Design and construction of a printed antenna for wireless terminals in the unlicensed 5GHz bands

Abstract

At the time of writing, wireless mobile data terminals were proliferating. The principal motor behind the ready availability of such terminals is the IEEE 802.11 family of standards, of which IEEE 802.1 la is the member concerned with transmissions in the to-date unlicensed bands in the 5-6 GHz region. ETSI HIPERLAN Type 1 and Type 2 are two other families of standards for wireless mobiles that also require a wideband antenna in this region. A design is sought for these applications. The design problem is tackled starting from an appreciation of the physical properties of the structure, referred to as a printed inverted-L, antenna (PTLA). Its input impeccancy property is then investigated using an FDTD simulator, which includes a near-far field transformation tool for acquisition of radiated field data. The finished product should be inexpensive, compact and robust. Costs are controlled by the use of a simple manufacturing process. Compactness is achieved through the use of a high-bandwidth structure, a substantially high relative dielectric constant and meandering of the current path. Robustness is implemented through an antenna array in which each element is laid out to receive a signal uncorrelated to that of its peers under multipath conditions. The robustness is verified using simulation data and a model that is well documented in literature [45,48,49]. An alternative means of characterising the robustness of antennas for these applications is recommended [43].