Patents by Inventor Charles D. Hardwick

Charles D. Hardwick 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: 4087816
    Abstract: A low frequency radio position location system for aircraft or other vehicles for operating in conjunction with ground stations transmitting at a first VLF radio frequency which is shifted in frequency by a small amount to a second frequency at fixed intervals with the shifting being carried out coherently with a defined transition point at the frequency signal is made up of an RF receiver and amplifier, a phase-locked loop for providing a continuous output frequency signal precisely locked to the first frequency, a detector for deriving a signal at the modulation frequency, a phase comparator for comparing the phase relationship of the derived modulation frequency signal to the phase relationship of the output frequency signal and the second frequency signal. The derived modulation frequency signal and its phase information is then available for providing distance and position information in relation to the ground stations.
    Type: Grant
    Filed: October 22, 1976
    Date of Patent: May 2, 1978
    Assignee: Canadian Patents & Development Limited
    Inventors: Andrzej Barszczewski, Charles D. Hardwick