THE HIGHER ORDER MODES IN THE OPEN RESONATOR WITH THE SEGMENT OF THE CIRCULAR WAVEGUIDE

Purpose: Study of the TE01 wave excitation efficiency in a segment of the circular waveguide located in the center of one of the mirrors of the open resonator with the help of the higher order mode TEM30q (in the Hermite-Gauss functions) and the degenerate mode TEM*11q. Design/methodology/approach: To determine the TE01 wave excitation efficiency in a segment of a circular waveguide using the higher resonator oscillations, an aperture area ratio of the mirror antennas is used. Loaded Q-factors of a hemispherical open resonator and a resonator with a circular waveguide segment are determined by the width of the resonance curve at the level of –3 dB. Findings: It has been established that the TE01 wave maximum excitation efficiency in a circular waveguide when using the TEM30q mode is 0.121 with the circular waveguide radius relative value being 0.993, and using the TEM*11q mode it is 0.242 for the same radius value. When the considered wave was excited by using only the central part of the TEM*11q, which field amplitude distribution on the open resonator mirror corresponds to the two rings, then the TE01 wave maximum excitation efficiency grew up to 0.954. Experimental studies were made in the two-millimeter wavelength range. The results of the made measurements showed that due to the circular waveguide segment the TEM30q mode transformed into the TEM*11q mode which stably exists in the resonator during its tuning. In this case, the presence of a circular waveguide segment does no result in the decrease of the loaded Q-factor of the resonance system. Conclusions: The here proposed quasi-optical resonant system can be used as a highly efficient power combiner in the subterahertz frequency range.