Novel class of micromachined antennas on high- and low-resistivity silicon for mm-wave applications

Abstract

Micromachining technology is very attractive for integrated antennas as it offers efficient packaging, high radiation efficiency, wide impedance bandwidth, and low mutual coupling between antenna elements. Such advantages are difficult to be achieved using the conventional planar technology especially at high frequencies due to the excitation of surface waves inside the substrate. This research focuses on designing novel class of micromachined antennas operating at 60 GHz using a new fabrication technique. The proposed antenna designs have several advantages. First, the antenna is isolated from the feeding circuit by a ground plane and hence the radiation pattern does not affect the performance of the feeding circuit. Second, the proposed antenna and the feeding circuit are both fabricated on a single substrate using three etching steps and two deposition steps. In the proposed configuration there is no need for hybrid integration or wafer bonding. For the sake of being suitable for different applications, a family of antennas that provides diversity in polarization and radiation pattern properties is presented in this thesis. The members of this family are: single element for linear polarization, single element for circular polarization, reconfigurable element for pattern diversity, reconfigurable element for polarization diversity, dual-band antenna, and wire-grid antenna array. For all designs, high- and low-resistivity silicon substrates are considered. The former solution offers superior electromagnetic performance such as high radiation efficiency and gain, which makes it suitable for medium and long-range wireless systems. On the other hand, the later solution is much cheaper and more compatible with the driving electronics. Its limited gain makes it suitable for short-range wireless systems. The antenna designs are optimized using HFSS and results of the optimum designs are validated using CST. Simulation results demonstrate that the proposed novel antennas have very good frequency response as well as appealing radiation patterns. These characteristics are verified by the very good agreement between HFSS and CST. Generally, the single antenna elements have efficiencies above 90% (30%) for the high- (low-) resistivity silicon substrates whereas the gain is above 7 dBi (3 dBi). As for the wire-grid antenna array presented in the thesis, the efficiency and gain recorded are 86% (22%) and 13 dBi (7 dBi), respectively.