Design of Compact Ultrawideband Slot Antenna With Improved Band-Edge Selectivity

A small ultrawideband (UWB) slot antenna is proposed using a stepped impedance resonator feeding line, aiming at improving band-edge selectivity. The proposed antenna mainly comprises a feeding line with low-pass characteristics at the top of the dielectric substrate and two slots at the bottom. The stepped impedance resonator is used to improve the upper band-edge selectivity, and the narrow slot near the stepped slot improves the lower band-edge selectivity. The frequency selection range, the frequency selective characteristic, and the reflected zeros of the antenna upper band-edge are analyzed and studied. The measured results show that the antenna covers the frequency range of UWB systems from 3.1 to 11 GHz (114%) with the reflection coefficient less than -10 dB. Compared with the traditional UWB antenna, the proposed compact antenna has advantages in size and band-edge selectivity and is more suitable for UWB applications. The ratio of the -3 dB bandwidth to the -10 dB bandwidth is 1.038, which is very close to 1.