MEMS resonators
A MEMS piezoresistive resonator ( 8, 78 ) is driven at a higher order eigenmode ( 32 ) than the fundamental eigenmode ( 31 ). The route of flow of a sense current ( 22 ) is arranged in relation to a characteristic of the higher order eigenmode ( 32 ), for example by being at a point of maximum displacement ( 50 ) or at a point of maximum rate of change with respect to distance (x) of displacement of the higher order eigenmode ( 32 ). The route of flow of the sense current ( 22 ) may be arranged by fabricating the MEMS piezoresistive resonator ( 8, 78 ) with a trench ( 15 ) formed between two beams ( 11, 12 ) of the MEMS piezoresistive resonator ( 8, 78 ), the end of the trench being located at the above mentioned position.
1. A method of operating a MEMS piezoresistive resonator;
the method comprising driving the MEMS piezoresistive resonator at a higher order eigenmode than the fundamental eigenmode.
2. A method according to claim 1 , further comprising arranging a route of flow of a sense current in relation to a characteristic of the higher order eigenmode.
3. A method according to claim 2 , wherein the route of flow of the sense current is arranged in relation to the characteristic of the higher order eigenmode by being at a point of maximum displacement of the higher order eigenmode.
4. A method according to claim 2 , wherein the route of flow of the sense current is arranged in relation to the characteristic of the higher order eigenmode by being at a point of maximum rate of change with respect to distance of displacement of the higher order eigenmode.
5. A method according to claim 2 , wherein the route of flow of the sense current is arranged by locating the end point of a trench of the MEMS piezoresistive resonator at a position determined in relation to the characteristic of the higher order eigenmode, the trench being formed between two beams of the MEMS piezoresistive resonator.
6. A MEMS piezoresistive resonator comprising a trench formed between two beams, the end of the trench located at a position of maximum displacement or maximum rate of change with respect to distance of displacement of a higher order eigenmode of the MEMS piezoresistive resonator.
7. A MEMS piezoresistive resonator according to claim 6 , wherein the MEMS piezoresistive resonator further comprises a head that is wider than the width of the overall footprint of the two beams, and wherein the end of the trench is located at a point along the beams that is before where the beams reach the head.
8. A MEMS piezoresistive resonator system;
the system comprising:
a MEMS piezoresistive resonator; and
a driver for the MEMS piezoresistive resonator arranged to drive the MEMS piezoresistive resonator at a frequency of a higher order eigenmode than the fundamental eigenmode of the MEMS.