Mobile device antenna design & isolation technologies

Mobile device antenna design and isolation technologies are thoroughly investigated in this thesis. The antenna design parameters for mobile devices are quantified using practical restraints by analyzing almost 60 mobile handsets and the effect of materials, human tissue, manufacturing, and antenna type/placement on antenna design and then mapped into Wheeler-space that correlates the spherical wave modes with the antenna performance. The isolation technologies with mutual coupling anti-resonances are unified by a single performance parameter to distinguish them from the more traditional isolation technologies. This unifying performance parameter is the group delay between two antennas where high group delay indicates the presence of a bandstop filter in the form of either a PCB or an antenna modification. This thesis analyzes both PCB and antenna modifications with high group-delay and demonstrates these types of antennas can be placed in close proximity without affecting other performance parameters. It is also shown that both the PCB and antenna modifications contain two isolation methods where each isolation method is a mirror complement of the other method. Some antenna geometries can also increase the mutual coupling in order to improve the antenna performance using a phenomena called over-coupling. These over-coupled antenna systems can result in lower SAR for the cellular antennas and decreased array sizes for NFC/RFID/wireless-power antennas, resulting in better performance of antennas inside mobile devices.published_or_final_versionElectrical and Electronic EngineeringDoctoralDoctor of Philosoph

Compact low-profile antennas for mobile communications

In recent years, countries throughout the world have agreed to allocate the frequency band 1.7 → 2.1 for future personal communications systems (PCS). Handsets are expected to decrease in size and cost as the circuits and antenna components scale down. The size of the handset is primarily limited by the antenna length and the battery. The ability of multiple antennas on the handset to improve data transfer reliability increases the need for compact antennas. Although the PCS system will reduce the antenna length by a factor of 2 from the current 9OOMHz cellular system, the handset will also scale down and the need for small antennas remains. In the past, cellular handsets employed a (shielded) monopole for transmitting and receiving data. Recently, efforts have been focused on several new designs, including the planar inverted F antenna (PIFA) with a resonant wavelength of λ/4. There exist a variety of techniques to reduce the physical length of the antenna. Dielectrics can increase the electrical length of the antenna by [square root]εr, therefore decreasing the physical length by [square root]εr. Increasing the dielectric constant to reduce the antenna's physical length, however, is cost-prohibitive. Another method involves the use of strategically placed inductive and capacitive loads on the antenna structure. An inductive load is difficult to manufacture as the resonance properties are sensitive to the pitch and spacings between the coils. A capacitive load increases the resonant resistance and reactance, decreasing the probability of achieving a 50ω match. In this thesis, we design a new antenna with length λ/8 for PCS applications. The Finite Difference Time Domain method is used in the design process and results from a prototype are used to verify the findings

Capacitively loaded PIFA

A planar inverted-F antenna is described that is provided with a capacitive load that allows the dimensions of the antenna to be reduced from a conventional λ/4 to λ/8. To maintain good bandwidth and impedance matching in spite of the presence of the capacitive load, a capacitive feed is also provided

'Voyaging in': colonialism and migration

A major reference chapter on the history of the literature of colonialism and migration 1945-70. The book marks an intervention into conventional histories of British Literature. The chapter illustrates and analyses the influential formation of alternative modernities by migrant writers resident in Britain during this period; it also extends the gaze to the period before 1945 earlier in the twentieth century. Maps new ways of reading literary history; broad and wideranging discussion of migration during this period

Reservoir quality of Cenozoic carbonate buildups and coral reef terraces

Almost half of SE Asia's considerable hydrocarbon reserves are contained in carbonates. The majority of these reservoirs are Miocene buildups up to tens of kilometres across. However, with the exception of a few fields, there is little detailed data on how local depositional and diagenetic conditions influence the considerable heterogeneities in reservoir quality often encountered. This study focuses on factors influencing the facies, diagenetic and reservoir variability of comparable Modern, Quaternary and Neogene reef associated deposits from the Tukang Besi Archipelago, Central Indonesia.The Archipelago includes large atolls, a number of smaller buildups and 4 main islands each with modern rimmed shelves or fringing reefs. On the islands, over ten late Neogene and Quaternary coral reef terraces have been uplifted to maximum heights of ~300 m. Analysis of the modern deposits allows initial reservoir potential to be assessed and related to local environmental conditions. The influence of diagenesis on final reservoir quality is evaluated for the depositional facies exposed in the uplifted terraces. The overall spatial distribution of effective porosity across the area is strongly dependent on local energy conditions, water depth, carbonate producers, size of atolls or islands, climate and local meteoric diagenetic processes. This evaluation of spatial variability in carbonate reservoir characteristics provides much needed analogue data as the hydrocarbon industry focuses on improving recovery from existing fields and exploring for new reserves