International Journal of Electromagnetics and Applications 2012, 2(6): 145-150 DOI: 10.5923/j.ijea.20120206.02 Design and Analysis of a Compact Printed UWB Antenna Using Non Uniform Matching and Half-Wavelength Circular Slot Mohame d Hayouni 1,* , Fethi Choubani 1 , Tan Hoa Vuong 2 , Jacques David 2 1 Innov’COM, Sup’ COM, University of Carthage, Tunisia 2 ENSEEIHT (France) Abstract In this paper, antenna ultra wideband enhancement by non-uniform matching and half-guided wavelength circular embedded slots is presented and analysed in detail. A printed compact rectangular monopole antenna with two convex circled corners has been analysed firstly. A good impedance matching is achieved in the IEEE radar engineering X-band satellite communications by lowering below -50 dB value at 9.5 GHz. The current density can reach 52 A/m with convex corners; this value is large compared to 32 A/m obtained with stepper corners. In addition, the measured radiation patterns at various frequencies show clearly that the antenna displays nearly an omnidirectional radiation pattern in the E plane (xz) and the H-plane (yz) in both co-and cross-polarizations. The group delay indicates that this antenna is reliable so that a transmitted signal will not be seriously distorted. Two circular half-wavelength slots are embedded in the radiating patch to improve S 11 in the WLAN band. Accordingly ultra-wideband behaviour is achieved along a bandwidth is ranging from 3.5 GHz to 12.5 GHz. Due to its compact size of 30 x 35 mm 2 and its good impedance matching especially in the X band, the designed antenna is able to satisfy some of the requirements of an airborne SAR and is also well suited for remote sensing applications. Keywords Compact Printed Monopole Antenna, Half-Wavelength Circular Slot, Non Uniform Impedance Matching, Ultra-Wideband (UWB) 1. Introduction Since the approval and allocation of the frequency band between 3.1-10.6 GHz[1], miniaturization and bandwidth enhancement become one of the most promising technologies for future high-data rate wireless communication, high accuracy radar and imaging systems. Eventually, the UWB system, the UWB antenna has drawn heavy attention from researchers. Some developments in allied branches are now being investigated to antennas applications. Various recent basic principles of broadband design are deployed in the literature. Indeed, the investigation into the performance of proximity coupled stacked patches by the exploration of the relationship required between the dielectric layers, the dimensions of the stacked radiators and the relative location of the feed can achieve a broadband behaviour in excess of 20% as studied in[2]. The optimization of the impedance matching through narrow cavity backed configuration as described in[3],can * Corresponding author: mohamed hayouni mohamed.hayouni@supcom.rnu.tn (Mohamed Hayouni) Published online at http://journal.sapub.org/ijea Copyright © 2012 Scientific & Academic Publishing. All Rights Reserved enhance the bandwidth of the proposed antenna to more than 40% (VSWR<2) since it can provide a larger effective coupling as compared with the conventionalproximity-coup led antenna without a narrow cavity backed configuration. A low Q factor of the magnetic wall under the patch created by a low dielectric constant or larger thickness of the substrate is also an available broadband technique[4]. The impedance matching of the feed by probe compensation using L-shape probe and any reactive loading as evoked in[5] is also another basic principle of broadband design. In addition by integration slots in the ground plane of microstrip planar antennas as deployed in[6]-[7], or by using a rigged ground plane[8] or slots in the radiator as published in[9]-[12], compact operation with enhanced impedance bandwidth can be obtained. In[13] a printed monopole antenna consisting of a square ring radiating patch with a pair of T-shaped strips protruded inside the square ring and a coupled π–shaped and a ground plane with a protruded strip, provides a wide usable fractional bandwidth of more than 130%. In addition some integrated bandstop filters connected to the UWB antenna are used to reject some narrow bands in order to confront a possible electromagnetic interference, as over the allocated wide bandwidth of the UWB system. The use of U, C and H and semi-circular half wavelength slots embedded in the