Antenna resonant circuit
First Claim
1. A parallel antenna resonant circuit, operable to transmit and receive, and having a selected transmit resonant frequency and a selected receive resonant frequency, comprising:
- an antenna coil for transmitting and receiving HF signals, said antenna coil also operable as a first resonant frequency-determining element;
a second resonant frequency-determining element connected in parallel with said first resonant frequency-determining element;
a series combination of a third resonant frequency-determining element and a threshold value switch, said series combination in parallel with said first and second resonant frequency-determining elements, said threshold value switch operable to be electrically conductive in response to said transmitted HF signal, during a transmit mode, thereby determining the selected transmit resonant frequency to be a function of the parallel combination of said first, second and third resonant frequency-determining elements and said threshold value switch operable to present a high resistance to said received HF signal during a receive mode thereby effectively eliminating the effect of said third resonant frequency-determining element from said resonant circuit, and determining the selected receive resonant frequency to be a function of the parallel combination of said first and said second resonant frequency-determining elements.
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Accused Products
Abstract
An antenna resonant circuit (10) is described having a coil (18, 26) and a capacitor (30) as frequency-determining elements for use in a transmitting/receiving device which in a transmitting operating phase transmits HF signals of high power and in a receiving operating phase receives HF signals of low power. In the antenna resonant circuit (10) parallel to the capacitor (30) there is a series circuit of a further capacitor (32) and a threshold value switch (34, 36). Said threshold value switch (34, 36) is of high resistance when the voltage applied thereto is smaller than its threshold value and of low resistance when the voltage applied thereto is greater than its threshold value. The threshold value of the threshold value switch (34, 36) is so set that it is greater than the voltage applied thereto in the receiving operating phase but smaller than the voltage applied thereto in the transmitting operating phase.
27 Citations
6 Claims
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1. A parallel antenna resonant circuit, operable to transmit and receive, and having a selected transmit resonant frequency and a selected receive resonant frequency, comprising:
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an antenna coil for transmitting and receiving HF signals, said antenna coil also operable as a first resonant frequency-determining element; a second resonant frequency-determining element connected in parallel with said first resonant frequency-determining element; a series combination of a third resonant frequency-determining element and a threshold value switch, said series combination in parallel with said first and second resonant frequency-determining elements, said threshold value switch operable to be electrically conductive in response to said transmitted HF signal, during a transmit mode, thereby determining the selected transmit resonant frequency to be a function of the parallel combination of said first, second and third resonant frequency-determining elements and said threshold value switch operable to present a high resistance to said received HF signal during a receive mode thereby effectively eliminating the effect of said third resonant frequency-determining element from said resonant circuit, and determining the selected receive resonant frequency to be a function of the parallel combination of said first and said second resonant frequency-determining elements. - View Dependent Claims (2, 3, 4, 5, 6)
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Specification