A microcontroller-based implantable telemetry system for sympathetic nerve activity and ECG measurement

A passive implantable telemetry system employing a low power 8 bit microcontroller has been designed for chronic unanesthetized small animal studies. The implantable renal nerve activity and ECG system is powered by induction coupling. The gains of the neural signal (NS) and ECG amplifiers are microprocessor-controlled by on-off-keying of transmitted power modulated at 144 bps. Analog signals from the NS and ECG amplifiers are each converted to an 8-bit serial digital format. This is accomplished by two 8-bit A/D converters included in the single microcontroller. The converted binary code is applied to a passive RLC serial resonant circuit and transmitted by electromagnetic wave.