  The microwave resonator is one of the key components in the modern Electron
Paramagnetic Resonance (EPR) spectroscopy setup, as it largely determines the
performance characteristics and limitations of the entire spectrometer. In this
research note the possible way of resonator optimization is described. A
detailed computer model describing the distribution of the electromagnetic
field for Bruker 4118X-MD-5W1 design resonator has been developed. All details
including a dielectric insert, conductive screen, coupling antenna and PTFE
supports were included in the model. All dissipation processes were considered
in the calculation. The influence of the resonator geometry on the Q-factor,
filling factor and operating frequency of the resonant mode has been
investigated. The resonator geometric parameters are optimized to achieve
maximum sensitivity. According to the calculations, the optimized resonator
structure has in 10 times greater sensitivity than the original MD-5 design.
