An extremely wideband tapered balun for application in tightly coupled arrays

This paper presents the design of a single layer, compact, tapered balun with a >20:1 bandwidth and less than λ/17 in length at the lowest frequency of operation. The balun operates from 0.7GHz to over 15GHz. It can provide both impedance transformation as well as a balanced feed for tightly coupled arrays. Its performance is compared with that of a full-length balun operating over the same frequency band. There is a high degree of agreement between the two baluns.