Spectrum of OR Oscillations with Aperture Excitation Method

The paper analyzes the oscillation spectrum of a hemispherical open resonator (OR). The first highest axially asymmetric type of TEM
10q
oscillations is excited in the resonator with the help of two aperture coupling elements located symmetrically with respect to the resonator axis. Each coupling element is a pyramidal horn with an aperture of 6.9×9.6 mm and a length of 85 mm. The connection of the input waveguides with a cross section of 3.6 × 1.8 mm with the resonator is controlled using one-dimensional E-polarized diffraction gratings, which are located on the surface of a flat mirror. A grating with a period of 0.6 mm and a lamella thickness of 0.02 mm was used in the experiment. It is shown that the excitation efficiency of the TEM
10q
mode in a hemispherical OR using two aperture coupling elements is 0.816. The oscillation spectra of the same resonator excited by slot and aperture coupling elements are compared. It has been established that with the aperture method of excitation, a significant rarefaction of the oscillation spectrum of the resonator occurs.