Importance

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Abstract

A bi-directional telemetry system includes an implanted unit that allows a high-speed transfer of digital data with minimal complexity of the electronic circuitry. A corresponding external unit is capable of decoding the high-data-rate transmitted information and, in turn, communicates with the implanted unit using pulse amplitude modulation. The data transmission rate of the implanted unit to the external device is 32 kbps, a four-fold increase over conventional data transmission rates, without increasing the carrier frequency. To this end, the implanted unit using a modified implementation of the quadrature amplitude modulation (QAM) method that generates the required symbols from readily available squarewave signals. Simulated sinewaves are generated within the transmitter by an inverting amplifier stage with variable input resistance determined by a pair of switches that are ultimately controlled by 16 k and 32 k clocks in the implanted unit. Data is encoded by changing the amplitude and polarity of the simulated sinewaves. Quadrupling of the data rate is achieved by taking advantage of the orthogonality of I and Q components, whose phases are in quadrature.

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First Claim