Circular dipole antennas for lower and upper UWB bands with integrated balun

Two fully integrated dipole antennas with balun for ultra-wideband (UWB) radio utilizing a flexible and rigid printed circuit board are presented in this paper. The concept in this paper is to take advantage of the respective possibilities of the rigid and the flexible part. The balun utilizes broadside-coupled microstrips and is integrated in the rigid part of the printed circuit board, while the radiator is placed in the flexible part. The lower UWB band antenna with the balun covers the frequency-band 3.1-4.8 GHz (with margin) at VSWR<2.0. The upper UWB band antenna with the balun covers the frequency-band 6.0-8.5 GHz (with margin) at VSWR<2.0, and 5.5-11.0 GHz at VSWR<2.5.