Patent ID: 6073050
Filing Date: 2000-06-06
Classification: A61N

Abstract:
A cochlear implant system comprising an external part and an implant part, the implant part having an implantable receiver circuit and implantable means for generating and applying a stimulation current to a selected pair of implantable electrodes, the external part having an RF telemetry transmitter for transmitting power and data to the implant part, the RF telemetry transmitter comprising:a fixed frequency oscillator that generates a fixed frequency clock signal;a telemetry modulator circuit responsive to the fixed frequency clock signal and including a pulse width modulator for modulating the pulse width of the fixed frequency clock signal in accordance with a selected first modulation signal to produce an inter-stage drive signal; anda telemetry amplifier circuit responsive to the inter-stage drive signal that efficiently produces an RF output signal at the fixed frequency of the clock signal for transmitting to the implantable receiver circuit of the implant part; the telemetry amplifier circuit comprising:a band pass filter circuit that rejects the higher harmonics of the inter-stage drive signal, while passing the fundamental frequency of the fixed frequency clock signal, thereby causing a drive level of the passed fixed frequency clock signal to vary as a function of the selected first modulation signal, andan output amplifier circuit that efficiently amplifies the inter-stage drive signal to produce an amplified fixed frequency output signal; andan antenna coil coupled to the telemetry amplifier circuit which receives the amplified fixed frequency output signal.