  In this work, we study the development of a coplanar waveguide (CPW)
resonator and its use in an electron spin resonance (ESR) spectrometer. The CPW
resonator is designed to operate in S-band. It has a short circuit
configuration which leads to miniaturization. It is so constructed such that it
has a characteristic impedance of 50 ohms. Detailed electromagnetic simulation
with a particular emphasis on the excitation of the structure has been
performed for this resonator owing to its uniplanar nature. The design
parameters and the electromagnetic field distribution are obtained from the
simulation. The resonator is fabricated using optical lithography with a rapid
prototyping technique. The characteristic response of the resonator is measured
by coupling it to a Vector Network Analyzer (VNA). The ESR absorption spectrum
of free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) is captured by using this
resonator in reflection geometry. The microwave magnetic field distribution at
the sample position is investigated.The measured g-factor value is found to be
consistent with that reported in the literature. The quality factor of this
resonator is found to be low and this makes it suitable for use in a Pulsed ESR
spectrometer.
