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Abstract

A software-controlled, external programmer for transcutaneously programming and receiving data from an implanted medical device providing enhanced discrimination and detection of pulse-interval-coded signals of interest telemetered out of the implanted medical device from undesirable transient and steady-state noise. The programmer incorporates a detector including an active mixer and a precision tuned active phase shifting network providing low level signal rectification, precise narrow bandpass filtering, and 30 decibels of amplification. At the detector, the received signal is mixed with a phase shifted version of itself to produce a detected DC component which is a function of frequency. The DC response emulates a system with a narrow 25 kHz bandpass filter operating at 175 kHz, but does not share its undesirable transient response. For signals in the reject band, the output produces a signal of the opposite polarity of the signals within the pass bands. Transient0 noise excites the receiver antenna and produces a ringing response accompanied by components above 400 kHz. The noise response of the antenna stimulates the detector to produce the intended inverted output. As the transient noise amplitude increases, the inverted response increases in amplitude driving the output level further away from the trigger level of a post-detection comparator. Similarly, any steady state noise signal in the reject band will also result in a steady state inverted response that does not trigger the comparator.

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