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Frequency locked-loop using a microcontroller as a comparator

  • US 5,705,955 A
  • Filed: 12/21/1995
  • Issued: 01/06/1998
  • Est. Priority Date: 12/21/1995
  • Status: Expired due to Term
First Claim
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1. A frequency-locked loop comprising:

  • a controllable oscillator for generating an output signal having a frequency the controllable oscillator having an input receiving a modulation signal in a transmission mode;

    a sampler, coupled to the controllable oscillator, for sampling the frequency of the output signal;

    a divider, coupled to the sampler, for dividing the frequency of the output signal to generate a prescaled signal;

    a microprocessor, coupled to the divider and the controllable oscillator, for performing a comparison of the prescaled signal to a reference signal and generating a non-continuous signal for correcting the frequency of the controllable oscillator output signal when not in the transmission mode, the microprocessor having instructions stored therein which control sampling by the sampler;

    a converter coupled to the microprocessor for converting the non-continuous control signal to an analog signal;

    a low pass filter coupled to the converter for filtering undesired components from the analog signal; and

    a summer coupled between the low pass filter and the controllable oscillator in order to provide for injection of the modulation signal.

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