Characteristics of a Broadband Microwave Corrugated Feed: A Comparison Between Theory and Experiment

Abstract

A corrugated feed with nearly ideal radiation characteristics from 17 GHz to 29 GHz has been built using a novel fabrication technique. The bandwidth of single-mode operation was maximized by properly choosing the input parameters of the feed. As a result, only the fundamental mode can propagate at the input from 19 GHz to 28.8 GHz. In this frequency range, the far field is essentially polarized in one direction. At frequencies higher than 28.8 GHz, there is a cross-polarized component caused by an unwanted mode. An approximate calculation of the power in this mode is given. A simple formula for the input reflection coefficient is provided. Results are included that show how to compute mode conversion in a conical taper, cross polarization from a corrugated horn, including contributions from spurious modes, and the reflection coefficient from the smooth-guide to corrugated-guide transition. Comparison of theory and experiment shows good agreement.