Resonance systems of millimeter wave oscillators

An analysis of open resonators specially designed for millimeter wave sources which are characterized by high frequency stability is presented. The obtained numerical results and experimental data have been used to improve the characteristics of oscillating systems formed by a two-mirror resonator with metal rod inside. To proceed the preselection of modes in the given frequency region the flat mirror of a conventional Fabri-Perot hemispherical open resonator have been replaced by a specially constructed mirror with a stepwise cross-section. The further tune axial mode filtration and the complete transverse modes suppression have been achieved by the insertion of a metal rectangular rod into the resonant cavity. The determining of parameters of the stepwise mirror and the rod is based on a detail theoretical investigation of the problem of wave scattering from these structures. Experimental results are in good agreement with numerical data. The designed open resonators can be used for generation of electromagnetic waves in the frequency region from 30 to 150 GHz. 1. The analysis of electromagnetic fields in open quasi-optical resonators has been extensively investigated because of its importance for solid-state sources design and for measurement problems in the millimeter wave band (Kotserzhinsky et al (1)). An introduction of GaAs and InP active elements into high Q circuits led to the development of millimeter wave oscillators characterized by rather high output power (about 100 mWt) and by a high frequency stability. The quality of a signal depends on the Q-factor of a circuit used in oscillators.