Improvement Of Coupling Characteristics Of Sapphire Quasioptical Dielectric Resonator By Microstrip Line

摘要

Regularities of coupling of the leucosapphire quasioptical dielectric resonator (QDR) to the polytetrafluorethylene reinforced microstrip line (MSL) are experimentally investigated in the Ka-band. It is suggested to organize coupling in within the "QDR over MSL" space that is different from a known coupling "QDR on a MSL substrate". It is shown that at coupling with the help of the "QDR over MSL" the loss of the resonance field energy in a substrate is negligibly small as compared to the eigen losses in QDR. Presence of several coupling areas separated by zones of lack of coupling both for quasi-E and for quasi-H modes is revealed. Open resonators with metallic phase-correcting mirrors and sapphire dielectric resonators excited at higher azimuth modes of oscillations (whispering gallery mode waves) possess the highest value of the Q-factor in the millimeter band of radio waves under the room temperature. The latter resonators are usually called quasioptical dielectric resonators (QDR). In the devices where frequency control is not necessary, for example, at stabilization of the heterodyne frequency or in the filters, the preference is given to QDR due to their advantage in weight and dimension parameters. This advantage is especially evident in development of the modules using the microstrip design. The generally accepted method for the microstrip line (MSL) coupling with QDR is positioning of the resonator directly upon the dielectric substrate near the strip [1]. It is the same technique as that used at excitation of the dielectric resonators at lower modes [2,3]. It is quite apparent that using this method is related to inevitable losses δs for scattering of the accumulated in the resonator energy within the dielectric and on the metal screen of MSL because the field of eigen modes of QDR is concentrated not only inside the resonator but in the environment as well.