A planar antenna with a broadband feeding structure is presented and analyzed for ultrawideband applications. The proposed antenna consists of a suspended radiator fed by an n-shape microstrip feed. Study shows that this antenna achieves an impedance bandwidth from – GHz (48%) for a reflection of coefficient and an average gain of dBi. Stable boresight radiation patterns are achieved across the entire operating frequency band, by suppressing the high order mode resonances. This design exhibits good mechanical tolerance and manufacturability | 2172 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION VOL. 57 NO. 7 JULY 2009 Communications A Planar UWB Antenna With a Broadband Feeding Structure Wee Kian Toh Zhi Ning Chen and Xianming Qing Abstract A planar antenna with a broadband feeding structure is presented and analyzed for ultrawideband applications. The proposed antenna consists of a suspended radiator fed by an n-shape microstrip feed. Study shows that this antenna achieves an impedance bandwidth from GHz 48 for a reflection of coefficient of Sn 10 dB and an average gain of dBi. Stable boresight radiation patterns are achieved across the entire operating frequency band by suppressing the high order mode resonances. This design exhibits good mechanical tolerance and manufacturability. Index Terms Broadband antennas microstrip patch antennas suspended plate antennas ultrawideband UWB antennas. I. Introduction A low profile and embeddable unidirectional antenna is required for certain ultrawideband UWB 1 communication imaging localization and radar applications. The lower and upper UWB spectrums are GHz 43 and GHz 55 respectively. The existing broadband directional antennas such as the Vivaldi 2 log-periodic cavity-backed waveguide horn and dish antennas cover the entire GHz band 109 . However they are electrically large and have a high profile in the direction of wave propagation. Omni- and bi-directional antennas such as the planar monopoles 3 - 5 disc cone 6 and slot antennas 7 have a low gain and back radiation pattern therefore they are not suitable for sectorial or unidirectional communication. Also it is a challenge to maintain a stable radiation pattern across the whole frequency band since the radiation aperture is frequency dependent. To lower the Q-value for increasing the impedance bandwidth of the patch antenna the dielectric substrate is replaced by air the patch is usually suspended at a height of where Ao is the free .
