Radiofrequency Emission or Reception Chain with Automatic Impedance Adaptation, and Corresponding Method

A radiofrequency transmit or receive chain working at a nominal frequency F0, comprising:

• at least one amplifier, an antenna, an impedance matching network disposed between the amplifier and the antenna and comprising adjustable impedances, a measurement impedance of known complex value inserted in series between the amplifier and the matching network,
• means of measurement of the potentials present at the terminals of the measurement impedance for determining at one and the same time the current in the measurement impedance and a voltage at the output of the amplifier for a transmit chain or a voltage at the input of the amplifier for a receive chain,
• means of calculation
• of the complex impedance defined by the ratio of the voltage and the current, this complex impedance representing an existing load impedance or input impedance of the amplifier,
• of an impedance of the antenna,
• and of new values of the adjustable impedances of the matching network which make it possible to obtain a desired load impedance or input impedance for the amplifier,
• and
• means of electrical control of the matching network for adjusting the adjustable impedances to these new values,
• wherein the chain comprises a measurement frequency generator linked to the output of the transmit amplifier or to the input of the transmit amplifier, so as to inject thereinto a measurement frequency Fm different from the working frequency F0, the calculation means being designed to make impedance calculations on the basis of voltages and currents measured at the frequency Fm, and thereafter applying a correction so as to bring the calculated impedances to the values that they would have for the frequency F0.