Compact Microstrip-Fed Annular-Slot Antenna Combined with C-shaped Slot for Broad Dualband Operation

TitleCompact Microstrip-Fed Annular-Slot Antenna Combined with C-shaped Slot for Broad Dualband Operation
Publication TypeConference Paper
Year of Publication2008
AuthorsBao, XL, Ammann, MJ
Conference NameProgress In Electromagnetics Research Symposium
Conference Start Date24/03/2008
PublisherProgress In Electromagnetics Research Symposium
Conference LocationHangzhou, China

Recently, annular-slot antennas have been of great interest to antenna designers because of good performance, such as relatively wide bandwidth, low profle, light weight, and ease of fabrication. Dual-band and multi-band annular-slot antennas had been reported of late and
impedance bandwidths in the range 10% (20% have also been realised by adjusting the feedline and slot structure). In this paper, an antenna comprising a compact annular-slot combined with a small concentric annular split-ring slot is presented. The antenna is fed by a T-shaped microstrip line. By using the T-shaped microstrip feedline to tune the level of electromagnetic coupling between annular-
slot and feedline, good matching can be achieved. The proposed antenna can effectively enlarge the length of the annular-slot by introducing the concentric annular split-ring slot, so it can lengthen the surface current path, thus signifcantly reducing the resonant frequency. For the proposed antenna, the length and width of microstrip feedline and the width of annular-slot are the key parameters which determine the antenna performance because of the electro-magnetic coupling through the strip and slot. By optimizing these parameters, a broadband dual-frequency slot antenna is realised. The measured results of return loss show good agreement with simulated values. The results show that bandwidth for the lower band is about 27.2% (490 MHz) from 1.556 GHz to 2.046 GHz, and the bandwidth for the high band is about 34.1% (1798 MHz) from 4.366 GHz to 6.164 GHz. The ratio of centre frequencies for the lower and high bands is 2.92. The radiation patterns are omnidirectional. The slot antenna is proposed for wireless communication applications which
require broadband dual-frequency operation.

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