Low-cost, compact UWB antenna with frequency band- notch function

Low-cost, compact, circular planar dipole UWB antennas have been designed, based on the ‘two-penny dipole’. One of the dipole arms has been integrated with the ground plane of a microstrip transmission line, the strip being connected to the other dipole arm. The use of microstrip in stead of stripline technology hardly degrades the radiation characteristics, but simplifies the antenna architecture considerably. Up to 6GHz the azimuthal gain variation does not exceed 3dB. For frequencies in excess of 6GHz the antenna becomes too long, resulting in the forming of elevational lobes and large azimuthal gain variations. Shortening the antenna, results in gain-uniformity in azimuth for high frequencies at the cost of a resonance shift beyond 3GHz. As shown by the first full-wave simulations, this shortening may be realised without compromising the in-band return loss specifications. First measurements performed with antennas realised on FR4 – although hindered by cable-current effects – indicate the correctness of this approach. By inserting a slot in the upper arm of the dipole or inserting a spurline filter in the microstrip part of the antenna, a stop band from 5GHz to 6GHz may be realised.