurface unit is obtained using 3D simulation software: 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°.

[0028] 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.

[0029] 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.

2. The terahertz dual-chip metasurface antenna unit controlled by a MEMS switch according to claim 1, characterized in that: 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.

3. The MEMS switch-controlled terahertz dual-chip metasurface antenna unit according to claim 2, 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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