Patent ID: 6940466

Claim:
A communication circuit to receive and transmit signals, comprising: an antenna element having a first terminal and a second terminal; at least one electrostatic conductor positioned to shield the antenna element from electric fields, wherein the antenna element is adapted to induce a received signal at the first and second terminals when the antenna element is in a magnetic field; a driver connected to at least one of the first and second terminals to energize the antenna element with a transmitted signal; a differential amplifier having a first input connected to the first terminal of the antenna element and a second input connected to the second terminal of the antenna element, the differential amplifier having a selectable input impedance, wherein a lower first input impedance is used to amplify the received signal from the antenna element, and a higher second input impedance is used to monitor the transmitted signal from the driver; and a switch to toggle an effective input impedance between the second impedance and the first impedance.