CN102243940B - Buckling radio frequency micro switch by using folded beams - Google Patents

Abstract

The invention discloses a folded beam buckling radio frequency micro switch, which mainly solves the problems of high driving voltage, long response time, high loss and the like of the existing switch. The invention comprises: adjusting electrode pairs (31, 32), fixed base (33), driving electrode pairs (34, 35) and outer frame (39), wherein: the inner wall of the outer frame (39) is consolidated with microbeams (36) and folded beam (38), the folded beam (38) adopts a plurality of rectangular bending structures, the microbeam (36) adopts a vertical and horizontal bending buckling deformation structure, and the folded beam (38) is located at the two ends of the microbeam (36), and It has an integrated structure; the two ends of the fixed base (33) and the outer frame (39) are provided with a guide mechanism (37); the adjusting electrode pairs (31, 32) adopt a comb-like structure, and are symmetrical up and down. The invention has the advantages of low voltage, high frequency response, high isolation and low loss, and can be used in radio frequency transceiver circuits, microwave integrated circuits, radar antenna T/R components, and radio frequency duplex circuits.

Description

Polybeam Buckling RF Micro Switch

technical field

The invention belongs to the technical field of electronic devices, in particular to a radio frequency micro switch, which can be used in the fields of microwave integrated circuits, radio frequency transceiver circuits, radar antenna T/R components and the like.

technical background

Buckling RF micro-switches are processed by micro-mechanical technology. Based on the theory of longitudinal and horizontal bending of folded beams, they break through the traditional concept of unidirectional loading of RF micro-switches, and use the elastic energy release and stiffness changes of folded beams during buckling deformation to show The jump feature transforms the elastic force into a driving force to achieve the purpose of high isolation, low loss, low voltage and high frequency response of RF micro-switches. It has the characteristics of small size, high reliability, and simple structure, so it has a strong demand in the fields of radio frequency transceiver circuits, microwave integrated circuits, radar antenna T/R components, and radio frequency duplex circuits.

In 2008, MEMS Key Laboratory of Southeast University [Analysis of pull-in voltage of RF MEMS switch, Dong Qiaohua, Liao Xiaoping, Huang Qingan, Huang Jianqiu, Key Laboratory of MEMS Ministry of Education, Southeast University, Journal of Semiconductors, Volume 29, Issue 1, 2008 1 Month, 163-169] proposed a radio-frequency microswitch actuated by electrostatic force with both ends consolidated, as shown in Figure 1. The microbeam 11 is fixed by the fixing point 12 and suspended above the ground plane 13 and the signal plane 14 , and the external circuits are respectively connected to the microbeam 11 and the signal plane 14 . When a voltage is applied between the microbeam 11 and the signal board 14 , the microbeam 11 moves downward under the action of electrostatic force and contacts the signal board 14 , thereby realizing the closure between the external circuits. This RF switch has the following problems:

1) Since a high voltage of 33V needs to be applied between the microbeam 11 and the signal board 14, there is a danger of ablation of the switch.

2) The gap between the microbeam 11 and the signal board is too small, resulting in too low isolation of the radio frequency switch.

In 2010, the San Diego branch of the University of California in [Rashed Mahameed, Gabriel M. Rebeiz, Electrical and Computer Engineering Department, University of California at San Diego, A High-Power Temperature-Stable Electrostatic RF MEMS Capacitive Switch Based on a UBermRNAL Thermal Buckle, OBermRNALuckle-J OFMICROELECTROMECHANICAL SYSTEMS, VOL.19, NO.4, 2010, 816-826] proposed an electrostatically driven thermal buckling high-power RF switch, as shown in Figure 2. The anchor point 23 of this radio frequency switch is fixed on the fixed point 25, and the upper plate 21 is connected to the anchor point 23 through the microbeam 22. The upper pole plate 21 and the lower pole plate 24 are connected with an external circuit. When the external voltage acts on the micro-beam 22, the micro-beam 22 expands and buckles due to heat, the upper plate 21 moves downward and contacts the lower plate 24, the external circuit is turned on, and the switch is closed.

Although this structure improves the isolation of the RF switch, there are the following problems:

1) The driving voltage is too high, reaching 40V.

2) The response time is too long and the switching frequency is too low.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art, and provide a folded beam buckling radio frequency micro switch to reduce the driving voltage and increase the response frequency.

In order to achieve the above object, the micro switch of the present invention includes: adjusting electrode pair, fixed base, driving electrode pair and outer frame, wherein: the inner wall of the outer frame is consolidated with microbeam and folded beam; There is a guiding mechanism, which is used to limit the left and right swing of the microbeam; the adjustment electrode pair adopts a comb-like structure.

The micro-beam and folded beam are integrally structured, and the folded beam is located at both ends of the micro-beam. The folded beam adopts a plurality of rectangular bending structures to reduce the stiffness of the folded beam; the micro-beam adopts a longitudinal and transverse bending buckling deformation structure to realize low pressure and large deformation drive.

The present invention has the following advantages:

1) the present invention is owing to be consolidated with micro-beam and folded beam on the inner wall of outer frame, the ratio of the total axial length L ' of micro-beam and folded beam and the inner wall length L of outer frame is 101: 100, makes micro-beam and folded beam The beam pre-acquires the axial compressive buckling potential energy, thus reducing the driving voltage;

2) In the present invention, since the adjusting electrode pair adopts a comb-like structure, the voltage of the adjusting electrode can be adjusted so that the microbeam reaches the Euler critical load before deformation and is in a state of "micro-bending balance", thereby reducing the driving voltage;

3) The present invention reduces the rigidity of the folded beam because the folded beam adopts a plurality of rectangular bending structures, thereby reducing the driving voltage and improving the response frequency;

4) The present invention breaks through the traditional concept of unidirectional loading by adopting the micro-beam vertical and horizontal bending buckling deformation structure, reduces the driving voltage and deformation time, realizes low-voltage and large-deformation driving of the micro-switch, and improves the response frequency;

5) Since the present invention is provided with guide mechanisms at both ends of the fixed machine base, the left and right swing of the micro-beam is limited, thereby ensuring that the deformation of the folded beam is symmetrical;

6) Compared with other existing micro-switches, the micro-switch of the present invention has fewer components and uses silicon material, which is low in cost and easy to process and realize.

Description of drawings

Fig. 1 is the structural diagram of the existing two-end consolidated radio frequency micro-switch;

Fig. 2 is the structural diagram of the existing constant-temperature electrostatically driven buckling type radio frequency micro-switch;

Fig. 3 is a structure diagram of a buckling radio frequency micro-switch of a folded beam according to the present invention.

Detailed ways

With reference to Fig. 3, microswitch of the present invention is mainly made of regulating electrode pair 31 and 32, fixed support 33, drive electrode pair 34 and 35, detection electrode pair 38 and 39, microbeam 36, folding beam 38, guide mechanism 37 and outer The framework 39 is composed, and the whole structure is symmetrical up and down, and the material is silicon material.

The micro-beam 36 and the polybeam 38 are integrated structures, and the polybeam 38 is located at both ends of the micro-beam 36 , and the polybeams 38 at both ends adopt a plurality of rectangular curved structures, which are symmetrical up and down to reduce the rigidity of the polybeam. The micro-beam 36 and folded beam 38 are consolidated on the inner wall of the outer frame 39 by pressure welding, and the micro-beam 36 adopts a vertical and horizontal bending buckling deformation structure to realize low pressure and large deformation driving. By rationally designing the ratio of the total axial length L' of the micro-beams 36 and folded beams 38 to the length L of the inner wall of the outer frame 39 to be 101:100, the micro-beams 36 and folded beams 38 can obtain axial extrusion force in advance. The adjusting electrode pairs 31 and 32 adopt a comb-like structure, fixed on the microbeam 36, and are symmetrical up and down. The adjustment electrode pair 31 and 32 are connected to the external adjustment circuit by pressure welding, and through the adjustment of the external adjustment circuit, the two ends of the microbeam 36 are synchronously controlled, so that the microbeam 36 and the folded beam 38 reach the Euler critical load and maintain " Micro-bending balance” state, while avoiding the micro-beam 36 being in a loaded state for a long time, reducing the risk of micro-beam fracture, and prolonging the service life of the micro-switch.

The guiding mechanism 37 is fixed on both ends of the fixed base 33 and the outer frame 39, and is used to limit the left and right swing of the micro-beam 36, ensure that the buckling deformation of the folded beam 38 is symmetrical, and avoid secondary buckling deformation. The pair of driving electrodes 34 and 35 is formed by the gold film deposited on the right side of the middle part of the fixed base 33 and the left side of the microbeam 36. The pair of driving electrodes 34 and 35 are connected to the external regulation circuit by pressure welding. A driving voltage is applied to the pair of driving electrodes 34 and 35 , so as to generate a transverse force to realize longitudinal and transverse bending and buckling deformation of the microbeam 36 . The present invention breaks through the current traditional concept of one-way loading of micro-switches, utilizes the “snap jump” characteristic exhibited by the combined deformation of micro-beams and folded beams due to the energy release and stiffness changes, so that the stored axial potential energy is quickly released, and the elastic force is transformed into as the driving force. A gold film is deposited on the left side surface of the outer frame 39 as a fixed detection electrode 40 , and a gold film is deposited on the right side of the microbeam 36 as a movable detection electrode 41 . When the microbeam 36 and folded beam 38 reach the Euler critical load, the state of "microbending balance" is maintained, and the driving voltage is applied to the driving electrode pair 34 and 35, thereby generating a lateral force to realize the large deformation of the microbeam 36 in vertical and horizontal bending buckling, so that The movable detection electrode 41 is in contact with the fixed detection electrode 40 to complete the connection function between the detection electrode and the external circuit, thereby realizing the requirements of high isolation, low loss, high frequency and low driving voltage of the radio frequency micro-switch.

The working principle of the present invention is as follows:

In the non-working state, the voltage across the adjusting electrode pair 31 and 32 is 0, the voltage across the driving electrode pair 34 and 35 is 0, the microbeam 36 is in a straight line state, and the folded beam 38 fixed on the outer frame 39 is subjected to axial force. Preload. Due to the limit of the upper and lower guide mechanism 37, it is ensured that the micro-beam 36 is in a vertical straight line state, and the micro-switch remains disconnected, as shown by the solid line in FIG. 3 .

In the working state, the voltage at both ends of the electrode pair 31 and 32 is adjusted through the external adjustment circuit, so that the axial load of the microbeam 36 reaches the Euler load critical value, and the microbeam 36 is in the state of "microbending balance", and then the external drive The circuit applies a driving voltage to both ends of the driving electrodes 34 and 35. Since the microbeam 36 is already in the state of “microbending equilibrium”, the electric field force generated by the very small driving voltage at this time will cause the microbeam 36 to produce a rapid movement to the right. The large buckling deformation makes the movable detection electrode 41 contact with the fixed detection electrode 40, and the micro switch is in the closed state to realize the connection of the external detection circuit, as shown by the dotted line in FIG. 3 .

Claims (4)

1. A folded beam buckling radio frequency microswitch, comprising: adjusting electrode pairs (31, 32), fixing base (33), driving electrode pairs (34, 35) and outer frame (39), characterized in that: the fixing machine The two ends of the seat (33) and the outer frame (39) are provided with a guide mechanism (37), which is used to limit the left and right swing of the micro-beam; the inner wall of the outer frame (39) is fixed with a micro-beam (36) and a folded beam ( 38), the micro-beam (36) and folded beam (38) are integrated, and the folded beam (38) is located at both ends of the micro-beam (36); the adjustment electrode pair (31, 32) adopts a comb-like structure, fixed On the micro-beam (36), and symmetrical up and down; The folded beam (38) adopts a plurality of rectangular bending structures to reduce the rigidity of the folded beam, and the micro-beam (36) adopts a vertical and horizontal bending buckling deformation structure to realize low pressure and large deformation driving; the micro-beam (36) and the folded beam ( The ratio of the total axial length L' of 38) to the length L of the inner wall of the outer frame (39) is 101:100, so that the microbeams (36) and polybeams (38) are consolidated on the outer frame (39) by pressure welding inner wall, to obtain axial extrusion force. the 2. The radio frequency micro-switch according to claim 1, characterized in that a gold film layer is deposited on the left side of the microbeam (36) and the right side surface of the fixed base (33), and the two gold film layers form the driving electrodes (34, 35), the driving electrode is connected to the external driving circuit by pressure welding. the 3. The radio frequency micro-switch according to claim 1, characterized in that the fixed base (33), the outer frame (39), the micro-beams (36) and the folded beams (38) are all silicon materials. the 4. The radio frequency micro switch according to claim 1, characterized in that the adjustment electrode pair (31, 32) is connected to the external adjustment circuit by pressure welding, and is controlled synchronously to ensure that the microbeam (36) maintains "microbending balance" state. the

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