Patent ID: 8330475

Claim:
Circuit for detecting a magnitude and a phase of an impedance of a load, the load being connectable to a radio frequency (RF) amplifier by means of a feed line, the circuit comprising: a) first means for sensing a peak value of an output voltage of the RF amplifier, the first means being connected by a node to the feed line; b) second means for sensing a peak value of an output current of the RF amplifier, the second means comprising a peak sensor element placed in the feed line and being circuited in series between the RF amplifier and the load, wherein the peak sensor element is a resistor, a capacitor or a coil; and c) third means for c1) measuring a signal whose value depends on the phase between output voltage and output current, or c2) deriving the phase between output voltage and output current using linear multiplication; d) whereby the first means and/or the second means for peak value sensing comprise, in a branch coupled to the feed line, d1) a mixer and an amplitude limiter or d2) a peak diode detector; e) wherein an energy flow from the RF amplifier to the load through the feed line is used for detecting the impedance and phase.