Pulse to sinewave telemetry system

摘要

A telemetry system for communicating with a tank circuit contained in a pacer implanted in a patient includes a telemetry coil and a capacitor connected to the telemetry coil for forming a resonant tank. The telemetry coil is positionable externally on the patient's skin substantially overlying the implanted pacer. The resonant tank has a varying impedance in response to telemetered digital data signals from the implanted tank circuit. A clock oscillator generates a squarewave at a selected frequency. A delayed clock-to-pulse converter is responsive to the squarewave for generating drive pulses which are slightly delayed from the leading edges of the squarewave. A coil driver generates a sinusoidal carrier waveform having a varying amplitude and frequency in response to the drive pulses and to the varying impedance of the resonant tank. A sample and hold circuit is provided for sampling each cycle of the sinusoidal carrier waveform of the varying amplitude and frequency to provide a sample and hold signal. An output circuit is coupled to the sample and hold circuit for recovering of the telemetered digital data signal in the form of a binary pulse-width modulated signal.