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ANALYSING RF SIGNALS FROM A PLASMA SYSTEM

  • US 20150276833A1
  • Filed: 07/24/2013
  • Published: 10/01/2015
  • Est. Priority Date: 07/25/2012
  • Status: Abandoned Application
First Claim
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1. A method of analysing RF signals from a plasma system, comprising the steps of:

  • (a) receiving from the plasma system one or more signal channels, wherein the or each signal channel comprises a data source representing signals and noise from the plasma system across a frequency range;

    (b) identifying, in a first RF signal sample from one of said signal channel(s), a first frequency value, F, at which a local maximum is found in the frequency domain;

    (c) determining a first complex frequency-domain signal component at said first frequency value, F in said first signal sample;

    (d) identifying, in said first RF signal sample or in a further RF signal sample from one of said signal channel(s), a further frequency value F(N), where N is an integer representing an Nth order harmonic of said first frequency F, and wherein N=1 denotes a 1st order harmonic at the first frequency F;

    (e) determining a further complex frequency-domain component at said further frequency value in the RF signal sample in which said further frequency value is identified;

    (f) transforming the first complex frequency-domain component by adjusting its phase by an angle θ

    to a predetermined phase angle φ

    , to provide a phase-adjusted first complex signal component;

    (g) transforming the further complex frequency-domain component by adjusting its phase by an angle equal to N×

    θ

    , to provide a phase-adjusted further complex signal component;

    (h) iteratively repeating steps (b) to (g) in respect of a plurality of signal samples from the same plasma system, wherein in each iteration the value of θ

    is chosen to give a constant phase angle φ

    for the phase-adjusted first complex signal component across different iterations, and wherein within any iteration the value of θ

    chosen in step (f) is employed in the adjustment of step (g);

    (i) aggregating or averaging the phase adjusted first complex signal components obtained in each iteration;

    (j) aggregating or averaging the phase-adjusted further complex signal components obtained in each iteration.

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