An ultra wideband, 1–20 GHz balun in an electrically small conducting enclosure

Balanced antenna radiators require a balun feed circuit which provides equal power split and differential phase to each of the two radiator arms. As antenna radiator bandwidths have increased, balun circuits have increasingly wide bandwidth requirements. This paper presents an improved 1-20 GHz printed circuit balun, designed to operate in an electrically small conducting enclosure whose largest dimension is only 10.6% of a wavelength at the lowest frequency. The paper includes a brief presentation of the improved design, details of the prototype hardware, and a comparison between the numerical simulations and measured prototype performance.