Analysis of an end launcher for a circular cylindrical waveguide

The self-reaction concept has been used to obtain a network representation of an end launcher exciting a dominant TE(11) mode circular waveguide from a coaxial line. There is good agreement between theoretical and experimental results on the input voltage standing wave ratio (VSWR) in the frequency range from 8.5 to 9.2 GHz. In this frequency range the minimum VSWR attained theoretically and experimentally is of the order of 1.2. The frequency at which the input reactance is zero and that at which the input resistance is 50 ohms are functions of the lengths of the longitudinal and radial arms of the loop. These two frequencies are found to be different. Further reduction in input VSWR is possible through an adjustment of the lengths of the longitudinal and radial arms of the loop.