Angular velocity sensor

An angular velocity sensor comprising:

• a frame having a hollow portion;
• a mass which is supported on the frame by way of resilient beams which are formed in the x-axis direction and the y-axis direction orthogonal to each other, has a thickness in the z-axis direction orthogonal to the x axis and the y axis respectively, wherein a surface portion of the mass functions as a movable electrode and changes a posture thereof corresponding to an external force;
• a plurality of fixed electrodes which is arranged to face the mass in an opposed manner;
• a first detection circuit which detects a change of electrostatic capacitance between the fixed electrode and the movable electrode along with the inclination of the mass in the y-axis direction;
• a second detection circuit which detects a change of electrostatic capacitance between the fixed electrode and the movable electrode along with the inclination of the mass in the x-axis direction;
• a third detection circuit which detects a change of electrostatic capacitance between the fixed electrode and the movable electrode along with displacement of the mass in the z-axis direction;
• a phase shifting means which shifts a phase of a carrier which is applied to the third detection circuit by 90° from a phase of a carrier wave which is applied to the first detection circuit and the second detection circuit;
• a switching means which alternately performs the application of carrier wave to the first detection circuit and the second detection circuit based on timing of a control clock signal by switching the application for every fixed cycle;
• an amplifying circuit to which output signals from the first detection circuit, the second detection circuit and the third detection circuit are inputted;
• a first separation means which separates an angular velocity component signal which is constituted of a first detection signal indicative of the change of the electrostatic capacitance in the first detection circuit and a second detection signal indicative of the change of the electrostatic capacitance in the second detection circuit and a third detection signal indicative of the change of the electrostatic capacitance in the third detection circuit from each other by performing phase division processing based on the timing of the control clock signal in response to the output signals from the amplifying circuit;
• a second separation means which separates the first detection signal and the second detection signals from each other by performing a time division processing based on switching timing of the carrier wave by the switching means in response to the angular velocity component signal;
• an angular velocity output means which outputs an angular velocity acting about the x axis of the mass in response to the first detection signal and outputs an angular velocity acting about the y axis of the mass in response to the second detection signal;
• and
• a driving means which oscillates the mass in the z-axis direction while performing a position control in response to the third detection signal.