Patents Represented by Law Firm Frelich, Hornbaker, Wasserman, Rosen & Fernandez
  • Patent number: 4220156
    Abstract: An implantable AM receiver having a variable threshold which can detect signals above a changing noise level. An AM receiver is provided which provides a modulation envelope corresponding to the amplitude of a pulse-modulated RF signal radiated by an external device. A voltage signal is developed which is at least equal to the amplitude of the modulation envelope, but which decays at a predetermined rate if the modulation envelope drops to a value below the voltage signal. The voltage signal is then scaled to a predetermined percentage of a value corresponding to the value of the modulation envelope, and biased so that it cannot drop below a predetermined minimum level. The scaled voltage signal comprises the variable threshold and is compared by a comparator to the modulation envelope. If it is below the modulation envelope, the comparator outputs a voltage having a first state; if it is above the modulation envelope, the comparator outputs a voltage having a second state.
    Type: Grant
    Filed: November 3, 1978
    Date of Patent: September 2, 1980
    Assignee: Pacesetter Systems, Inc.
    Inventors: Joseph H. Schulman, Wayne A. Morgan