| 摘要 |
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.
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