Patent ID: 8140033

Claim:
Automatic impedance matching method for a radiofrequency transmission system comprising an amplifier, an antenna, and an impedance matching network between the amplifier and the antenna, the impedance matching network comprising several impedances, some of which have adjustable numerical values, and the radiofrequency transmission system having optimal desired performances when a nominal load impedance is connected at an output of the amplifier, the method comprising the steps of: measuring current and voltage at the output of the amplifier; calculating a complex impedance defined by the ratio between the voltage and the current, taking account of phase shift between the current and the voltage, the calculated complex impedance representing a present load impedance of the amplifier; calculating an antenna impedance as a function of the present load impedance and as a function of the known present values of the adjustable impedances of the impedance matching network; calculating, from the calculated antenna impedance, new values for the adjustable impedances of the impedance matching network that allow an overall load impedance of the amplifier to be obtained which is as close as possible to the nominal load impedance; and controlling the impedance matching network to adjust the adjustable impedances to the calculated new values.