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Continuous time correlator architecture

  • US 9,625,507 B2
  • Filed: 02/04/2014
  • Issued: 04/18/2017
  • Est. Priority Date: 02/25/2011
  • Status: Active Grant
First Claim
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1. A system comprising:

  • a signal generator that outputs an excitation signal having a first frequency “

    f”

    ;

    an amplifier; and

    a correlator, the correlator including a mixer and an integrator, that rejects noise by performing synchronous demodulation wherein;

    a first end of a capacitance to be measured receives a first signal, the first signal being the excitation signal multiplied by a reference voltage;

    the mixer is connected to an output of the signal generator that outputs the excitation signal and to an output of the amplifier, an input of the amplifier being connected to a second end of the capacitance to be measured,the mixer receives the excitation signal from the output of the signal generator and receives a second signal from the output of the amplifier and multiplies the received excitation signal and the received second signal and produces an output, the output including a first DC voltage plus a sine term having a second frequency approximately 2f;

    the integrator filters out noise by providing a band-pass filtering function with a peak around f, integrates the output of the mixer and generates an output signal based on a correlation between the excitation signal and the second signal; and

    the output signal is a second DC voltage that is proportional to a capacitance value of the capacitance.

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