Comparative TE modal analysis and extended parameter calculations of magnetron-wall waveguide for gyro-peniotron applications

Accurate determination of the magnetron-wall waveguide modal content is approached by examining the waveguide transverse cutoff constant (for which no closed-form analytic solution is known). The method of solution involves dividing the waveguide into two regions, an inner (circular) region and an outer (slot) region, assuming a constant electric field at the common interface, and equating the impedance functions at the interface. Computer calculations include large ratios of outer-to-inner wall radii (20:1), normalized slot angles between 0.01 and 0.99, a variable number of vanes (2-30), and higher-order modes that have not been previously reported. Mode numbering of the higher-order modes is also considered. The TE mode spectrum is plotted as a function of waveguide geometry. A waveguide model was built, and frequency resonances were measured. Resonances were correlated using a scanning filter computer program and used to calculate the modal cutoff frequencies. Experimental data agree with calculated values to within 1.25, 0.57, 0.49, and 2.48% for the four modes detected thus far. Results for lowest-order modes agree with those of other investigators to within about 5% or better in most instances.< >