The microstrip split-ring resonator (MSRR) microplasma source is analysed
and characterized using a microwave model of the device. Throughout the
discussion, experimental data for three MSRR designs are also presented.
The model identifies the key parameters that control the performance of the
device and results in the formulation of closed-form expressions useful for
designing, analysing and comparing MSRR designs. Matching the
microstrip characteristic impedance to the microplasma impedance is found
to be a key factor in the performance of these devices and it can be even
more critical than the quality factor of the ring resonator. Based on the
model, average rf electric fields of up to 4MVm−1 at 1Wof input power are
estimated to be generated in a 45μm gap device. Furthermore, the model is
used to determine the plasma impedance and thereby obtain information on
physical properties of the microdischarge. Electron densities of the order of
10(14) cm−3 are estimated in a 1W argon discharge at atmospheric pressure.
Based on the values of the plasma impedance, it is also determined that up to
70% of the power input to the MSRR is coupled to the electrons in the
microdischarge
