Patents by Inventor Fred T. J. Cheng

Fred T. J. Cheng 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: 4550424
    Abstract: An AM stereo receiver decoder is shown. An AM detector produces the stereo L+R signal and a PM detector produces the L-R signal. The PM detector is created from a conventional FM detector that employs an input limiter driving a balanced multiplier. The limiter also drives a tuned circuit which provides quadrature drive to the multiplier. An integrator connected to the FM detector converts the response to a PM decoder. A large value inductor is simulated to appear across the integrator so as to create a low modulation frequency resonance at a subaudible frequency thereby providing a controlled pilot tone response. The inductor is simulated by the action of a first G.sub.m amplifier driving a capacitor which drives a second G.sub.m amplifier having an output coupled back to the input of the first G.sub.m amplifier. The capacitor is switched by means of a series connected switch that disconnects the capacitor when the AM exceeds a predetermined value.
    Type: Grant
    Filed: February 9, 1984
    Date of Patent: October 29, 1985
    Assignee: National Semiconductor Corporation
    Inventors: Fred T. J. Cheng, Don R. Sauer