Baseband RF voltage-current probe
USRE38273E1 · kind E1 · reissue
Assignee
Inventors
Key dates
| Filing date | Jun 22, 2000 |
| Grant date | Oct 14, 2003 |
| Priority date | — |
| Expiry date | Jun 22, 2020 |
Classification
- Technology area (CPC —)General
Abstract
An RF probe for a plasma chamber picks up current and voltage samples of the RF power applied to an RF plasma chamber, and the RF voltage and current waveforms are supplied to respective mixers. A local oscillator supplies both mixers with a local oscillator signal at the RF frequency plus or minus about 15 KHz, so that the mixers provide respective voltage and current baseband signals that are frequency shifted down to the audio range. The phase relation to the applied current and voltage is preserved in the baseband signals. These baseband signals are then applied to a stereo, two-channel A/D converter, which provides a serial digital signal to a digital signal processor or DSP. A local oscillator interface brings a feedback signal from the DSP to the local oscillator. The DSP can be suitably programmed to obtain complex Fast Fourier Transforms of the voltage and current baseband samples. The frequency-domain spectra are analyzed to obtain, with great accuracy, magnitude of voltage and current and phase angle. Other parameters are derived from these three.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.