Time Domain Reflectometry, Conformal Mapping and Ultrawideband Antenna Design

Antennas, particularly broadband and ultrawideband antennas, may be thought of as impedance transformers coupling between a guided wave along a transmission line and free space radiation. This paper examines time domain reflectometry(TDR) as a diagnostic technique for evaluating and localizing the impedance properties of both transmission line and electrically-small antennas. Conformal mapping allows us to calculate the geometry-dependent impedance properties of transmission line. The example of a “semi-coaxial” horn antenna illustrates the utility of the technique. TDR and conformal mapping are complementary experimental and theoretical analysis tools of great value to the antenna designer.