Design and Construction of UWB Antennas

Abstract| We present design results of two cases of Ultra Wide Band (UWB) quasi circularpatch antennas, one with coplanar feeding (CPW) and the other one with microstrip feeding.Both antennas are an evolution from a circular patch structure softening the edges to improve theantenna performance, agreeing with the theory proposed Kraus. After the evolution there wereimprovements concerning re°ection coe–cient and number of resonant frequencies throughoutthe operating bandwidth. The operational frequency range is from 500MHz to 15GHz using adesign frequency of 4.5GHz. The antenna feeding impedance is proposed to be 50ohms. Theantennas with the best simulation response are constructed to test the practical performance ofexperiment.1. INTRODUCTION The technique to increase the bandwidth (BW) of circular antenna was proposed by Kraus in1988 [1], by smoothing the transition between feed line and the antenna; this technique is easilyapplied to patch antennas with microstrip or coplanar feeding; radiator patch and ground planecan provide an almost constant input impedance over wide bandwidthsRadiating elements patches of printed antennas have a variety of forms, as triangular, rectan-gular, square, elliptical, circular, among others [2,3]. However, it has been found that circularstructures have smaller dimensions related with the operation frequency [4], Moreover, the circularstructure ofiers another important advantage: the only control variable for the structure design isthe patch radius, that is the reason circular or disk antennas are very popular and widely usednowadays.Recently some techniques have been developed to improve BW of circular planar antenna, asintroducing a slot into the circular patch, adding new resonant frequencies. We propose in this papera smooth transition between the circular planar antenna and the ground plane and the microstripfeeding, as was originally established by Kraus in histheoretical volcano smoke antenna [1]. Westart with the design of a circular patch antenna working in a frequency of 4.5GHz.