The 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 μm Si CMOS technology from Chartered foundry and 0.18 μm 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.

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In this dissertation, the operation of dual-linear polarized antennas is considered in order to provide ideal performance suited for several applications including polarimetric synthetic aperture radar (SAR), wireless and satellite communications. The underlying objectives realized in this work are reported as design realizations of dual-linear polarized antennas with low cross polarization patterns and high isolation between ports that employ special properties of the electromagnetic metamaterial (MTM) structures. Some of these key properties appear as negative permittivity, negative permeability, negative refractive index, and antiparallel nature of the phase velocity and the group velocity. The antenna design is carried out at two frequencies, 5.5 GHz and 10 GHz, and key physical issues that affect the operation of dual-linear polarization operation antennas are treated in light of electromagnetic MTM properties. It’s well known that a dual linear polarized antenna poses a big challenges such as cross polarization patterns and high mutual coupling between two input ports. Therefore, these drawbacks are key topic that receive significant attention in literature which reports on how to mitigate these drawbacks, however, at the expense of complexity of the antenna structures. The MTM structures have received considerable coverage in antenna research for obtaining size reduction, directivity enhancement, and beam steering. For this purpose, different MTMs structures are chosen in this thesis for achieving additional improvements, while keeping the antenna design as simple as possible, something which is very difficult to accomplish using conventional design methods.:Chapter 1: Introduction Chapter 2: Dual linear Polarization Antennas and Arrays Chapter 3: Fundamental Theory of Metamaterials Chapter 4: Metamaterial Structures Design-Methodology Chapter 5: Design of Dual Linear Polarization Using CRLH-TL Metamaterial Line Feed Chapter 6: Cross Polarization Discrimination Enhancement of a Dual Linear Polarization Antenna Using Split Ring Resonator Chapter 7: Antenna Array Design Chapter 8: Conclusions and Future Work / In der folgenden Dissertation wird der Einsatz von zweifach linear polarisierten Antennen zur idealen Ausführung von verschiedenen Anwendungen, einschließlich von polarimetrischen Synthetic Aperture Radar (SAR), kabellose und satellitengestützte Kommunikation, diskutiert. Die Ziele dieser Arbeit werden dargestellt durch die Gestaltung von zweifach linear polarisierten Antennen mit gering Kreuz-Polarisationsmustern und die starke Isolation zwischen den Ports durch die einzigartigen Eigenschaften der Strukturen des elektromagnetischen Metamaterials (electromagnetic metamaterial; MTM). Einige dieser Eigenschaften treten als negative Permittivität, negative Permeabilität, negativer Brechungsindex und als antiparallel Richtungen (Gegenvektor) der Phasen-und Gruppengeschwindigkeit auf. Somit wird die Antennengestaltung auf zwei Frequenzen übertragen, 5,5GHz und 10 GHz, und die Ausführung der zweifach linearen Polarisation wird durch die elektromagnetischen Eigenschaften des MTM illustriert. Weil die Kreuzpolarisationsmuster und starke gegenseitige Koppelung zwischen zwei Input-Ports bei einer zweifach linear polarisierten Antenne große Schwierigkeiten bereiten, werden diese im Großteil der Fachliteratur als Schwerpunkte gesetzt, was zu einer Milderung der Nachteile führte, jedoch dafür die Komplexität der Antennenstruktur zunahm. Die Vielfalt an MTM ist ein bedeutender Teil im Bereich der Antennenforschung einschließlich der Größenverkleinerung, der Verbesserung der Richtcharakteristik und der Strahlensteuerung. Für diesen Zweck werden in dieser Dissertation verschiedenste MTM Strukturen ausgewählt um weitere Verbesserungen der Antennenstruktur zu ermöglichen und gleichzeitig die Einfachheit der Struktur zu bewahren, was mit konventionellen Gestaltungsmethoden nur schwer zu erreichen ist.:Chapter 1: Introduction Chapter 2: Dual linear Polarization Antennas and Arrays Chapter 3: Fundamental Theory of Metamaterials Chapter 4: Metamaterial Structures Design-Methodology Chapter 5: Design of Dual Linear Polarization Using CRLH-TL Metamaterial Line Feed Chapter 6: Cross Polarization Discrimination Enhancement of a Dual Linear Polarization Antenna Using Split Ring Resonator Chapter 7: Antenna Array Design Chapter 8: Conclusions and Future Work