MEMS switch for RF applications
Microelectromechanical systems (MEMS) switches are disclosed. Parallel configurations of back-to-back MEMS switches are disclosed in some embodiments. An isolation connection of constant electrical potential may be made to a midpoint of the back-to-back switches. In some embodiments, a separate MEMS switch is provided as a shunt switch for the main MEMS switch. MEMS switch device configurations having multiple switchable signal paths each coupling a common input electrode to a respective output electrode are also disclosed. The MEMS switch device includes shunt switches each coupling a respective output electrode to a reference potential. The presence of a shunt switch coupled to an output electrode enhances the isolation of the signal path corresponding to that output electrode when the path is open.
1 . A microelectromechanical systems (MEMS) switch device, comprising:
a first signal path comprising a first MEMS switch and a second MEMS switch in a back-to-back configuration with the first MEMS switch; and
a second signal path comprising a third MEMS switch and a fourth MEMS switch in a back-to-back configuration with the third MEMS switch,
wherein the first signal path is electrically coupled between a first and second electrode and the second signal path is electrically coupled, separately from the first signal path, between the first electrode and the second electrode, and wherein the first MEMS switch is a first teeter-totter switch comprising a mid-beam anchor and a first gate electrode, the second MEMS switch is a second teeter-totter switch comprising a mid-beam anchor and a second gate electrode, and the first gate electrode is coupled to the second gate electrode.
2 . The MEMS switch device of claim 1 , further comprising:
a middle electrode electrically connected between the first MEMS switch and the second MEMS switch; and
an isolation stub configured to connect the middle electrode to a reference potential.
3 . The MEMS switch device of claim 1 , further comprising:
a shunt switch coupling the first electrode to a reference potential.
4 . The MEMS switch device of claim 1 , further comprising:
a third signal path comprising a fifth MEMS switch and a sixth MEMS switch in a back-to-back configuration with the fifth MEMS switch; and
a fourth signal path, separate from the third signal path, comprising a seventh MEMS switch and an eighth MEMS switch in a back-to-back configuration with the seventh MEMS switch,
wherein the third signal path is electrically coupled between the first electrode and a third electrode and the fourth signal path is electrically coupled between the first electrode and the third electrode.
5 . A microelectromechanical systems (MEMS) switch device, comprising:
first, second and third electrodes, wherein a first signal path is disposed between the first and second electrodes and a second signal path is disposed, separately from the first signal path, between the first and third electrodes;
a first MEMS switch electrically coupled between the first and second electrodes and forming a portion of the first signal path when the first MEMS switch is closed;
a second MEMS switch electrically coupled between the first and third electrodes and forming a portion of the second signal path when the second MEMS switch is closed; and
a first shunt switch electrically coupled between the third electrode and a reference potential.
6 . The MEMS switch device of claim 5 , wherein the second MEMS switch and the first shunt switch are part of a teeter-totter switch having a mid-beam anchor, so that:
when the teeter-totter switch is in a first state, the second MEMS switch is closed and the first shunt switch is open, and
when the teeter-totter switch is in a second state, the second MEMS switch is open and the first shunt switch is closed.
7 . The MEMS switch device of claim 5 , wherein the first shunt switch is electrically coupled to the reference potential by either a conductive pillar and/or a conductive bump.
8 . The MEMS switch device of claim 5 , wherein the first shunt switch is electrically coupled to the reference potential by a half wave stub.
9 . The MEMS switch device of claim 5 , wherein the first shunt switch is electrically coupled to the reference potential by a bond wire.
10 . The MEMS switch device of claim 9 , wherein the bond wire forms a quarter wave or half wave stub.
11 . The MEMS switch device of claim 5 , further comprising a controller configured to concomitantly close both the first MEMS switch and the first shunt switch.
12 . The MEMS switch device of claim 11 , wherein the controller is further configured to, concomitantly with closing the first MEMS switch, open the second MEMS switch.
13 . The MEMS switch device of claim 12 , further comprising a second shunt switch electrically coupled between the second electrode and the reference potential.
14 . The MEMS switch device of claim 13 , wherein the controller is further configured to, concomitantly with closing the first MEMS switch, open the second shunt switch.
15 . A microelectromechanical systems (MEMS) switch device, comprising:
first, second and third electrodes, wherein a first signal path is disposed between the first and second electrodes and a second signal path is disposed between the first and third electrodes;
a first MEMS switch electrically coupled between the first and second electrodes and forming a portion of the first signal path when the first MEMS switch is closed;
a second MEMS switch electrically coupled between the first and third electrodes and forming a portion of the second signal path when the second MEMS switch is closed;
a first shunt switch electrically coupled between the third electrode and a reference potential; and
an inductor/capacitor (LC) circuit coupled between the third electrode and the reference potential.
16 . The MEMS switch device of claim 15 , wherein the LC circuit comprises a vertical capacitor having first and second terminals, wherein the first terminal is formed on a pad that is connected to a wire bond and that lies on a first plane, and the second terminal lies on a second plane parallel to the first plane.
17 . A method for operating a microelectromechanical systems (MEMS) switch device comprising a first MEMS switch coupling a first electrode to a second electrode, a second MEMS switch coupling the first electrode to a third electrode, and a first shunt switch coupling the third electrode to a reference potential, the method comprising:
forming a first signal path between the first electrode and the second electrode by closing the first MEMS switch, wherein the first MEMS switch is a first teeter-totter switch comprising a mid-beam anchor;
concomitantly with closing the first MEMS switch, forming a first shunt path between the third electrode and the reference potential by closing the first shunt switch; and
concomitantly with closing the first MEMS switch, interrupting a second signal path between the first electrode and the third electrode by opening the second MEMS switch.
18 . The method of claim 17 , wherein the MEMS switch device further comprises a second shunt switch coupling the second electrode to the reference potential, and wherein the method further comprises:
concomitantly with closing the first MEMS switch, interrupting a second shunt path between the second electrode and the reference potential by opening the second shunt switch.
19 . The method of claim 17 , wherein the second MEMS switch and the first shunt switch are part of a common teeter-totter switch, and wherein:
opening the first shunt switch and closing the second MEMS switch collectively comprise switching the teeter-totter switch from a first state to a second state.
20 . The method of claim 17 , wherein opening the second MEMS switch includes wherein the second MEMS switch includes a teeter-totter switch comprising a mid-beam anchor.