Novel Design of Proximity-fed Ultra-wide Band Annular Slot Antenna

A novel design of a proximity-fed annular slot antenna for UWB operation is pre- sented. Difierent techniques are used to introduce a band rejection to the operated frequency band of the proposed prototype antenna. The antenna consists of a circular radiating patch placed non-concentrically inside a circular ground plane aperture. The patch is proximity-fed by a microstrip line on the other side of the substrate. This conflguration provides an UWB performance in the frequency range of 2.85 to 7.95GHz with relatively stable radiation param- eters. Three difierent techniques to construct a resonant circuit are investigated to achieve the band-notch property in the 5.0{6.0GHz band corresponding to the existing WLAN and HIPER- LAN/2 networks. In the flrst technique, a single complementary split ring resonator (CSRR) and in the second technique, a complementary spiral loop resonator (CSLR) is etched ofi the circular patch. Whereas, in the third technique, a U-shaped slot is etched ofi the microstrip line. These resonators provide the band-notch property without degrading the UWB performance of the pro- totype antenna. Furthermore, the band-notched resonance frequency and the bandwidth can be easily controlled by adjusting the dimensions of the slots. The proposed antenna is simulated, using Zeland IE3D. The prototype antenna is fabricated and the measured data of the return loss versus frequency show very good agreement with the simulated results. The performance of the antenna is analyzed using parametric study to investigate the tuning efiects of the resonator parameters on the impedance matching. The proposed antenna has a simple shape and provides almost omnidirectional fleld patterns, relatively ∞at gain and high radiation e-ciency over the entire operated UWB frequency band excluding the rejected band. Satisfactory antenna perfor- mance with a simple structure and small size makes the proposed proximity-feed antenna a good candidate for UWB.