Efficient integrated RF telemetry transmitter for use with implantable device
First Claim
1. 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; and
a 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; and
an antenna coil coupled to the telemetry amplifier circuit which receives the amplified fixed frequency output signal.
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Accused Products
Abstract
An efficient RF telemetry transmitter system includes a first stage and a second stage. The transmitter system sends power and data to an implant device using pulse-width modulation of a high fixed frequency clock signal, e.g., a 49 MHz clock signal, within the first stage in order to provide efficient generation of an RF output signal in the second stage. Digital logic gates and related circuitry, e.g., implemented in an application specific integrated circuit (ASIC), are used in the first stage to provide pulse-width modulation of the fixed frequency clock signal in order to optimally set the drive level of the output signal of the first stage, or inter-stage signal. ON/OFF keying, or other modulation scheme, further modulates the clock signal with data in the first stage. The second stage includes a Class-E amplifier circuit implemented with a single RF transistor, biased with a temperature-compensated offset voltage set just below the cut-off voltage of the transistor. An LC filter placed in the front end of the second stage filters out all but the fundamental frequency component of the inter-stage signal. The drive level of the inter-stage signal is selected to prevent both overdriving and underdriving of the Class-E amplifier. An adjustable or selectable collector voltage coupled to the single RF transistor allows the amplitude of the output signal to be set to an optimum power level for transmission to the implant device.
278 Citations
20 Claims
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1. 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:
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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; and a 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, and an output amplifier circuit that efficiently amplifies the inter-stage drive signal to produce an amplified fixed frequency output signal; and an antenna coil coupled to the telemetry amplifier circuit which receives the amplified fixed frequency output signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A high frequency, highly-efficient, telemetry transmitter circuit for transmitting a modulated carrier signal to a remote receiver circuit, the telemetry transmitter circuit comprising:
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a fixed frequency oscillator that generates a fixed frequency clock signal; and a telemetry modulator circuit responsive to the fixed frequency clock signal and including means for pulse width modulating the fixed frequency clock signal in accordance with a selected first modulation signal, the pulse width modulated fixed frequency clock signal comprising the modulated carrier signal. - View Dependent Claims (19)
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20. A method for efficiently transmitting a modulated carrier signal to an implanted remote receiver, the method comprising:
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generating a fixed frequency clock signal having a frequency of F1 MHz, the clock signal comprising a train of pulses, each pulse having a pulse width, W, with the time interval between the leading edge of the adjacent pulses comprising a fixed time period T1 seconds, where T1=/F1; modulating the pulse width W of the first frequency clock signal in accordance with a selected first modulation signal to produce a pulse width modulated (PWM) inter-stage carrier signal, the first modulation signal defining the energy content, or drive level, of the PWM inter-stage carrier signal; modulating the PWM inter-stage carrier signal with data in accordance with a selected second modulation signal to produce a dual modulated inter-stage carrier signal, the second modulation signal representing data to be carried to the remote receiver via the modulated carrier signal; applying the dual modulated inter-stage carrier signal to a band pass filter circuit that rejects the higher harmonics of the fixed frequency clock signal, while passing the fundamental frequency of the fixed frequency clock signal, wherein the drive level of the passed fixed frequency clock signal varies as a function of the selected first modulation signal; efficiently amplifying the passed fixed frequency clock signal to produce an amplified fixed frequency output signal to produce an RF output signal having a frequency of F1 MHz, the RF output signal having data embedded therein that varies as a function of the second modulation signal; and transmitting the RF output signal to the remote receiver circuit through an antenna coil.
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Specification