Patent ID: 8643281

Claim:
A signal generating system comprising a signal generator for generating an electrical signal at a first frequency; an impedance matching circuit arranged to supply the electrical signal from the signal generator to a reactive load; and an impedance matching circuit control system for detecting the electrical signal between the signal generator and the reactive load and for adjusting the impedance matching circuit to achieve a predetermined condition, wherein the impedance matching circuit control system comprises; a heterodyne frequency generator coupled to the signal generator to generate a second, heterodyne frequency from the first frequency from the signal generator; a mixer, wherein the heterodyne frequency is mixed with the detected signal at the mixer to generate sum and difference signal; a filter for passing the difference signal; and a processor responsive to the difference signal to adjust the impedance matching circuit to achieve the predetermined condition; the signal generating system being characterized in that the detected electrical signal from the signal generator is fed to both the heterodyne frequency generator which generates said heterodyne frequency, and the mixer.