Angular rate sensor with quadrature error compensation
An angular rate sensor ( 20 ) includes a drive mass ( 36 ) flexibly coupled to a substrate ( 22 ). A sense mass ( 42 ) is suspended above the substrate ( 22 ) is and flexibly connected to the drive mass ( 36 ) via flexible support elements ( 44 ). A quadrature compensation electrode ( 24 ) is associated with the drive mass ( 36 ) and a sense electrode ( 28 ) is associated with the sense mass ( 42 ). The drive mass ( 36 ) and the sense mass ( 42 ) oscillate together relative to a sense axis ( 50 ) in response to quadrature error. The quadrature error produces a signal error component ( 78 ) between the quadrature compensation electrode ( 24 ) and the drive mass ( 36 ) and a signal error component ( 76 ) between the sense electrode ( 28 ) and the sense mass ( 42 ). The compensation and sense electrodes ( 24, 28 ) are coupled in reverse polarity so that the signal error component ( 78 ) substantially cancels the signal error component ( 76 ).
1. An angular rate sensor comprising:
a substrate;
a drive mass flexibly coupled to said substrate, said drive mass including first and second regions separated by an axis of rotation oriented parallel to a surface of said substrate;
a sense mass suspended above said substrate and flexibly connected to said drive mass via flexible support elements, said sense mass including third and fourth regions separated by said axis of rotation, said first and third regions being laterally disposed on a first side of said axis of rotation, and said second and fourth regions being laterally disposed on a second side of said axis of rotation;
a first electrode associated with said drive mass and disposed beneath said first region; and
a second electrode associated with said sense mass and disposed beneath said fourth region, said second electrode being electrically coupled to said first electrode in reverse polarity so that a first error component between said first electrode and said drive mass substantially cancels a second error component between said second electrode and said sense mass.
2. An angular rate sensor as claimed in claim 1 wherein:
said drive mass together with said sense mass is configured to move with an oscillatory motion relative to a drive axis;
said flexible support elements enable said sense mass to oscillate relative to a sense axis that is perpendicular to said drive axis in response to an angular velocity about an input axis that is perpendicular to each of said drive and said sense axes; and
said drive mass together with said sense mass oscillates relative to said sense axis in response to a quadrature error, said quadrature error producing said first error component at said first electrode and said second error component at said second electrode.
3. An angular rate sensor as claimed in claim 1 wherein:
said first electrode is a quadrature compensation electrode; and
said second electrode is a sense electrode.
4. An angular rate sensor as claimed in claim 1 further comprising a positive output terminal electrically coupled with said second electrode, wherein said second electrode is a positive pole of said angular rate sensor and said first electrode is a negative pole of said angular rate sensor.
5. An angular rate sensor as claimed in claim 4 further comprising:
a third electrode associated with said drive mass;
a fourth electrode associated with said sense mass, said fourth electrode being electrically coupled to said third electrode; and
a negative output terminal electrically coupled with said fourth electrode, wherein said fourth electrode is a negative pole of said angular rate sensor and said third electrode is a positive pole of said angular rate sensor so that a third error component between said drive mass and said third electrode substantially cancels a fourth error component between said sense mass and said fourth electrode.
6. An angular rate sensor as claimed in claim 1 wherein:
said first electrode is fixedly attached to said first region of said drive mass or to said substrate underlying said first region; and
said second electrode is fixedly attached to said fourth region of said sense mass or to said substrate underlying said sense mass.
7. An angular rate sensor as claimed in claim 1 further comprising:
a third electrode associated with said drive mass and disposed beneath said second region; and
a fourth electrode associated with said sense mass and disposed beneath said third region, said third electrode being coupled to said fourth electrode so that a third error component between said drive mass and said third electrode substantially cancels a fourth error component between said sense mass and said fourth electrode.
8. An angular rate sensor as claimed in claim 1 wherein said axis of rotation is a sense axis, and said drive mass together with said sense mass is configured to move with said oscillatory motion about a drive axis that is perpendicular to said surface, and said flexible support elements enable said sense mass to oscillate about said sense axis in response to an angular velocity about an input axis that is perpendicular to each of said sense and drive axes.