AbstractThe aim of this work is to design and realise millimetre-wave low profile on-chip antennas for 60 GHz short-range wireless communication systems. For this application, it is highly desirable that the antenna can be compatible with standard silicon complementary metal oxide semiconductor (Si CMOS) technology for high level integration and mass production a low cost. Firstly, millimetre-wave antennas on normal dielectric substrates and cavities were studied in detail in order to better understand how the antenna parameters could have effects on their performance at millimetre-wave spectrum. On-chip 60 GHz antennas based on Si CMOS technology were then proposed, designed, fabricated and characterised. A millimetre-wave U-shaped slot antenna with wide bandwidth was first investigated, simulated and designed. The simulation results reveal that this antenna can operate at millimetre-wave frequencies with 1 GHz bandwidth at 73.5 GHz and 76.5 GHz, respectively. A 60 GHz folded dipole antenna was also studied and designed. A metal cavity was added on the back of a folded dipole antenna to act as reflector. Simulated results show that a folded dipole antenna with a metal cavity can achieve a radiation efficiency of 97.9% at its resonant frequency. Compared to the gain obtained for the folded dipole antenna without a cavity, the antenna gain with metal cavity can be enhanced by 3.58 dB. The main challenges of making high gain and high efficiency Si CMOS on-chip antennas at millimetre-wave spectrum come from two sources; the thin silicon dioxide (SiO2) layer (maximum 10 micrometre) and silicon substrate loss (10 ohmscm). The thin SiO2 layer prevents the use of an elevated ground plane, which could significantly reduce the silicon substrate loss, due to the imaging current effect. Si CMOS substrates normally have resistivity of 10 ohmscm, which is very lossy at millimetre-wave spectrum. To tackle these challenges, metamaterial structures, named artificial magnetic conductor (AMC) structures, were studied and utilised for low profile Si CMOS on-chip antenna design and realisation.AMC forms high impedance on its surface, reflecting the incident wave without phase reversal so as to enhance the radiation efficiency. The AMC folded dipole antenna was designed with a mushroom-shaped structured metamaterial cavity. Simulation results show that the gain increased 1.5 dB in the antenna with AMC structure, while the distance to the metamaterial surface was reduced by 90% compared to that of the pure metal cavity. Additionally, two low profile Si CMOS on-chip antennas with novel planar AMC structures were designed, fabricated and characterised. They were manufactured by 0.13 micro metre Si CMOS technology from Chartered foundry and 0.18 micro metre Si CMOS technology from TSMC, respectively. The techniques proposed in these two antennas provide valuable alternatives to the existing approaches. The measurement results show that bandwidth of the on-chip antenna with a micro-patterned artificial lattice is approximately 10 GHz. The one with a dog-bone shape and uniplanar compact photonic band gap (UC-PBG) structures managed a 1.6 dB gain and 1 GHz bandwidth enhancement compared to that without AMC structures.
|Date of Award||1 Aug 2012|
|Supervisor||Zhirun Hu (Supervisor)|