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Abstract

A body implantable medical apparatus includes circuitry for generating and transmitting a modulated analog data signal. A receiver receives and digitally demodulates the modulated analog signal. An analog-to-digital converting circuit produces an amplitude limited modulated digital signal corresponding to the modulated analog signal. The converting circuit includes an amplifier coupled to a receive antenna and a comparator having an input coupled to the amplifier and an output coupled to a digital demodulator. The digital demodulator demodulates the modulated digital signal to produce a digital information signal, such as a signal containing physiologic sensor data. The digital demodulator includes a digital delay line comprising a plurality of shift registers or, alternatively, a plurality of multiple-stage delay blocks each coupled to a tap selection device. The digital delay line includes an input coupled to an output of the converting circuit, an exclusive OR (XOR) gate having a first input coupled to an output of the digital delay line, and a conductor coupled between the input of the digital delay line and a second input of the XOR gate, such that delayed and non-delayed modulated digital signals are respectively applied to the first and second XOR gate inputs to produce a digital information signal at an output of the XOR gate. The digital demodulator may be implemented in a Field-Programmable Gate Array (FPGA), in an Application Specific Integrated Circuit (ASIC) or using a digital signal processor. A control circuit is coupled to the digital demodulator to adjust a rate at which the digital demodulator operates.

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First Claim