Impedance matching of an electromagnetic transponder reader
First Claim
1. A terminal for generating an electromagnetic field, comprising an oscillating circuit capable of receiving a high-frequency A.C. excitation voltage via an amplifier and a directional coupler, wherein the oscillating circuit comprises at least one element of variable capacitance, and said terminal comprises, for modifying the value of said capacitance according to the amplitude of a signal extracted from the coupler, a comparator comparing the voltage extracted from the coupled line of the coupler with a reference voltage selected to maintain the impedance of the oscillating circuit at a predetermined value.
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Accused Products
Abstract
A terminal for generating an electromagnetic field, including an oscillating circuit capable of receiving a high-frequency A.C. excitation voltage via an amplifier and a directional coupler, the oscillating circuit having at least one element of variable capacitance, and circuitry for modifying the value of this capacitance according to the amplitude of a signal extracted from the coupler.
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Citations
4 Claims
- 1. A terminal for generating an electromagnetic field, comprising an oscillating circuit capable of receiving a high-frequency A.C. excitation voltage via an amplifier and a directional coupler, wherein the oscillating circuit comprises at least one element of variable capacitance, and said terminal comprises, for modifying the value of said capacitance according to the amplitude of a signal extracted from the coupler, a comparator comparing the voltage extracted from the coupled line of the coupler with a reference voltage selected to maintain the impedance of the oscillating circuit at a predetermined value.
Specification