||The highest achievable quality factor
(Q) values of a microwave resonator may be restricted by radiation
losses caused by intermode coupling. It may be difficult to improve Q
by dumping the intermode coupling while a complete mode spectrum is
unknown. This is a true for semi-open microstrip-like resonators.
Previously it has been found that negligible geometry fluctuations of
the microstrip resonators result in strong and unpredictable changes of
Q from less than 10E3 to higher than 10E5. Here we have studied the
influence of the dispersion properties on the loss characteristics of
the superconducting microstrip-like resonator. Transmittance spectra of
the half-wave resonator have been measured in 10 GHz frequencies range.
The electromagnetic field was intentionally disturbed outside in the
region of transmission lines to dump modes selectively. Series of Q
measurements using short-circuited stubs on input and output microstrip
lines were performed in order to find interaction of the main half-wave
resonance mode with other modes. It is found that spectrum of
resonances includes parasitic modes, the energy of which is
concentrated mainly in the region of connecting microstrip lines.
Interaction of the main mode with parasitic ones significantly reduces
the highest Q value of the main operating mode. It is also demonstrated
that dielectric resonance in the dielectric substrates of resonator can