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RF MEASUREMENT AND
CONTROL
1. Background Information:
4. PSoC Microcontroller:
A plasma is an electrically conductive gas containing
charged particles. When atoms of a gas are excited to
high energy levels, the atoms loose hold of some of their
electrons and become ionized producing a plasma
containing electrically charged particles - ions and
electrons. Below is a Paschen curve that shows the
breakdown voltages for various gasses.
PSoC Designer with GUI
Pre-configured user modules
USB 2.0 integrated
Cheap and widely used
2. Applications:
Luke Nemuras
Richard Ooi
7. Plasmas in Action:
5. Circuit Schematic:
Surgical applications
Surface decontamination
Water purification
Plasma medicine
Fig 2: RF Control Circuit with Dynamic Feedback
Fig 1: Paschen Diagram
3. Project Goals:
Create a matching circuit to dynamically control RF
plasma utilizing a feedback loop to control frequency
of a resistive/ inductive load.
- Operate on the minimum of the Paschen Curve by
maintaining resonance at the load. Thermal
considerations and external field interruptions cause
us to operate elsewhere on the curves. This causes
loss and unnecessary heat.
Reduce the size of the circuit to achieve benefits of
a portable device.
Frequency of operation: 13.56 MHz +/- 500kHz
VCO: TI4046 @ 600 Hz per mV resolution
Pre-amp: AD8001 low power amplifier
Amplifier: Sirenza 18 dB amplifier
LC Load: L: 12.5uH C: 22pF Q: 720
∆Phase: AD8302
PSoC: A to D and D to A converter.
External supplies: +/- 5Vdc, 28Vdc
6. Dynamic Feedback
By monitoring the phase between the voltage and
current at the load we can decipher where we are
operating relative to to the resonance frequency. This
is done suing a combination of the AD8302 and PSoC.
By adjusting our frequency into resonance we can
minimize watts and heat while maintaining plasma
ignition
Acknowledgments:
Thanks to the following companies for donating
materials to our project: Analog Devices, AVX,
RFMD(Sirenza), Texas Instruments, Covidien, SiTime
and Advanced Energy.
Thanks to Dr. Collins, Dr. Moore, Dr. Grinolds, Doug
Scott, Brian Campbell, Mike Kabala, Ashish Sharma
and Olivera Notaros for their advice and technical
guidance for this project.