Performance comparison of micromachined antennas optimized at 5 GHz for RF energy harvester

Abstract

This paper presents a comparative performance of the antennas fabricated using bulk micromachining and surface micromachining process. The dielectric permittivity of crystal silicon (Si) and glass are ɛr = 11.9 and ɛr = 4.7, respectively are considered in the substrates comparison studied. The research aims to discover the best antenna performance by alternative micromachining modes for integrating with the RF harvester printed circuit design. Here, the study on micromachining process method involves the simulation study of three different structures and materials, such as Si with air gap, Si surface and glass surface based antenna. These antennas have been modelled using CST-MWS software. The micromachined antennas have been optimized operating at 5 GHz band. The parameters such as S-parameter, -10 dB bandwidth, radiation pattern, gain, directivity and VSWR are evaluated. The outcomes validate good characteristic of glass based surface micromachined antenna over the Si based for both bulk micromachined and surface micromachined antenna. The results show that the Si surface micromachined antenna is not able to reach the requirement for RF antenna specification, however, it is improved by creating the air cavity. Furthermore, the use of glass substrate has increased the antenna gain by 5.34% and the -10 dB bandwidth increased by 72.86% compared to the Si with air cavity. The glass based antenna dimension is reduced by 9.09% and 44.93% compared to Si bulk micromachined and Si surface micromachined antenna, respectively. Thus, the characteristics of the glass surface micromachined antenna are relatively appropriate for highly efficient RF energy harvester application