ELECTROSTATIC DAMPING OF MEMS DEVICES
The present invention generally relates to a method and apparatus for damping a plate electrode or switching element in a MEMS DVC device. A resistor disposed between a waveform controller and the electrodes of the MEMS DVC causes the voltage to increase while capacitance decreases during the time that the plate electrode is moving. Due to the increase in voltage and decrease in capacitance, the electrostatic force that resists the plate electrode movement away from an electrode increases, which in turn dampens the movement of the plate electrode.
1 . A device, comprising:
a MEMS device comprising:
a plate electrode;
the first electrode;
a first dielectric layer disposed over the first electrode;
a second electrode disposed opposite the first electrode; and
a second dielectric layer disposed over the second electrode such that the plate electrode is movable between a first position in contact with the first dielectric layer, a second position in contact with the second dielectric layer, and a third position spaced from both the first and second dielectric layers;
a waveform controller coupled to the first electrode and the second electrode; and
a first resistor coupled between the first electrode and the waveform controller.
2 . The device of claim 1 , further comprising a second resistor coupled between the second electrode and the waveform controller.
3 . The device of claim 2 , wherein the resistance of the second resistor times the capacitance of the second electrode is larger than the dynamic response time of the plate electrode.
4 . The device of claim 2 , wherein the resistance of the first resistor times the capacitance of the first electrode is larger than a dynamic response time of the plate electrode.
5 . The device of claim 4 , wherein the resistance of the second resistor times the capacitance of the second electrode is larger than the dynamic response time of the plate electrode.
6 . The device of claim 1 , wherein the resistance of the first resistor times the capacitance of the first electrode is larger than a dynamic response time of the plate electrode.
7 . A method of operating a MEMS device, comprising:
reducing a voltage applied to a first electrode of the MEMS device to zero, wherein the MEMS device comprises the first electrode, a second electrode and a plate electrode movable from a first position disposed adjacent the first electrode and a second position disposed adjacent the second electrode;
reducing a capacitance of the first electrode;
applying a voltage to the second electrode, wherein the voltage is applied to the second electrode either:
while reducing the capacitance of the first electrode; or
after the capacitance of the first electrode has decreased;
increasing the voltage applied to the second electrode;
moving the plate electrode from the first position to the second position;
increasing a capacitance of the second electrode during the moving; and
decreasing the capacitance of the first electrode during the moving.
8 . The method of claim 7 , wherein the plate electrode vibrates during the moving.
9 . The method of claim 8 , wherein the vibrating decreases as the plate electrode moves from the first position to the second position.
10 . The method of claim 9 , wherein during the reducing the capacitance of the first electrode, the voltage applied to the first electrode increases and wherein electrostatic force at the plate electrode increases while the voltage applied to the first electrode increases.
11 . The method of claim 7 , wherein applying the voltage to the second electrode occurs while the reducing the capacitance of the first electrode, and wherein the voltage applied to the first electrode increases.
12 . The method of claim 11 , wherein electrostatic force at the plate electrode increases while the voltage applied to the first electrode increases.
13 . The method of claim 7 , wherein applying the voltage to the second electrode occurs after the capacitance of the first electrode has discharged, and wherein the voltage applied to the first electrode increases.
14 . A method of operating a MEMS device, comprising:
reducing a voltage applied to a first electrode of the MEMS device to zero, wherein the MEMS device comprises the first electrode, a second electrode and a plate electrode movable from a first position disposed adjacent the first electrode and a second position disposed adjacent the second electrode;
discharging the voltage applied to the first electrode through a first resistor;
applying a voltage to the second electrode, wherein the voltage is applied to the second electrode either:
while discharging the voltage to the first electrode; or
after the capacitance of the first electrode has decreased;
increasing a capacitance of the second electrode; and
decreasing the capacitance of the first electrode, wherein the increasing and decreasing occurs while increasing the voltage applied to the second electrode.
15 . The method of claim 14 , wherein the plate electrode vibrates during the reducing, discharging, applying, increasing and decreasing.
16 . The method of claim 15 , wherein the vibrating decreases as the plate electrode moves from the first position to the second position.
17 . The method of claim 16 , wherein during the reducing the discharging, the voltage applied to the first electrode increases and wherein electrostatic force at the plate electrode increases while the voltage applied to the first electrode increases.
18 . The method of claim 14 , wherein during the reducing the discharging, the voltage applied to the first electrode increases.
19 . The method of claim 18 , wherein electrostatic force at the plate electrode increases while the voltage applied to the first electrode increases.
20 . The method of claim 14 , wherein applying the voltage to the second electrode occurs after the capacitance of the first electrode has discharged, and wherein the voltage applied to the first electrode increases.