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of modes in the given frequency region the flat mirror of a conventional Fabri-Perot hemispherical open resonator have been replaced by a specially constructed mirror with a stepwise cross-section.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.
Open resonators with inhomogeneities
An analysis of electromagnetic properties of an Open Resonator (OR) with perfectly conducting cylindrical inhomogeneities is presented. The inhomogeneities of three types were studied. In the first case the conducting thin circular cylinder with a longitudinal slot is considered. This cavity-backed aperture possess the resonance features. It is shown that such cylindrical screen may be used in order to control the OR properties. The case of the conducting cylinders with rectangular and circular cross-section are considered too. It is shown that the inhomogeneity of small cross-sectional wave dimensions can both be imperceptible for the OR-field and efficiently scatter it, depending on location of the inhomogeneity in the OR. The theoretical analysis and experimental results are presented. The stationary wave model of the OR field is used in the theoretical analysis of scattering from cylindrical inhomogeneities. The generator of the cylindrical obstacles is parallel to the H vector of the incident field. The experiments were carried out in the millimeter wave band with the OR having spherical and flat mirrors. The numerical results are in a good agreement with the experimental data.
DESIGN CONSIDERATION TO PPM KLYSTRONS FOR INDUSTRIAL LINAC
Toshiba has been developing the C-band and X-band Periodic Permanent Magnet (PPM) focused klystron in collaboration with KEK and manufactured prototypes for the JLC project. [1] The PPM klystron has an advantage to enhance the total efficiency as a result of eliminating the electric power for the focusing magnet. From experience on the development the PPM focused klystrons for the JLC project, we plan to apply the PPM focused klystron to the medical and industrial linac. The periodic magnet focusing scheme has some technical difficulties such as stop band voltage. To design the PPM klystron for the medical and industrial linac, it is necessary to give heed to electron beam instability; so that the tube parameters of the PPM focused klystrons have some constraints. The size of the accelerator system is substantially reduced if a PPM focused klystron is used. The majority of medical and industrial linacs use frequencies of S-band range. We discuss the availability of the S-band PPM focused klystron in this paper.