LOW ENERGY CONSUMPTION RF TELEMETRY CONTROL FOR AN IMPLANTABLE MEDICAL DEVICE

摘要

A frequency synthesizer of an IMD functions in a PLL LOCK mode. The VCO frequency is governed by the PLL and an energy saving HOLD mode. The VCO generated carrier frequency can drift over time. The PLL is coupled with a control voltage of the VCO to develop a frequency control voltage during initial LOCK portions of telemetry transmission. The carrier frequency is modulated during uplink transmission of patient data. An AFC algorithm derives a frequency correction value from the difference in frequency of the constant received carrier frequency and the drifting VCO generated carrier frequency. A frequency correction value is applied to the VCO FM input. A recharge current is also applied to the capacitive loop filter.