Optimum Design of Stepped Transmission-Line Transformers

This paper describes the optimum stepped-transmission-line transformer structure for matching two unequal characteristic impedances. For any specified bandwidth, the steps are designed to yield a Tchebycheff-type (or equal-ripple) reflection-coefficient response. Over this band, the maximum vswr is less than that obtainable with any other stepped-transformer having the same number of steps. Design method and technique for eliminating discontinuity-capacitance effects are given. The measured results for a coaxial and a waveguide model are presented and found to verify the method.