Klopfenstein tapered 2–18 GHz microstrip balun

Tapered microstrip Balun is used as an impedance transformer network in feeding sections of spiral antennas as it provides impedance transformation over a large range of frequency and also serves the purpose of conversion of single ended port to a symmetric port. The conversion from unbalanced to balanced line relies on a gradual change of cross section of the line. This paper presents a 2-18 GHz microstrip Balun that uses the Klopfenstein equations for the taper. The Balun structure was first simulated in Ansoft HFSS and then fabricated; there was a close match between the simulated and measured results.