Patents by Inventor Thomas D. Stephen

Thomas D. Stephen has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 5057793
    Abstract: A frequency synthesizer phase locked loop includes a voltage controlled oscillator (VCO) providing a variable frequency signal, a reference frequency oscillator providing a reference frequency signal, a phase comparison circuit for comparing the phases of the variable frequency and reference frequency signals and providing an output signal to a loop filter, the output of the loop filter providing a frequency control signal to the VCO. The phase comparison circuit includes a digital phase detector providing an output signal on an output line coupled to a charge pump for providing a first output signal to the loop filter; and an analog phase detector including a sample and hold circuit, and a control circuit responsive to the variable and reference frequency signals for providing a signal for sampling to the sample and hold circuit, the sample and hold circuit providing a second output signal to the loop filter.
    Type: Grant
    Filed: October 29, 1990
    Date of Patent: October 15, 1991
    Inventors: Nicholas P. Cowley, Thomas D. Stephen