Diathermy unit
First Claim
1. A diathermy unit comprising oscillator means for generating an oscillatory radio frequency output signal, the oscillator means having at least one terminal for direct electrical connection to an electrical load in the form of living tissue and means for causing the radio frequency of said oscillatory output signal to vary automatically in response to the resistance of the living tissue load while the unit is in use.
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Accused Products
Abstract
A diathermy unit has a power oscillator with a resonant circuit arranged to be coupled to the load represented by the tissue to be treated. The resonant circuit includes a capacitor for connection in series with the load such that the resonant frequency varies with the load resistance. The resulting self-tuning of the oscillator allows improved matching of the oscillator to the load with consequent improved efficiency, a feature especially useful for a battery-powered unit. Regulation of the output power of the unit makes use of a feedback loop including an analogue multiplier for receiving signals representative of the power of the output stage, the resulting product signal being used to control pulse width modulation of the oscillator.
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20 Claims
- 1. A diathermy unit comprising oscillator means for generating an oscillatory radio frequency output signal, the oscillator means having at least one terminal for direct electrical connection to an electrical load in the form of living tissue and means for causing the radio frequency of said oscillatory output signal to vary automatically in response to the resistance of the living tissue load while the unit is in use.
Specification