Rigorous analysis of an impulse radiating antenna with a non-ideal feed structure

The 4:1 equal-delay transformer/balun of an impulse radiating antenna (IRA) is analyzed including the effects of non-commensurate constituent transmission lines. Specifically, we develop a 2-port Th’evenin equivalent source that is compatible with most numerical simulations. It is shown that the noncommensurate balun manifests itself in quasi-periodic frequencydomain ripple in the transfer function of the antenna as well as excitation of the common mode. The analysis combines an analytically-derived 2-port source with a commercial finite element analysis in order to include many details of the device. We believe it is the first such detailed analysis of the feed structure of the IRA.