Slow wave transmission line transformers

Abstract

Development of a periodic structure to coupled slow- and fast-wave transmission lines is described. The slow-wave line is a coaxial line with rectangular corrugations on the outer conductor and with smooth metallic walls for the inner conductor. The fast-wave structure is a coaxial line with smooth inner and outer metallic conductors, or with outer conductors where the corrugation depth approaches zero. The unit cells, or quarter-wave sections, are developed for both binomial and Chebyshev coefficients. The Chebyshev transformer is designed for arbitrary bandwidths from 1.0 to larger numbers, and when the bandwidth equals 1.0, the binomial and Chebyshev transformers are identical. The Chebyshev coefficients are applied in calculating characteristic impedances for prescribed input and output line impedances. The modification here is inclusion of slow/fast wave velocities to the characteristic impedance. >