Aliasing sampler for plasma probe detection

摘要

In a plasma arrangement in which an RF power generator produces an RF electrical wave at a predetermined RF frequency and containing harmonic information which affects the form of the RF wave, the electrical wave being supplied through an RF matching network to a power input of a plasma chamber within which the electrical wave produces a plasma. A detector samples the RF electrical wave at the input to the plasma chamber to determine a measurement of the RF electrical power applied to the plasma chamber. The detector includes a sampling device for sampling the amplitude of the RF wave at a predetermined sampling rate lower than the predetermined RF frequency, and device for synthesising the sampled amplitude to produce an aliasing waveform at a predetermined aliasing frequency significantly lower than the predetermined RF frequency, in which the aliasing waveform preserves the harmonic information of the RF wave.