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This thesis describes the theoretical and practical implementation of a long-range high-resolution millimetre wave imaging radar system to aid with the navigation and guidance of both airborne and ground-based autonomous vehicles. To achieve true autonomy, a vehicle must be able to sense its environment, comprehensively, over a broad range of scales. Objects in the immediate vicinity of the vehicle must be classified at high resolution to ensure that the vehicle can traverse the terrain. At slightly longer ranges, individual features such as trees and low branches must be resolved to allow for short-range path planning. At long range, general terrain characteristics must be known so that the vehicle can plan around difficult or impassable obstructions. Finally, at the largest scale, the vehicle must be aware of the direction to its objective. In the past, short-range sensors based on radar and laser technology have been capable of producing high-resolution maps in the immediate vicinity of the vehicle extending out to a few hundred metres at most. For path planning, and navigation applications where a vehicle must traverse many kilometres of unstructured terrain, a sensor capable of imaging out to at least 3km is required to permit mid and long-range motion planning. This thesis addresses this need by describing the development a high-resolution interrupted frequency modulated continuous wave (FMICW) radar operating at 94GHz. The contributions of this thesis include a comprehensive analysis of both FMCW and FMICW processes leading to an effective implementation of a radar prototype which is capable of producing high-resolution reflectivity images of the ground at low grazing angles. A number of techniques are described that use these images and some a priori knowledge of the area, for both feature and image based navigation. It is shown that sub-pixel registration accuracies can be achieved to achieve navigation accuracies from a single image that are superior to those available from GPS. For a ground vehicle to traverse unknown terrain effectively, it must select an appropriate path from as long a range as possible. This thesis describes a technique to use the reflectivity maps generated by the radar to plan a path up to 3km long over rough terrain. It makes the assumption that any change in the reflectivity characteristics of the terrain being traversed should be avoided if possible, and so, uses a modified form of the gradient-descent algorithm to plan a path to achieve this. The millimetre wave radar described here will improve the performance of autonomous vehicles by extending the range of their high-resolution sensing capability by an order of magnitude to 3km. This will in turn enable significantly enhanced capability and wider future application for these systems.

This thesis describes the theoretical and practical implementation of a long-range high-resolution millimetre wave imaging radar system to aid with the navigation and guidance of both airborne and ground-based autonomous vehicles. To achieve true autonomy, a vehicle must be able to sense its environment, comprehensively, over a broad range of scales. Objects in the immediate vicinity of the vehicle must be classified at high resolution to ensure that the vehicle can traverse the terrain. At slightly longer ranges, individual features such as trees and low branches must be resolved to allow for short-range path planning. At long range, general terrain characteristics must be known so that the vehicle can plan around difficult or impassable obstructions. Finally, at the largest scale, the vehicle must be aware of the direction to its objective. In the past, short-range sensors based on radar and laser technology have been capable of producing high-resolution maps in the immediate vicinity of the vehicle extending out to a few hundred metres at most. For path planning, and navigation applications where a vehicle must traverse many kilometres of unstructured terrain, a sensor capable of imaging out to at least 3km is required to permit mid and long-range motion planning. This thesis addresses this need by describing the development a high-resolution interrupted frequency modulated continuous wave (FMICW) radar operating at 94GHz. The contributions of this thesis include a comprehensive analysis of both FMCW and FMICW processes leading to an effective implementation of a radar prototype which is capable of producing high-resolution reflectivity images of the ground at low grazing angles. A number of techniques are described that use these images and some a priori knowledge of the area, for both feature and image based navigation. It is shown that sub-pixel registration accuracies can be achieved to achieve navigation accuracies from a single image that are superior to those available from GPS. For a ground vehicle to traverse unknown terrain effectively, it must select an appropriate path from as long a range as possible. This thesis describes a technique to use the reflectivity maps generated by the radar to plan a path up to 3km long over rough terrain. It makes the assumption that any change in the reflectivity characteristics of the terrain being traversed should be avoided if possible, and so, uses a modified form of the gradient-descent algorithm to plan a path to achieve this. The millimetre wave radar described here will improve the performance of autonomous vehicles by extending the range of their high-resolution sensing capability by an order of magnitude to 3km. This will in turn enable significantly enhanced capability and wider future application for these systems.

Millimetre-wave nonreciprocal devices are vital elements in many modern radar and communication systems. Gyromagnetic behaviour in magnetised ferrite materials has been utilised for decades in the design of nonreciprocal devices. However, the effects of ferrite's limited saturation magnetisation and high loss as the frequency of operation exceeds 40 GHz render such devices inadequate for millimetre-wave applications. On the other hand, solid plasma (such as semiconductors) are known to exhibit gyrotropic behaviour when they are biased with a steady magnetic field. This behaviour (which is referred to as gyroelectric) can extend up to the THz frequency ranges. Hence, magnetised semiconductors can be regarded as suitable candidates for realising millimetre-wave, sub-millimetre-wave and even THz nonreciprocal devices. This thesis focuses on analysing different structures containing gyroelectric materials, and proposing millimetre-wave nonreciprocal devices based on the theoretical findings. Measurements and full wave electromagnetic simulation are used to validate and optimise the proposed designs where possible. Before starting the electromagnetic analysis, the physical properties of a semiconductor plasma are studied, then a permittivity tensor is introduced to include the microscopic features of the magnetised semiconductors into a macroscopic model. Different semiconductor candidates for gyroelectric designs are also discussed and analysed. Firstly, Semiconductor Junction Circulators (SJC's) are analysed using a Green's function approach. The same approach is then used to proposed new designs for broadband millimetre-wave SJC's that require low magnetic bias using Indium Antimonide (InSb) cooled down to 77 K. The possibility of realising planar nonreciprocal devices using a Molecular Beam Epitaxy (MBE) grown Two Dimensional Electron Gas (2-DEG) is also studied. Theoretical and simulation results prove the possibility of using this material to realise millimetre-wave resonators and circulators. Then a novel type of circulator is realised by placing an InSb disk at 77 K in the middle of a three port waveguide junction. The structure is analysed by treating the junction as a resonator with a suspended axially magnetised gyroelectric rod placed in the middle. Electromagnetic analysis, simulations and measurements reveal the existence of counter rotating modes that degenerate or split at certain frequencies under specific magnetic bias conditions. Measuring this circulator reveals an isolation of 18 dB at 38.5 GHz when the InSb disk is biased with a D.C. magnetic flux of 0.55 T. This is the first time such a circulator has been demonstrated theoretically and experimentally. In addition to the three port circulator, a model is developed for a rectangular waveguide loaded with layered dielectric and gyroelectric media. Mathematical analysis reveals the dispersion relations and field distributions for such a structure. High nonreciprocity in both phase and attenuation constants is observed from analysing a rectangular waveguide loaded with a transversely biased InSb slab at 77 K. The expected nonreciprocity is then verified, for the first time, by simulation and measurement of similar structures under the same conditions. More than 35 dB of isolation at f=35.6 GHz was obtained when loading a WR-28 rectangular waveguide with an InSb slab at 77 K, transversely biased with a magnetic flux of 0.8 T. Different effects on the isolation behaviour are also discussed theoretically and experimentally, including the effects of the slab's thickness and length, the magnetic bias and the existence of a dielectric layer above the gyroelectric slab. Theoretical and experimental outcomes of this thesis prove the possibility of using gyroelectric materials to develop a new class of component that meets the demands for millimetre-wave nonreciprocal devices. This will provide a significant improvement to the modern high frequency millimetre-wave systems.

No description available.

The millimetre-wave (mm-wave) spectrum offers considerable advantages in terms of antenna form factor and spectrum availability. However, use of this region often requires reconfigurable antennas and systems. Initially, a review of the various applications which are taking hold in the lower regions of the mm-wave spectrum (30 to 100 GHz) is undertaken. Specifically, reconfigurable reflectarray technologies are selected for further research, and critical analysis of the reconfiguration techniques for including these in antennas is considered. Silicon as an optically activated semiconductor is chosen as the reconfiguration mechanism due to its low cost and the scope for improvement in this area. A new form of illumination is used, replacing traditional infra-red (IR) lasers with high power IR-LEDs enclosed in a cavity, increasing the efficiency of the silicon illumination. However, to make use of this novel illumination source, and subsequently integrate it into an antenna, the silicon response has to be characterised within Ka-band. This is done through measurements in a waveguide-based characterisation test cell, from which the complex electromagnetic properties of silicon under IR-LED illumination are retrieved with the aid of full-wave simulations. Using the measured conductivity properties of the illuminated silicon, reflectarrays with non-uniform amplitude distributions can be designed. Through variation of illumination intensities of IR-LEDs throughout the array, it is shown through measurements and full-wave simulations that unit cell reflections can be modified while phases are kept relatively constant. This theoretically allows switching between, for example a low side-lobe pattern binomial array, or a narrow beamwidth pattern Chebyshev array. To implement this, a novel multilayer unit-cell is designed, integrating the IR-LED. This is then used in a full reflectarray design which is measured. The key contributions of this work include the novel illumination mechanism and its integration into a reflectarray antenna, and the use of reconfigurable photoconductive materials to provide a mechanism for beam shaping and pattern synthesis at Ka-band.

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.

The scope of this work is the development of a 60 GHz flexible transceiver frontend by adopting an economic prototyping approach. Such a platform can validate the proposed protocols for the 60 GHz band in a real wireless environment, especially the physical layer security concept. The development course uses the hybrid architecture with off-the-shelf components and custom-designed RF chain blocks on printed circuit technology. Challenge in this approach is the coarse resolution of the selected manufacturing technology and higher process tolerance. This work extends the state-of-the-art by proposing etching-resilient RF chain blocks on wide bandwidths. It presents the design validation of each block and performance analysis for various manufacturing conditions. The study also reviews and proposes a high-frequency interconnect model for bondwires, vital in a frontend design. Parasitics' compensation of the interconnects at millimeter-wave operation is proposed, compatible with printed circuit technology. The 60 GHz frontend is realized by packaging the designed RF blocks and off-the-shelf components with optimized and characterized high-frequency interconnects. The frontend, equipped with a tailor-made antenna duplexer, is reconfigurable for frequency, power, and modulation scheme. The developed frontend is characterized for local oscillator, transmitter, and receiver operations. The adaptability of the frontend allows it to be used as an agent in a heterogeneous network. Two units of the developed frontends are used in a network for frequency domain channel sounding. The antenna duplexer ensures channel reciprocity in bidirectional sounding campaigns. Matched two-way channel response is achieved in various indoor environments, which endorses the frontend for channel reciprocity key generation. Finally, the frontend units are successfully deployed in a physical layer security demonstrator.:Abstract Chapter1: Introduction Chapter 2: Fundamentals and state-of-the-art Chapter 3: The design Chapter 4: Integration and characterization Chapter 5: Application example: Channel sounder Chapter 6: Summary and future work Appendices Bibliography

Despite its importance the fundamental question of how massive stars form remains unanswered, with improvements to both models and observations having crucial roles to play. To quote Bate et al. (2003) computational models of star formation are limited because “conditions in molecular clouds are not sufficiently well understood to be able to select a representative sample of cloud cores for the initial conditions”. It is this notion that motivates the study of the environments within Giant Molecular Clouds (GMCs) and Infrared Dark Clouds (IRDCs), known sites of massive star formation, at the clump and core level. By studying large populations of these objects, it is possible to make conclusions based on global properties. With this in mind I study the dense molecular clumps within one of the most massive GMCs in the Galaxy: the W51 GMC. New observations of the W51 GMC in the 12 CO, 13 CO and C18 O (3 – 2) transitions using the HARP instrument on the JCMT are presented. With the help of the clump finding algorithm CLUMPFIND a total of 1575 dense clumps are identified of which 1130 are associated with the W51 GMC, yielding a dense mass reservoir of 1.5 × 105 M contained within these clumps. Of these clumps only 1% by number are found to be super-critical, yielding a super-critical clump formation efficiency of 0.5%, below current SFE estimates of the region. This indicates star formation within the W51 GMC will diminish over time although evidence from the first search for molecular outflows presents the W51 GMC in an active light with a lower limit of 14 outflows. The distribution of the outflows within the region searched found them concentrated towards the W51A region. Having much smaller sizes and masses, obtaining global properties of clumps and cores within IRDCs required studying a large sample of these objects. To do this pre-existing data from the SCUBA Legacy Catalogue was utilised to study IRDCs within a catalogues based on 8 µm data. This data identifies 154 IRDC cores that are detected at 850 µm and 51 cores that were not. This work suggests that cores not detected at 850 µm are low mass, low column density and low temperature cores that are below the sensitivity limit of SCUBA at 850 µm. Utilising observations at 24 µm from the Spitzer space telescope, allows for an investigation of current star formation by looking for warm embedded objects within the cores. This work reveals 69% of the IRDC cores have 24 µm embedded objects. IRDC cores without associated 24 µm emission (“starless” IRDC cores) may have yet to form stars, or may contain low mass YSOs below the detection limit. If it is assumed that cores without 24 µm embedded sources are at an earlier evolutionary stage to cores with embedded objects a statistical lifetime for the quiescent phase of a few 103 – 104 years is derived.

Studying the orbital angular momentum (OAM) of light has become rather fashion- able in the 21st century. Yet, most of major advances in OAM related research have been conducted in the visible regime of light. A significant portion OAM research revolves around using OAM radiation to perform some function that is deemed useful. Examples of this are optical trapping, micro-machine manipulation and the development of advanced communication systems. Photon entanglement measurements also make use of OAM radiation. Interest in probing radiation for naturally generated OAM is far less popular. For example, interest in building OAM sensitive telescopes was sparse at the beginning of this thesis, however the first reported detection of astrophysical OAM was published in 2013. This thesis aims to tackle these two areas of sparse research by developing the components and understanding in order to build OAM sensitive millimetre-wavelength telescopes. Spiral phase plates (SPPs) are the device of choice. The majority of the thesis sets out to test three different SPPs, in order to compare and contrast different methods for their manufacture and design. Electromagnetic theory of OAM and its generation is reviewed first. Then, each SPP is modelled numerically fol- lowed by in-depth modelling of each plate by using the computational electromagnetic package FEKO. Finally, each plate is measured with a three dimensional field scanner developed as part of this thesis. Development of a new modular SPP design concludes this thesis.