Summary
International Symposium on Antennas and Propagation
2008
Session Number:2C11
Session:
Number:2C11-1
CPW-fed UWB monopole antenna optimization
Somayyeh Chamaani, Kian Paran, Ali Abolghasemi, Maasum Fardis,
pp.-
Publication Date:2008/10/27
Online ISSN:2188-5079
Summary:
In recent years, useful characteristics of ultra wideband (UWB) technology such as high data rate, low interference with other systems, and resistance to multi path fading propounded it as an interesting method of data communication especially for short distances. For this class of applications, design of light weight and portable UWB devices attracts much interest. In this direction, many studies have been done on antenna as an indispensable part of UWB systems. Through different prototypes, planar antennas due to their integration capability and small size attract much attention. In this paper we focus on planar monopole antenna with a coplanar waveguide (CPW) feed. Planar CPW-fed antenna had been investigated from frequency domain aspects such as VSWR and radiated pattern [1]. In impulse radio UWB communication, consistency of signal waveform from transmitter to receiver must be preserved. Antenna, as an analog part of system, may destroy this consistency. Time-domain response of UWB antennas has been investigated for various input waveforms [2]. In our study, in addition to return loss, transient characteristics of antenna for a fixed waveform which satisfies the Federal Communications Commission (FCC) mask [3] are considered. Fidelity factor as a time domain bench mark could be applied to assess transient performance of antenna. A high fidelity factor means high similarity between transmitted and received signals. In other word, a high fidelity factor ensures flatness of transfer function magnitude ( |S 21| ) and linearity of transfer function phase (∠S 21 ) in frequency domain. A genetic algorithm (GA) optimizer is aimed at minimization of return loss and maximization of fidelity factor. Fidelity factor is calculated by means of three virtual probes situated at proper locations in far field region. Major parts of optimization variables lies on ground part of CPW. In the next section, antenna structure and optimization procedure is described. Section III elaborates simulation results of optimized antenna and compares it with a prototype antenna for different criteria such as VSWR, correlation factor (fidelity factor), transfer function and group delay. Finally conclusions are expressed in section IV.