Fat dipole antenna with broadband balun using CPW-to-slotline field transformation

Presented is a fat dipole antenna having square radiating elements fed by a broadband balun based on coplanar-waveguide (CPW)-to-slotline field transformation followed by multi-section slotlines for impedance transformation. The measured results of the broadband balun show a passband of 500 MHz to 5 GH and insertion loss less than 1 dB. The amplitude imbalance is approximately 0.38 dB and the phase imbalance is less than 4.5^o over the entire operation range. In this design, by co-designing the radiating element with the broadband balun, a fat dipole antenna covering from 3 to 5 GHz with an omnidirectional radiation pattern and a maximum gain of 2 dBi is designed, while retaining a size of 38.9 × 80.6 mm.