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Method and apparatus for synchronous demodulation of multiply modulated signals

  • US 6,714,025 B2
  • Filed: 02/19/2002
  • Issued: 03/30/2004
  • Est. Priority Date: 02/17/2001
  • Status: Active Grant
First Claim
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1. A method to synchronously demodulate a multiply modulated rotation rate signal of a rotation rate sensor having a spring-mass system that oscillates at its natural resonant frequency and at least one capacitor to ascertain a rotation rate of a Coriolis effect acting on the spring-mass system, the method comprising:

  • generating a time-variable first electrical signal so that it exhibits a time-invariant phase relationship to the natural resonant frequency of the rotation rate sensor;

    superimposing a second electrical signal, at the natural resonant frequency of the rotation rate sensor, on the first electrical signal to provide a multiply modulated electrical signal, an amplitude of the second electrical signal of a time-variable capacitance change of the at least one capacitor being correspondingly modulated; and

    ascertaining the time-variable capacitance change associated with the rotation rate and ascertaining the rotation rate by multiply demodulating a multiply modulated electric signal;

    wherein;

    the at least one capacitor includes two stationary capacitor electrodes and a capacitor electrode that is movable as a consequence of the action of the rotation rate;

    the capacitor electrode is movable toward a first one of the two stationary capacitor electrodes and simultaneously movable away from a second one of the two stationary capacitor electrodes, the moving of the capacitor electrode bringing about two time-variable and mutually inverse capacitance changes;

    the second electrical signal superimposed on the first electrical signal is modulated in accordance with the two time-variable and mutually inverse capacitance changes; and

    the multiply modulated electrical signal is conveyed to a capacitance/voltage converter that delivers two mutually inverse time-variable voltage signals;

    wherein in a first step, a first mutually inverse time-variable voltage signal is conveyed to a first input of a summer under a control of a first control signal, and a second mutually inverse time-variable voltage signal is conveyed to a second input of the summer under the control of the first control signal.

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