Terahertz wave band composite beam RF MEMS switch with low driving voltage

Abstract

The invention discloses a terahertz wave band composite beam RF MEMS switch with low driving voltage, and belongs to the field of radio frequency front-end devices. The device is composed of a direct current port metal block, a direct current bias line, a microstrip line matching structure, a composite beam MEMS switch, a composite beam middle conduction structure, a metal electrode of a composite beam, a silicon nitride insulating layer, a quartz glass substrate, a coplanar waveguide metal ground and a metal ground. The composite beam MEMS switch is formed by combining a silicon dioxide material clamped beam and a metal beam adsorbed below the silicon dioxide material clamped beam, a direct current port is connected to the anchor point position of the metal beam and a metal electrode through a direct current bias line, and different direct current voltages can be input through the direct current port to control the lifting state of the composite beam and the pull-down state of the composite beam adsorbed to the electrode. The two switches respectively correspond to an off state and an on state of the switch. The composite beam MEMS switch works below 140GHz, so that low driving voltage, low insertion loss and high isolation are realized. The reaction time of microsecond magnitude is achieved, destructive deformation is not prone to occurring, the structure is simple, and manufacturing is easy.

Description

Technical Field

[0001] The present invention relates to the design of a terahertz band composite beam RF MEMS switch with low driving voltage, which is mainly used in satellite communication systems in the terahertz frequency band and belongs to the field of radio frequency front-end devices. Background Art

[0002] RF MEMS switches are essentially miniature RF devices with three-dimensional structures that are manufactured using micromachining technology to control the on and off states of RF circuits at high speed and accuracy. Compared with PIN diode switches and field effect transistor switches, MEMS switches have many advantages such as lower insertion loss, higher isolation and lighter weight, and are widely used in long-distance communications such as satellite communications, navigation systems and radar systems.

[0003] According to the driving mode of the mechanical structure of MEMS switches, they can be divided into four categories: electrostatic drive, electromagnetic drive, electrothermal drive and piezoelectric drive. Among them, the electrostatic drive technology is relatively mature, the most widely studied, and is currently the most widely used driving mechanism. According to the manufacturing materials of MEMS switches, they can be divided into non-quartz glass switches and quartz glass switches. Quartz glass materials often have high insertion loss due to their high resistance. At present, there are few MEMS switches with high integration, high isolation, low insertion loss and high linearity in the RF field. For example, the MEMS switch working in the terahertz band proposed by Rahul Gogna et al. in 2016 has high integration and can be applied to coplanar waveguides and other transmission line structures. It achieves a return loss of 24-12dB in the frequency range of 180-250GHz, but the insertion loss is relatively high at 1.2-2.7dB.

[0004] In summary, there are currently very few MEMS switches that work in the terahertz band, and most of them do not have good insertion loss characteristics and cannot meet the requirements for communication equipment applications in the terahertz band. Summary of the invention

[0005] In order to solve the problems existing in the background technology, the present invention proposes a terahertz band composite beam RF MEMS switch based on low driving voltage. The composite beam MEMS switch has the characteristics of simple structure, high isolation, low insertion loss, low power consumption, and not easy to produce structural deformation, and can be used in the terahertz band.

[0006] In order to solve the above technical problems, the present invention is achieved through the following technical solutions:

[0007] A low-drive-voltage terahertz-band composite beam RF MEMS switch comprises a quartz glass substrate (16), a coplanar waveguide metal ground (12) and a metal ground (26); the coplanar waveguide metal ground (12) is located on the upper surface of the quartz glass substrate; the metal ground (26) is located on the lower surface of the quartz glass substrate; a DC port metal block, a DC bias line, a microstrip line matching structure (11) and a composite beam MEMS switch are also provided on the upper surface of the quartz glass substrate;

[0008] Wherein, the microstrip line matching structure and the composite beam MEMS switch (15) are both located in an area surrounded by the coplanar waveguide metal ground;

[0009] The DC port metal blocks are provided with two and are respectively located on two sides outside the coplanar waveguide metal ground area; the composite beam MEMS switch (15) is mounted directly above the middle position of the microstrip line matching structure (11); the metal electrodes and bridge piers of the composite beam MEMS switch (15) are connected to the corresponding DC port metal blocks via a DC bias line.

[0010] Furthermore, the composite beam MEMS switch (15) comprises an upper beam (23) and a metal lower beam (24) which are stacked, wherein the metal lower beam is located on the lower surface of the upper beam; the metal lower beam (24) at the middle position of the upper beam (23) is hollowed out, and the middle conductive structure (25) of the metal lower beam is located at the middle position of the upper beam (23), and the middle conductive structure (25) is located directly above the notch of the microstrip line matching structure (11); two metal electrodes are respectively located directly below the left action arm and the right action arm of the lower beam (24); wherein the two metal electrodes are connected to the DC port metal block (1) on the left side through corresponding DC bias lines.

[0011] Furthermore, the material of the upper beam (23) of the composite beam MEMS switch (15) is silicon dioxide.

[0012] Furthermore, the material of the lower beam (24) of the composite beam MEMS switch (15) is gold.

[0013] Furthermore, the middle conducting structure (25) of the composite beam MEMS switch (15) is an H-shaped metal sheet, and four cylindrical contacts are distributed below the H-shaped metal sheet.

[0014] Furthermore, the upper beam (23) of the composite beam MEMS switch (15) is a symmetrical figure with the upper beam H-shaped structure as the middle line, including a left bridge pier, a left connecting arm, a left action arm, a left middle arm, an upper beam H-shaped structure, a right middle arm, a right action arm, a right connecting arm and a right bridge pier connected in sequence from left to right;

[0015] Among them, the bridge piers are connected to the metal lower beams;

[0016] The connecting arm is a folded and curved volute structure, and periodic circular holes are etched on both the left and right action arms.

[0017] Furthermore, the metal lower beam (24) of the composite beam MEMS switch (15) comprises a left arm portion, a left hollow portion, a lower beam H-shaped structure, a right hollow portion and a right arm portion; wherein the left arm portion and the right arm portion are symmetrical to each other; the left arm portion and the right arm portion both comprise a line-connected outer folded and bent ridge structure and an inner action arm; and the inner action arm is etched with periodic circular holes.

[0018] Furthermore, the microstrip line matching structure (11) is composed of input and output trapezoidal gradient microstrip lines for matching, and the middle conduction structure (25) of the composite beam MEMS switch (15) is located directly above the trapezoidal gradient microstrip line structures on both sides, and conduction is achieved when pulled down.

[0019] Furthermore, a silicon nitride insulating layer is provided on the upper surface of the metal electrode of the composite beam MEMS switch (15).

[0020] Compared with the background technology, the present invention has the following advantages:

[0021] a) The switch has a simple structure and is easy to manufacture. It can be applied to radio frequency circuits such as phased array antennas and metasurface reflective array antennas to control their conduction and disconnection.

[0022] b) The switch has high isolation in the off state and low insertion loss in the on state.

[0023] c) The switch adopts a composite beam structure, can work at a low driving voltage, has a short response time, high reliability, and is not prone to breakage during operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a top view of the overall structure of the present invention;

[0025] Figure 2 It is a schematic structural diagram of the upper surface of the quartz glass substrate of the present invention;

[0026] Figure 3 It is a schematic diagram of the structure of the present invention that is not conducting;

[0027] Figure 4 It is a schematic diagram of the conductive structure of the present invention;

[0028] Figure 5 It is a structural schematic diagram of the upper beam of the composite beam MEMS switch in the present invention;

[0029] Figure 6 It is a structural schematic diagram of the lower beam of the composite beam MEMS switch in the present invention;

[0030] Figure 7It is a bottom view of the structure of the composite beam MEMS switch in the present invention with the middle being conductive;

[0031] Figure 8 It is a three-dimensional stereogram of the overall structure of the present invention;

[0032] Fig. 9 is the return loss S of the composite beam MEMS switch in the disconnected state of the present invention 11 , Isolation S 21 curve;

[0033] Fig.10 is the return loss S of the composite beam MEMS switch in the on state of the present invention 11 , Insertion loss S 21 curve. DETAILED DESCRIPTION

[0034] The following is combined with Figure 1-10 The specific implementation modes of the present invention are further described in detail with reference to the accompanying drawings and examples.

[0035] A low-driving-voltage terahertz-band composite beam RF MEMS switch comprises a quartz glass substrate, a metal ground, and a coplanar waveguide metal ground; further comprising a DC port metal block, a DC bias line, a metal electrode, a microstrip line matching structure, and a composite beam MEMS switch; the coplanar waveguide metal ground is located on the upper surface of the quartz glass substrate; the metal ground is located on the lower surface of the quartz glass substrate; the DC port metal block, the metal electrode, and the microstrip line matching structure are all located on the upper surface of the quartz glass substrate;

[0036] There are two DC port metal blocks, divided into two groups; the two groups of DC port metal blocks are located on both sides of the microstrip line matching structure, and metal electrodes are provided between the coplanar waveguide metal ground and the microstrip line matching structure; the composite beam MEMS switch is mounted on the top of the microstrip line matching structure;

[0037] The composite beam MEMS switch includes an upper beam and a lower beam; the lower beam is hollowed out at the middle position of the upper beam, an intermediate conduction structure is provided at the middle position of the upper beam, and the intermediate conduction structure is located directly above the gap of the microstrip line matching structure; two metal electrodes of the composite beam MEMS switch are respectively located below the left arm and the right arm of the lower beam; the left arm and the right arm of the lower beam and the two metal electrodes are connected to the DC port metal block on the same side through corresponding DC bias lines.

[0038] The upper beam of the composite beam MEMS switch is made of silicon dioxide.

[0039] The material of the lower beam of the composite beam MEMS switch is gold.

[0040] The middle conducting structure of the composite beam MEMS switch is an H-shaped metal sheet with four cylindrical contacts distributed under the metal sheet.

[0041] The upper beam of the composite beam MEMS switch is a symmetrical figure with an H-shaped structure as the middle line, including a left bridge pier, a left connecting arm, a left actuating arm, a left middle arm, an H-shaped structure, a right middle arm, a right actuating arm, a right connecting arm and a right bridge pier connected from left to right; the connecting arm is a folded and curved ridge structure, and periodic circular holes are corroded on both the left actuating arm and the right actuating arm.

[0042] The lower beam of the composite beam MEMS switch includes a left arm portion, a left hollow portion, an H-shaped structure, a right hollow portion and a right arm portion; the left arm portion and the right arm portion are symmetrical to each other; both the left arm portion and the right arm portion include an outer folded and bent volute structure and an inner action arm; the inner action arm is etched with periodic circular holes.

[0043] The left-side and right-side volute structures of the composite beam MEMS switch have the same size as the outer-side volute structure, and the left-side and right-side volute structures are respectively opposite to the outer-side volute structure on the same side in upper and lower positions; the left-side action arm, the right-side action arm and the inner action arm have the same size, and the left-side and right-side action arm are respectively opposite to the inner-side action arm on the same side in upper and lower positions.

[0044] The microstrip line matching structure is composed of input and output trapezoidal gradient microstrip lines for matching. The middle conduction structure of the composite beam MEMS switch is located directly above the trapezoidal gradient microstrip line structures on both sides, and conduction is achieved when pulled down.

[0045] Attach Figure 1 -Attached Figure 8 Taking a low-driving-voltage terahertz-band composite beam RF MEMS switch as an example, this embodiment includes DC port metal blocks 1, 2, DC bias lines 3, 4, 5, 6, 7, 8, 9, 10 microstrip line matching structure 11, and a composite beam MEMS switch 15 consisting of an upper beam 23, a lower beam 24, a composite beam intermediate conductive structure 25, metal electrodes 19, 20 of the composite beam, silicon nitride insulating layers 21, 22 on the upper surface of the composite beam metal electrodes, a quartz glass substrate 16, a coplanar waveguide metal ground 12, and a metal ground 26; since silicon dioxide has a lower Poisson's ratio than conventional metals and is not easy to undergo plastic deformation, the composite beam is a fixed beam composed of a silicon dioxide upper beam 23, a metal lower beam 24 adsorbed thereunder, and an intermediate conductive structure 25. The metal lower beam and the metals distributed on both sides below the metal lower beam serve as upper and lower electrodes, and are connected to the DC port metal blocks 1, 2 through DC bias lines 3, 4, 5, 6, 7, 8, 9, 10, respectively.

[0046] The dielectric constant of the quartz glass substrate 16 is 3.78 and the thickness is 100 um.

[0047] Composite beam MEMS switch disconnected state, as shown in the attached Figure 3, the DC port metal blocks are grounded or at the same voltage, so that the composite beam MEMS switch does not produce longitudinal deformation as a whole, and the microstrip line matching structure 11 is kept in a disconnected state; if the composite beam MEMS switch is to be turned on, as shown in the attached Figure 4 , the metal lower beam and the metal electrode are grounded and driven by the DC port metal block. The driving voltage generates an electrostatic force between the metal electrode and the metal lower beam, so that the metal lower beam 24 drives the silicon dioxide upper beam 23 to produce longitudinal deformation, pulling the composite beam downward as a whole, and finally making the contact point below the intermediate conductive structure 25 contact with the upper part of the disconnected part of the microstrip line matching structure 11, forming a conductive state.

[0048] As attached Figure 5 As shown, the composite beam upper beam 23 is a symmetrical structure, which is composed of rectangular structures of different sizes including piers 35, connecting arms 36, 37, action arms 34, middle arms 38, and H-shaped structures 40. The connecting arms are folded and bent ridge structures, and the action arms 34 are corroded with periodic cylindrical holes.

[0049] As attached Figure 6 As shown, the metal lower beam 24 of the composite beam is a symmetrical structure, including symmetrical piers 44, connecting arms 45, 46 and action arms 43. The action arms 43 are corroded with periodic cylindrical holes, and the sizes of 44, 45, 46 and 43 are exactly the same as those of structures 35, 36, 37, and 34.

[0050] The structural design of the upper beam 23 and the lower beam 24 is intended to reduce the pull-down driving voltage, shorten the response time, reduce the residual stress, and achieve high-speed and reliable switch performance. In this embodiment, the driving voltage can be controlled at 15-25V.

[0051] As attached Figure 7 As shown, the composite beam intermediate conducting structure 25 is an H-shaped metal sheet, and two cylindrical contacts are distributed on both sides of the metal sheet, which is attached to the center of the silicon dioxide upper beam 23. The purpose of the structural design is to increase the isolation of the switch and reduce the insertion loss of the switch.

[0052] As attached Fig. 9 and attached Fig.10 They are the return loss S when the switch is off and on respectively. 11 and S 21 Performance scattering parameter curves.

[0053] The size parameters of the intermediate conduction structure and the microstrip line matching structure will affect the RF performance of the switch. The size of the composite beam and the metal electrode will affect the performance of the driving voltage, which is mainly manifested as follows:

[0054] A. The narrower the overall width of the intermediate conduction structure, the better the isolation of the switch in the off state. At the same time, an H-shaped structure is adopted to adjust the detail size and optimize the isolation.

[0055] B. The longer the overall width of the switch and the longer the disconnect length of the microstrip line matching structure, the better the switch isolation, but it will increase the overall structure size of the switch and affect the layout and use.

[0056] C. The size of the microstrip line matching structure will affect the switching loss characteristics when the switch is in the on state. This design adopts a gradient structure from the microstrip line width to the conduction structure width, which is beneficial to reduce the insertion loss when the switch is in the on state.

[0057] D. The size of the silica beam and the metal beam mainly affects the performance such as driving voltage and response time. This design adopts a clamp-shaped arm structure with a hollow middle and continuously optimizes the size of the connecting arm, the action arm and the H-shaped structure to stabilize the working voltage of the driving voltage between 15-25V and the response time in microseconds.

[0058] E. The size and spacing of the periodic cylindrical holes will affect the magnitude of the electrostatic force between the metal electrode and the beam, and thus will also affect the working voltage of the driving voltage.

[0059] Therefore, choosing the appropriate composite beam size, composite beam conduction structure size, and microstrip line matching structure size is crucial to improving the overall switch performance.

[0060] The following selects a size combination to introduce the size of the structure in the attached figure. The following data is in micrometers;

[0061] Attached Figure 3 The dimensions of the structure are:

[0062] The thickness of the upper beam, i.e. the length of reference numeral 27, is 1; the thickness of the lower beam, i.e. the length of reference numeral 28, is 0.5; the thickness of the H-shaped structure, i.e. the length of reference numeral 29, is 0.5; the thickness of the cylindrical contact, i.e. the length of reference numeral 30, is 0.2; the thickness of the microstrip line matching structure, i.e. the length of reference numeral 31, is 1;

[0063] As attached Figure 5 , attached Figure 6 As shown, the dimensions of the structure are:

[0064] The width of the upper beam and the width of the lower beam, i.e. the lengths of reference numerals 32 and 41, are both 90; the width of the gap, i.e. the lengths of reference numerals 33 and 42, are both 75; the width of the action arm, i.e. the lengths of reference numerals 34 and 43, are both 50;

[0065] The length of the piers, i.e., the lengths of numbers 35 and 44, are both 20; the length of the connecting arms, i.e., the lengths of numbers 36 and 45, is 5, and the lengths of numbers 37 and 46 is 35; the length of the middle arm, i.e., the length of number 38, is 15; the length of the H-shaped structure, i.e., the length of number 40, is 20; the length of the H-shaped structure branch, i.e., the length of number 39, is 8.

[0066] Attached Figure 7 The dimensions of the structure are:

[0067] The width of the H-shaped structure, i.e., the length of label 49, is 68; the width of the branch of the H-shaped structure, i.e., the length of label 48, is 24; the length of the distance between the branches on both sides of the H-shaped structure, i.e., the length of label 47, is 4; the diameter of the cylindrical contact, i.e., the length of label 50, is 5.

[0068] The thickness of the quartz glass substrate is 100; the thickness of the metal layer of the microstrip line and the metal ground is 1; the thickness of the silicon nitride insulating layer is 0.1; under this structural size, when the switch works at 140GHz, it can ensure that the isolation in the off state is higher than 20dB; the insertion loss in the on state is lower than 0.7dB.

[0069] Attached Figure 8 It is a three-dimensional image of the overall structure of the composite beam RF MEMS switch.

[0070] When the switch is in the off state, the return loss S 11 , Isolation S 21 The curve is as follows Fig. 9 As shown, it can be seen that the return loss S11 of the switch is higher than -3.8dB and the isolation S21 is between -10.6dB and -28.1dB in the range of 120-160GHz.

[0071] When the switch is in the on state, the return loss S 11 , Insertion loss S 21 The curve is as follows Fig.10 As shown, it can be seen that the return loss S11 of the switch is lower than -10dB and the insertion loss S21 is significantly higher than -1dB in the range of 120-160GHz.

[0072] The switch has a driving voltage of 15-25V and a response speed of microseconds.

[0073] In summary, the composite beam MEMS switch proposed in the present invention can be integrated into a microstrip line or a coplanar waveguide transmission line, and has good isolation and loss characteristics in the terahertz band.

[0074] The above is just an example. If you want to obtain a MEMS switch that works at different frequencies, you can design different switch sizes for application in different scenarios.

Claims

1. A low-drive-voltage terahertz-band composite beam RF MEMS switch, comprising a quartz glass substrate (16), a coplanar waveguide metal ground (12) and a metal ground (26); the coplanar waveguide metal ground (12) is located on the upper surface of the quartz glass substrate; the metal ground (26) is located on the lower surface of the quartz glass substrate; characterized in that: The upper surface of the quartz glass substrate is also provided with a DC port metal block, a DC bias line, a microstrip line matching structure (11) and a composite beam MEMS switch; Wherein, the microstrip line matching structure and the composite beam MEMS switch (15) are both located in an area surrounded by the coplanar waveguide metal ground; The DC port metal blocks are provided with two and are respectively located on two sides outside the coplanar waveguide metal ground area; the composite beam MEMS switch (15) is mounted directly above the middle position of the microstrip line matching structure (11); the metal electrodes and bridge piers of the composite beam MEMS switch (15) are connected to the corresponding DC port metal blocks via a DC bias line.

2. The low-driving-voltage terahertz-band composite beam RF MEMS switch according to claim 1, characterized in that: The composite beam MEMS switch (15) comprises an upper beam (23) and a metal lower beam (24) which are stacked, wherein the metal lower beam is located on the lower surface of the upper beam; the metal lower beam (24) at the middle position of the upper beam (23) is hollowed out, and an intermediate conductive structure (25) of the metal lower beam is located at the middle position of the upper beam (23), and the intermediate conductive structure (25) is located directly above the notch of the microstrip line matching structure (11); The two metal electrodes are respectively located directly below the left action arm and the right action arm of the lower beam (24); wherein the two metal electrodes are connected to the DC port metal block (1) on the left side through corresponding DC bias lines.

3. The low-driving-voltage terahertz-band composite beam RF MEMS switch according to claim 2, characterized in that: The material of the upper beam (23) of the composite beam MEMS switch (15) is silicon dioxide.

4. The low-driving-voltage terahertz-band composite beam RF MEMS switch according to claim 2, characterized in that: The material of the lower beam (24) of the composite beam MEMS switch (15) is gold.

5. The low-driving-voltage terahertz-band composite beam RF MEMS switch according to claim 2, characterized in that: The middle conducting structure (25) of the composite beam MEMS switch (15) is an H-shaped metal sheet, and four cylindrical contacts are distributed below the H-shaped metal sheet.

6. The low-driving-voltage terahertz-band composite beam RF MEMS switch according to claim 2, characterized in that: The upper beam (23) of the composite beam MEMS switch (15) is a symmetrical figure with the upper beam H-shaped structure as the middle line, comprising a left bridge pier, a left connecting arm, a left action arm, a left middle arm, an upper beam H-shaped structure, a right middle arm, a right action arm, a right connecting arm and a right bridge pier connected in sequence from left to right; Among them, the bridge piers are connected to the metal lower beams; The connecting arm is a folded and curved volute structure, and periodic circular holes are etched on both the left and right action arms.

7. The low-driving-voltage terahertz-band composite beam RF MEMS switch according to claim 2, characterized in that: The metal lower beam (24) of the composite beam MEMS switch (15) comprises a left arm portion, a left hollow portion, a lower beam H-shaped structure, a right hollow portion and a right arm portion; wherein the left arm portion and the right arm portion are symmetrical to each other; the left arm portion and the right arm portion both comprise a line-connected outer folded and bent meandering structure and an inner action arm; and the inner action arm is etched with periodic circular holes.

8. The low-driving-voltage terahertz-band composite beam RF MEMS switch according to claim 1, characterized in that: The microstrip line matching structure (11) is composed of input and output trapezoidal gradient microstrip lines and is used for matching. The middle conduction structure (25) of the composite beam MEMS switch (15) is located directly above the trapezoidal gradient microstrip line structures on both sides and is turned on when pulled down.

9. The low-driving-voltage terahertz-band composite beam RF MEMS switch according to claim 1, characterized in that: The upper surface of the metal electrode of the composite beam MEMS switch (15) is provided with a silicon nitride insulating layer.

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