Patent ID: 8471568

Claim:
A circuit for evaluating a charge impedance at the output of a directional coupler having a first line adapted to convey a desired signal between a first terminal and a second terminal adapted to be connected to an antenna, and having a second line coupled to the first line, the second line comprising a third terminal on the side of the first terminal and a fourth terminal on the side of the second terminal, the circuit comprising: a first input terminal adapted to be connected to said third terminal of the coupler; a second input terminal adapted to be connected to the fourth terminal of the coupler; a homodyne detector having a first input for a signal to be processed connected to said second input terminal and having a second local oscillator input connected to said first input terminal, wherein the homodyne detector derives its local oscillator input from the third terminal of the directional coupler; a first low-pass filter having an input connected to a first output of the homodyne detector and providing first data relative to the charge impedance; and a second low-pass filter having an input connected to a second output of the homodyne detector and providing second data relative to the charge impedance.