MEMS millimeter wave switches
View Patent ↗An RF switch useable up to millimeter wave frequencies and higher frequencies of 30 GHz and above. Four embodiments of the invention are configured as ground switches. Two of the ground switch embodiments are configured with a planar air bridge. Both of these embodiments are configured so that the bridge length is shortened between the transmission line and ground by introducing grounded stops. The other two ground switch embodiments include an elevated metal seesaw. In these embodiments, a shortened path to ground is provided with relatively low inductance by proper sizing and positioning of the seesaw structure. Lastly, broadband power switch embodiment is configured to utilize only a small portion of the air bridge to carry the signal. The relatively short path length results in a relatively low inductance and resistance lowers the RF power loss of the switch, thereby increasing the RF power handling capability of the switch.
1. A ground switch for use in millimeter wave applications, the grounding switch comprising:
a transmission line defining an RF input and an RF output at opposing ends;
an RF contact formed on said transmission line;
one or more ground contacts adapted to be connected to ground, spaced apart from said transmission line and an air bridge, for grounding said transmission line;
an air bridge beam formed adjacent said transmission line, said air bridge beam rigidly connected to a substrate at each end, said beam spaced away from said RF contact and said one or more ground contacts in an at rest position and configured to contact said RF contact and said one or more ground contacts in an actuated position; and
one or more control pads disposed adjacent said transmission line, said one or more control pads adapted to receive biasing voltage to cause said beam to deflect to said actuated position.
2. The ground switch as recited in claim 1 , wherein said air bridge is generally transverse to said transmission line.
3. The ground switch as recited in claim 2 , wherein said RF ground contact is formed on said transmission line.
4. The ground switch as recited in claim 3 , wherein said air bridge beam is formed above said transmission line.
5. The ground switch as recited in claim 4 , wherein said one or more ground contacts are formed on the same side of said air bridge beam as said RF contact.
6. The ground switch as recited in claim 1 , wherein said air bridge beam is generally parallel to said transmission line.
7. The ground switch as recited in claim 6 , wherein said RF contact and said one or more ground contacts are formed on opposing sides of said air bridge beam.
8. The ground switch as recited in claim 1 , wherein at least two or more control pads are provided.
9. The ground switch as recited in claim 8 , wherein said control pads are formed on one side of said air bridged beam.
10. The ground switch as recited in claim 8 , wherein said control pads are formed on both sides of said air bridged beam.
11. An RF switch for use in millimeter wave applications, the RF switch comprising:
a substrate;
a plurality of transmission lines carried by said substrate defining at least one input transmission line and at least two output transmission lines;
a respective RF contact formed on each of said plurality of transmission lines;
one or more movable metal layers carried by the substrate, each of said one or more movable metal layers formed adjacent said plurality of transmission lines, each one of said movable metal layers spaced away from said plurality of transmission lines in a rest position and formed to be in electrical contact with various ones of said RF contacts on said plurality of transmission lines in an actuated position forming a single pole double throw broadband switch, said one or more movable metal layers being responsive to electrostatic forces and moving to said actuated position in response to said electrostatic forces and returning to said rest position when said electrostatic forces are removed, whereby said one or more movable metal layers are configured to move in a direction generally parallel to a plane of said plurality of transmission lines; and
one or more control pads disposed adjacent said plurality of transmission lines, said one or more control pads adapted to receive biasing voltage to cause said one or more metal layers to move to said actuated position.
12. The RF switch as recited in claim 11, wherein said one or more movable metal layers are configured as deflectable air bridge beams, formed over said input and output transmission lines and configured to contact said various ones of said RF contacts in said actuated position and configured to be spaced away from said RF contacts in said rest position.