Derivation of an equivalent circuit of Kurokawa-type oscillator resonance structure using an electromagnetic simulator

A resonance structure of a cross-coupled coaxial-line-TM/sub 010/ mode cylindrical cavity together with a rectangular waveguide coupled with the cavity via a cavity-waveguide coupling slot and with a built-in band-reject filter (a choke and an absorber)-is analysed by means of an electromagnetic simulator. The analysis is separately carried out for two distinct parts of the structure: (a) a cross-coupled coaxial-line-cavity-waveguide three-port and (b) a choke-absorber one-port. Equivalent circuits, whose parameters are derived in an optimisation process, in which the circuit modelled S-parameters are fitted to those calculated by the electromagnetic solver, are proposed. As a result of such an analysis and optimisation, we obtain the frequency dependent characteristics of the whole two-port passive structure used in a single-cavity single Gunn-diode oscillator.