A terahertz programmable metasurface unit of an RF MEMS switch

Abstract

The application discloses a terahertz programmable metasurface unit of an RF MEMS switch and belongs to the technical field of communication, comprising: a second substrate, a positive control line, a back cover ground, a first substrate, a direct current grounding column, an upper patch, a signal line, an RF MEMS switch and a direct current bias line structure. The switch is controlled to be turned off and turned on through direct current voltage change, and a metasurface unit 180° reflection phase difference is realized. The application achieves the following technical effects: (1) the 180° reflection phase difference working bandwidth is large, the reflection phase difference range is 172° to 193° at 285GHz to 320GHz; (2) the reflection phase is high in linearity, the reflection phase range of the switch down state is 117° to 52° at 285GHz to 320GHz, and the reflection phase range of the switch up state is -53° to -129°; (3) the processing technology requirement is low, the second layer anchor point and the lower electrode of the switch are connected through the bias line respectively, and the number of electrode punching is reduced; and (4) the bias line part uses metal, the bias line voltage division is reduced, and the driving voltage is reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of communication, and particularly relates to a terahertz programmable metasurface unit of an RF MEMS switch. BACKGROUND

[0002] The frequency band range of terahertz waves is 0.1 THz-10 THz, and the terahertz waves have the characteristics of high frequency, wide bandwidth, strong transmission capacity and rich information carrying, and have wide application prospects in the fields of wideband communication, radar detection and imaging. However, the terahertz waves have the disadvantage of large spatial path loss. In order to solve the problem, the phased array technology can be used to improve the antenna gain and the beam scanning method. Compared with the T / R component, the metasurface has advantages in cost, power consumption and weight in regulating and controlling the electromagnetic wave phase.

[0003] The metasurface refers to an artificial structure that realizes flexible regulation and control of electromagnetic waves by periodically or non-periodically arranging sub-wavelength structure units. The metasurface unit can be independently designed to realize independent regulation and control of the amplitude and phase of electromagnetic waves, so that more complex field distribution results can be obtained. Based on the discontinuity of the phase or amplitude, the programmable metasurface can discretize the units into a limited type and describe them with digital codes. For example, if the reflection phases of two units differ by 180° and the amplitudes are similar, then the two codes of "0" and "1" can be obtained. The metasurface array mainly faces the 5G and 6G wireless communication fields, and can be spliced, installed and deployed in hot traffic areas such as stadiums and shopping malls to cooperatively cover the blind spots with existing base stations. For the programmable metasurface, the pin diode phase modulation has the advantages of convenient control and easy integration, but has the disadvantages of high insertion loss, low isolation, low linearity, small 180° phase difference bandwidth and difficulty in independent control of a single unit.

[0004] The electrostatically driven RF-MEMS switch realizes the opening and closing function by using the electrostatic force attraction of the upper and lower plates. Compared with other solid-state devices (pin diode, MOSFET switch and HEMT switch), the RF-MEMS switch has the advantages of low insertion loss, high isolation, low power consumption, high linearity and high integration, but has the problem of reliability. For the electrostatically driven switch, adhesion, wear, dielectric damage, fatigue damage and warping deformation problems may occur due to temperature, load, vibration and charging. SUMMARY

[0005] In view of the above problems, the application discloses a terahertz programmable metasurface unit of an RF MEMS switch,

[0006] The application comprises:

[0007] The second substrate 16 has a square cross section and a sub-wavelength scale side length.

[0008] Positive electrode control line 18, formed on the lower surface of the second substrate 16, for RF MEMS switch power supply;

[0009] Back ground 15, formed on the upper surface of the second substrate 16, as a ground electrode and reflect electromagnetic wave;

[0010] First substrate 14, formed on the upper surface of the back ground 15;

[0011] DC ground column 12, through the first substrate 14, the length and the thickness of the first substrate 14 is the same, its axis is located on the symmetry axis of the first substrate, for connecting the RF MEMS switch lower electrode 6 and the back ground 15;

[0012] DC positive column 13, the length of the first substrate 14, the back ground 15, the second substrate 16 thickness is the sum of the three, and through the three, its axis is located on the symmetry axis of the first substrate, for connecting the RF MEMS switch second layer anchor point 5 and the positive electrode control line 18;

[0013] The upper patch 7, formed on the upper surface of the first substrate 14, symmetrically distributed on both sides of the DC positive column 13, for scattering terahertz wave;

[0014] Signal line 8, formed on the upper surface of the first substrate 14, symmetrically distributed on both sides of the DC positive column 13, and connected with the upper patch 7, for connecting the upper patch 7;

[0015] RF MEMS switch 6, 5, 4, 3, 2, 17, 1, formed on the first substrate 14, located in the upper patch 7, across the signal line 8, for connecting or disconnecting the signal line 8 to realize the scattering electromagnetic wave 180° reflection phase difference;

[0016] DC bias line structure 11, 10, 9, formed on the upper surface of the first substrate 14, for providing DC voltage to the RF MEMS switch.

[0017] In some embodiments of the present application, the back ground 15 has a circular hole to prevent short circuit with the DC positive column 13.

[0018] In some embodiments of the present application, the RF MEMS switch includes the lower electrode 6, the second layer anchor point 5, the electrode dielectric layer 4, the first layer anchor point 3, the upper metal electrode 2, the signal bridge 17, and the skirt beam 1.

[0019] The lower electrode 6, formed on the first substrate 14, and located on both sides of the signal line 8, its side length is greater than the diameter of the DC ground column 12, as the negative electrode of the switch;

[0020] The second layer anchor point 5 is formed on the first substrate 14 and located on both sides of the signal line 8, with an edge length equal to the diameter of the direct current positive column 13, a thickness same as the lower electrode 6, the upper patch 7 and the signal line 8, and a length greater than the first layer anchor point 3, serving as the negative electrode of the switch;

[0021] The electrode dielectric layer 4 is formed on the lower electrode 6, distributed on both sides of the signal line 8, and has an area greater than the lower electrode 6, for isolating the lower electrode 6 and the upper metal electrode 2;

[0022] The first layer anchor point 3 is formed on the second layer anchor point 5, distributed on both sides of the signal line 8, and adopts a round corner transition on one side close to the signal line 8, for fixing the upper metal electrode and forming a switch gap;

[0023] The upper metal electrode 2 is located above the electrode dielectric layer 4, distributed on both sides of the signal line 8, and fixed on the first layer anchor point 3 at both ends, serving as the upper electrode of the switch, driving the signal bridge 17 to press down after applying a driving voltage, with a beam structure of a quadratic curve and a circular arc transition at the beam joint, a width less than the upper patch middle gap, and a release hole on the upper metal electrode 2, for releasing the sacrificial layer and reducing the pressing down damping;

[0024] The signal bridge 17 is located directly above the signal line 8 and at the same level as the upper metal electrode 2, for connecting or disconnecting the signal line 8, and has two circular contacts below, for increasing the pressing force of the switch;

[0025] The skirt beam 1 is formed on the upper metal electrode 2 and covers the upper metal electrode 2 and the signal bridge 17, for providing a switch restoring force, avoiding the switch warping deformation caused by uneven stress distribution, improving the switch fatigue life, separating the upper metal electrode 2 and the signal bridge 17, and isolating the influence of direct current on radio frequency signals, and has a release hole on the upper metal electrode 2, for releasing the sacrificial layer and reducing the pressing down damping.

[0026] In some embodiments of the present application, the direct current bias line structure includes a non-metal bias line 11, an upper electrode metal bias line 10 and a lower electrode metal bias line 9;

[0027] The non-metal bias line 11 is formed on the first substrate 14, symmetrically distributed on both sides of the direct current ground column 12, for connecting the second layer anchor point 5 and the lower electrode 6;

[0028] The upper electrode metal bias line 10 is symmetrically distributed on both sides of the signal line 8, connected with the non-metal bias line 11 and the second layer anchor point 5, and should be deviated from the upper patch 7 as much as possible to reduce the influence on the displacement current, for connecting the second layer anchor point 5 and reducing the voltage division caused by the resistance of the direct current bias line;

[0029] The lower electrode metal bias line 9 is symmetrically distributed on both sides of the signal line 8, connected with the non-metal bias line 11 and the lower electrode 6, and should be as far away from the upper patch 7 as possible to reduce the influence on the displacement current, and acts as a connection between the lower electrode 6 and reduces the voltage division caused by the resistance of the DC bias line.

[0030] The technical effects achieved by the present application are as follows:

[0031] 1. The operating bandwidth of the 180° reflection phase difference is large, ranging from 285 GHz to 320 GHz, and the reflection phase difference ranges from 172° to 193°;

[0032] 2. The reflection phase has high linearity, ranging from 117° to 52° in the switch down state and from -53° to -129° in the switch up state at 285 GHz to 320 GHz;

[0033] 3. The RF MEMS switch has high mechanical reliability, uses a skirt beam structure, and the stress distribution is uniform after the switch is deformed, reducing the warping deformation of the switch; the beams are connected by circular arcs, without stress concentration; the circular arc connection increases the length of the connection, reduces the risk of fracture caused by switch cycling, and improves the fatigue life of the switch;

[0034] 4. The processing technology requirement is low, the second layer anchor point and the lower electrode of the switch are connected by bias lines, reducing the number of electrode holes, reducing manufacturing costs, and improving manufacturing efficiency;

[0035] 5. The bias line part uses metal, reducing the voltage division of the bias line and reducing the driving voltage.

[0036] The additional advantages, objects, and features of the present application will be in part apparent and in part pointed out in the description below, and will be learned from a reading of the following specification and by practicing the present application according to the principles described below. The objects and other advantages of the present application will be realized and attained by the structure particularly pointed out in the specification and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 It is a sequence number and size diagram of a terahertz programmable metasurface unit section of an RF MEMS switch;

[0038] Figure 2 It is a sequence number explosion diagram of a terahertz programmable metasurface unit of an RF MEMS switch;

[0039] Figure 3 It is a three-dimensional model diagram of a terahertz programmable metasurface unit of an RF MEMS switch;

[0040] Figure 4A key dimension and top view of a terahertz programmable metasurface unit of an RF MEMS switch;

[0041] Figure 5 A schematic diagram of a strain simulation of an RF MEMS switch;

[0042] Figure 6 A simulation diagram of a driving voltage and unstable position of an RF MEMS switch;

[0043] Figure 7 A simulation diagram of a stress fatigue life of an RF MEMS switch with a skirt structure;

[0044] Figure 8 A simulation diagram of a stress fatigue life of an RF MEMS switch without a skirt structure;

[0045] Figure 9 A simulation diagram of a reflection phase difference of a terahertz programmable metasurface unit of an RF MEMS switch;

[0046] Figure 10 A simulation diagram of S11 of a terahertz programmable metasurface unit of an RF MEMS switch;

[0047] Figure 11 A 1x16 linear array 3D directional diagram of a terahertz programmable metasurface unit of an RF MEMS switch with "0011" coding;

[0048] Figure 12 A 1x16 linear array 2D directional diagram of a terahertz programmable metasurface unit of an RF MEMS switch with "0011" coding.

[0049] In the figure, 1 is a skirt beam, 2 is an upper metal electrode, 3 is a first layer of anchor points, 4 is an electrode dielectric layer, 5 is a second layer of anchor points, 6 is a lower electrode, 7 is an upper patch, 8 is a signal line, 9 is a lower electrode metal bias line, 10 is an upper electrode metal bias line, 11 is a non-metal bias line, 12 is a DC ground column, 13 is a DC positive column, 14 is a first substrate, 15 is a back ground, 16 is a second substrate, 17 is a signal bridge, and 18 is a positive control line. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is further described in detail below in combination with embodiments and drawings. Herein, the illustrative embodiments of the present application and their descriptions are used to explain the present application, but not as a limitation of the present application.

[0051] In view of the problems of high insertion loss, low isolation, low linearity, small 180-degree phase difference bandwidth and difficulty in independent control of a single unit of the pin diode of the programmable metasurface unit in the prior art and the problems of stress concentration, fatigue damage and warping deformation of the RF MEMS switch, the application provides a terahertz programmable metasurface unit of an RF MEMS switch, and the principle is that when no direct current voltage is applied to the back ground 15 and the positive control line 18, the switch is in an up state; when the direct current voltage is applied, the upper metal electrode 2 is driven to press down the signal bridge 17 due to the action of the electrostatic force between the upper metal electrode 2 and the lower electrode 6; when the voltage of the RF MEMS switch reaches the driving voltage, the signal bridge 17 and the signal line 8 are in contact and conductive, at this time, the switch is in a down state, the electromagnetic wave reflection phase difference of the up state and the down state is 180 degrees, and the “1bit” programmable function of the metasurface unit is realized; a unit upper patch, signal line and signal bridge structure is designed, so that the metasurface unit has a large working bandwidth and high linearity of the reflection phase in the 180-degree reflection phase difference; a RF MEMS switch skirt beam structure is designed, so that the stress distribution is uniform after the switch is pulled down and deformed, the warping deformation of the switch is reduced, and the fatigue life is improved; a RF MEMS switch composite beam structure is designed, so that the electrode and the signal bridge are separated, and the interference of the direct current on the radio frequency signal is reduced; a unit bias line structure is designed, so that the number of electrode perforations can be reduced, and each switch can be controlled independently; a unit metal and non-metal combined bias line is designed, so that the bias line voltage division can be reduced.

[0052] The isolation degree is defined as the ratio of the power of the radio frequency signal leaked to other ports to the input power, and the unit can be decibel (dB); the isolation degree is an index for measuring the quality of the switch, when the switch is qualified, the isolation between the ports is good, and the signal leakage is minimum.

[0053] The insertion loss is the loss of load power caused by inserting components or devices in the transmission system, and is represented by the ratio of the input power to the power transmitted to the load, and the unit can be decibel (dB).

[0054] The reflection phase refers to the phase of the reflected electromagnetic wave of the unit at a distance of 1 micrometer from the surface of the unit.

[0055] The reflection phase difference refers to the reflection phase of the unit in the up state of the RF MEMS switch minus the reflection phase of the unit in the down state of the RF MEMS switch.

[0056] Terahertz refers to electromagnetic waves with a frequency in the range of 0.1-10 THz.

[0057] The stress refers to the internal force between parts on a unit area of an object when the object is deformed due to external factors such as force and temperature.

[0058] Stress concentration is the phenomenon of local increase of stress in an object, which generally occurs in the place where the shape of the object changes sharply.

[0059] Fatigue life is the number of stress cycles experienced by a material before it fails.

[0060] Drive voltage is the minimum operating voltage of a switch from up state to down state, and the switch generally has an unstable state at one-third of the pull-down gap, at which the pull-down voltage is the drive voltage.

[0061] Basquin's law is generally expressed as σa = σ'(2N) b , which can be used to describe high-cycle fatigue, where σa represents fatigue strength, σ' represents fatigue strength coefficient, N represents fatigue life (cycle number), and b represents fatigue strength index.

[0062] Figure 1 It is a sequence number and size schematic diagram of a THz programmable metasurface unit profile of an RF MEMS switch, Figure 2 It is a sequence number explosion diagram of a THz programmable metasurface unit of an RF MEMS switch, Figure 3 It is a three-dimensional model diagram of a THz programmable metasurface unit of an RF MEMS switch, Figure 4 It is a key size and top view of a THz programmable metasurface unit of an RF MEMS switch, Figure 5 It is a strain simulation schematic diagram of an RF MEMS switch. Figure 1 And Figure 4 The structure key size in table 1.

[0063] As shown in Figure 1 , Figure 2 , Figure 3 , Figure 4 And Figure 5 The present application provides a THz programmable metasurface unit of an RF MEMS switch, which comprises:

[0064] The second substrate 16 has a square cross section, a subwavelength size, and a quartz glass material, and has a relative dielectric constant of 3.78 and a dielectric loss tangent of 0.0008, which has the advantages of low cost and mature process;

[0065] The positive control line 18 is formed under the second substrate 16 and is used for power supply of the RF MEMS switch, and is made of Au with a thickness of 0.5 um;

[0066] Back ground 15, formed on the second substrate 16, as a ground electrode and reflect electromagnetic wave, material is Au, thickness is 1um, formed by two layers of 0.5um Au-Au bonding, with a circular hole diameter of 80um, so that the DC positive column 13 passes through, preventing short circuit;

[0067] The first substrate 14 is combined with the second substrate by the 0.5um back ground 15 below, using Au-Au bonding, the material is quartz glass, the relative dielectric constant is 3.78, and the dielectric loss tangent is 0.0008;

[0068] DC ground column 12, passing through the first substrate 14, the cylindrical axis is located on the symmetry axis of the first substrate 14, connecting the RF MEMS switch lower electrode 6 and the back ground 15, the material is Au, the diameter is 50um, because there is a 5um error in the hole diameter, so the DC ground column 12 should be as far away from the signal line 8 as possible to prevent its influence on the radio frequency signal;

[0069] DC positive column 13, the cylindrical axis is located at the center of the second layer anchor point, the material is Au, the diameter is 50um, connecting the RF MEMS switch second layer anchor point 5 and the positive control line 18, because the nearest distance between the centers of adjacent holes is 120±10um, so the DC positive column 13 and the DC ground column 12 can only be designed on both sides of the signal line 8;

[0070] The upper patch 7 is formed on the first substrate 14, symmetrically distributed on both sides of the DC positive column 13, used for scattering terahertz waves, and the signal line 8, the lower electrode 6, the second layer anchor point 5, the lower electrode metal bias line 9, and the upper electrode metal bias line 10 are located on the same layer, and the materials are all Au, with a thickness of 0.5um;

[0071] The signal line 8 is formed on the first substrate 14, symmetrically distributed on both sides of the DC positive column 13, and connected with the upper patch 7, used for connecting the upper patch 7, the signal line 8 is 15um wide, larger than the signal bridge width, preventing processing errors from causing poor contact, with a spacing of 30um;

[0072] The RF MEMS switch is formed on the first substrate 14, located in the middle of the upper patch 7, crossing the signal line 8, used for connecting or disconnecting the signal line 8 to realize a 180° reflection phase difference of scattered electromagnetic waves, the switch in detail includes the lower electrode 6, the second layer anchor point 5, the electrode dielectric layer 4, the first layer anchor point 3, the upper metal electrode 2, the signal bridge 17, and the skirt beam 1;

[0073] The second layer anchor point 5 is formed on the first substrate 14 and located on both sides of the signal line 8, tangent to the boundary and the DC positive pole 13, as the negative pole of the switch, made of Au, with a thickness of 0.5 um. Since the MEMS processing process is to first make a 1 um first layer anchor point 3 and then make a second layer anchor point 5, the length a10 of the second layer anchor point 5 is 50 um, which is greater than the length a11 of the first layer anchor point 3, i.e. 40 um, and covers the first layer anchor point 3, so that the contact is good;

[0074] The electrode dielectric layer 4 is formed on the lower electrode 6 and distributed on both sides of the signal line 8, made of Si3N4, with a relative dielectric constant of 7.6, and serves to form a capacitor structure with the lower electrode and the upper metal electrode, isolate the DC short circuit, and has a rectangular shape with a size greater than the lower electrode to avoid short circuit caused by direct contact between the lower click and the upper metal electrode;

[0075] The first layer anchor point 3 is formed on the second layer anchor point 5 and distributed on both sides of the signal line 8, with a round corner transition on one side close to the signal line 8, for fixing the upper metal electrode and forming a switch gap, made of Au, with a thickness of 1 um. The upper metal electrode 2 is located above the electrode dielectric layer 4 and distributed on both sides of the signal line 8, with both ends fixed on the first layer anchor point 3, as the upper electrode of the switch, which drives the signal bridge 17 to press down after applying a driving voltage. The beam structure of the signal bridge 17 is a quadratic curve, and the beam joint is a circular arc transition. The width of the signal bridge 17 is smaller than the middle gap of the upper patch. The signal bridge 17 has a release hole for releasing the sacrificial layer and reducing the pressing damping. The signal bridge 17 is made of Au, with a thickness of 0.5 um;

[0076] The signal bridge 17 is located directly above the signal line 8 and at the same level as the upper metal electrode 2, for connecting or disconnecting the signal line 8. The signal bridge 17 is made of Au, with a thickness of 0.5 um and a width of 10 um. The signal bridge 17 has two circular contacts below to increase the pressing force of the switch. The contact area between the signal bridge 17 and the signal line 8 is 10 umx10 um. The contact area has a great influence on the radio frequency performance. Simulation shows that the smaller the contact area, the smaller the insertion loss of high-frequency electromagnetic waves, and the higher the isolation degree.

[0077] The skirt beam 1 is formed on the upper metal electrode 2 and covers the upper metal electrode 2 and the signal bridge 17. The skirt beam 1 serves to provide a switch restoring force, avoid switch warping deformation caused by uneven stress distribution, improve switch fatigue life, and separate the upper metal electrode 2 and the signal bridge 17 to isolate the influence of DC on radio frequency signals. The skirt beam 1 has a release hole for releasing the sacrificial layer and reducing the pressing damping. The skirt beam 1 is made of SiO2, with a thickness of 1 um.

[0078] Direct current bias lines formed on the first substrate 14 for providing direct current voltage to the RF MEMS switch, including a non-metal bias line 11, an upper electrode metal bias line 10, and a lower electrode metal bias line 9; the non-metal bias line 11 is formed on the first substrate 14 and symmetrically distributed on both sides of the direct current grounding column 12, for connecting the second layer anchor point 5 and the lower electrode 6; the upper electrode metal bias line 10 is symmetrically distributed on both sides of the signal line 8, connected with the non-metal bias line 11 and the second layer anchor point 5, and should be as far away from the upper patch 7 as possible to reduce the influence on the displacement current, and functions as connecting the second layer anchor point 5 and reducing the voltage division caused by the resistance of the direct current bias line; the lower electrode metal bias line 9 is symmetrically distributed on both sides of the signal line 8, connected with the non-metal bias line 11 and the lower electrode 6, and should be as far away from the upper patch 7 as possible to reduce the influence on the displacement current, and functions as connecting the lower electrode 6 and reducing the voltage division caused by the resistance of the direct current bias line.

[0079] Figure 6 It is a simulation diagram of the driving voltage and unstable position of an RF MEMS switch, in which the horizontal coordinate represents the displacement of the center point of the signal bridge, and the vertical coordinate represents the driving voltage required for the center point of the signal bridge to reach the required position; when the center point of the signal bridge is lowered by 0.4 um, the required driving voltage is 8.8 V, at which the electrostatic force and the restoring force of the switch reach equilibrium, the switch is in an unstable state, and finally closes. When the distance of the center point of the signal bridge is lowered by more than 0.4 um, Figure 6 In the simulation diagram, the driving voltage decreases because the distance between the electrodes becomes smaller, the plate capacitance becomes larger, and the driving voltage required for the switch to reach equilibrium decreases.

[0080] Figure 7 It is a stress fatigue life simulation diagram of an RF MEMS switch with a skirt structure; Figure 8 It is a stress fatigue life simulation diagram of an RF MEMS switch without a skirt structure. When the switch is pressed from the initial state to 0.8 um and is cycled 1E10 times, the fatigue strength coefficient σ'

[0081] According to the literature, the fatigue strength coefficient σ' is set to 68 MPa, and the fatigue strength index b is set to 0.9, Figure 7 The simulation result shows that the RF MEMS switch with a skirt structure fails due to fatigue after being cycled 1.32E8 times, Figure 8 The simulation result shows that the RF MEMS switch without a skirt structure fails due to fatigue after being cycled 1.56E6 times, and the stress fatigue life of the switch with a skirt structure is improved by 100 times compared with the switch without a skirt structure.

[0082] Figure 9is a simulation diagram of the reflection phase difference of a terahertz programmable metasurface unit of an RF MEMS switch, and it can be seen that the reflection phase difference ranges from 172° to 193° when the metasurface unit is in the “0” and “1” states, and the working frequency ranges from 285 GHz to 320 GHz, so the reflection phase difference is greater than 180°

[0083] The reflection phase difference has a wide working bandwidth, and the reflection phase of the metasurface unit has high linearity, and the reflection phase ranges from 117° to 52° when the switch is in the down state, and the reflection phase ranges from -53° to -129° when the switch is in the up state, within the frequency range of 285 GHz to 320 GHz.

[0084] Figure 10 is a simulation diagram of the S11 of a terahertz programmable metasurface unit of an RF MEMS switch, and it can be seen that the unit reflection amplitude is less than 2 db when the switch is in the up state and the down state within the frequency range of 280 GHz to 300 GHz, the unit reflection amplitude is less than 3 db when the switch is in the up state and the down state within the frequency range of 280 GHz to 315 GHz, and the unit reflection amplitude is less than 1 db when the switch is in the up state and the down state within the frequency range of 280 GHz to 320 GHz if the lower electrode metal bias line (9) and the upper electrode metal bias line (10) are replaced by TaN material non-metal bias lines.

[0085] Figure 11 is a 1x16 linear array 3D directional diagram of a terahertz programmable metasurface unit of an RF MEMS switch with “0011” coding, Figure 12 is a 1x16 linear array two-dimensional directional diagram of a terahertz programmable metasurface unit of an RF MEMS switch with “0011” coding. Combined with Figure 11 and Figure 12 When using “0011” coding as a subarray, a 1x16 linear array is simulated in HFSS, and ±30° dual-beam is obtained.

[0086] Table 1 Size of unit

[0087]

[0088]

[0089] The above parameters are only examples, and the application is not limited thereto, and reasonable adjustments can also be made based on specific application scenarios.

Claims

1. A terahertz programmable metasurface unit for an RF MEMS switch, characterized in that, include: The second substrate (16) has a square cross-section and a side length on a subwavelength scale; The positive control line (18) is located on the lower surface of the second substrate (16) and is connected to the DC positive terminal (13); Backing (15) is located on the upper surface of the second substrate (16); The first substrate (14) is located on the upper surface of the backing ground (15); A DC grounding post (12) passes through the first substrate (14) and has the same length and thickness as the first substrate (14); The DC positive terminal (13) has a length equal to the sum of the thicknesses of the first substrate (14), the back cover (15), and the second substrate (16), and passes through all three; the DC ground terminal (12) and the DC positive terminal (13) are parallel to each other and are both located on the line of symmetry of the first substrate (14); The upper patch (7) is provided in two sets, both located on the upper surface of the first substrate (14), and the two sets of upper patches (7) are symmetrically distributed on both sides of the DC positive terminal (13); The signal line (8) is located on the upper surface of the first substrate (14), between the two sets of upper patches (7), and connected to the two sets of upper patches (7); An RF MEMS switch is located above the signal line (8); The RF MEMS switch includes a lower electrode (6), a second anchor point (5), an electrode dielectric layer (4), a first anchor point (3), an upper metal electrode (2), a signal bridge (17), and a skirt beam (1). Two lower electrodes (6) are provided, both formed on the first substrate (14) and located at both ends of the signal line (8). The side length of each lower electrode is greater than the diameter of the DC grounding post (12). The second layer anchor point (5) has two, both formed on the first substrate (14), and located on the outside of the two lower electrodes (6), and the side length of the two second layer anchor points (5) is equal to the diameter of the DC positive electrode column (13); The first layer of anchor points (3) has two points, which are located at the top of the corresponding second layer anchor points (5); The upper metal electrode (2) is provided in two parts, which are respectively installed on the top of the corresponding first layer anchor point (3). The two upper metal electrodes (2) extend towards each other and there is a gap between them. The signal bridge (17) is located between two upper metal electrodes (2) and is supported by a skirt beam (1); The skirt beam (1) is formed on two upper metal electrodes (2) and covers the upper metal electrodes (2) and the signal bridge (17), and separates the upper metal electrodes (2) and the signal bridge (17). It has a release hole for sacrificial layer release and reducing down-pressure damping. The signal bridge (17) is located directly above the signal line (8) and on the same level as the upper metal electrode (2). It is used to connect or disconnect the signal line (8) and has two circular contacts below it. The RF MEMS switch also includes a DC bias line structure, which includes a non-metallic bias line (11), an upper electrode metal bias line (10), and a lower electrode metal bias line (9). Two non-metallic bias lines are provided, corresponding to the upper electrode and the lower electrode respectively; One of the lower electrodes is connected to the DC grounding post (12), and the two lower electrodes are connected in sequence through the lower electrode metal bias line a, the non-metal bias line a and the lower electrode metal bias line b. One of the second-layer anchor points (5) is connected to the DC positive terminal; the two second-layer anchor points (5) are connected through the upper electrode metal bias line a, the non-metal bias line b and the upper electrode metal bias line b.

2. The terahertz programmable metasurface unit for an RF MEMS switch according to claim 1, characterized in that, The back cover (15) is provided with a circular hole through which the DC positive terminal (13) passes.

3. The terahertz programmable metasurface unit for an RF MEMS switch according to claim 1, characterized in that, Two non-metallic bias lines (11) are formed on the first substrate (14) and are symmetrically distributed on both sides of the DC grounding post (12).

4. The terahertz programmable metasurface unit for an RF MEMS switch according to claim 1, characterized in that, The upper electrode metal bias line (10) is symmetrically distributed on both sides of the signal line (8), and is connected to the non-metallic bias line b and the second layer anchor point (5), and is offset from the upper patch (7).

5. The terahertz programmable metasurface unit for an RF MEMS switch according to claim 1, characterized in that, The lower electrode metal bias line (9) is symmetrically distributed on both sides of the signal line (8), and is connected to the non-metallic bias line a and the lower electrode (6), and is offset from the upper patch (7).

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