6 research outputs found
Integrated radio frequency synthetizers for wireless applications
This thesis consists of six publications and an overview of the research topic, which is also a summary of the work. The research described in this thesis concentrates on the design of phase-locked loop radio frequency synthesizers for wireless applications. In particular, the focus is on the implementation of the prescaler, the phase detector, and the chargepump.
This work reviews the requirements set for the frequency synthesizer by the wireless standards, and how these requirements are derived from the system specifications. These requirements apply to both integer-N and fractional-N synthesizers. The work also introduces the special considerations related to the design of fractional-N phase-locked loops. Finally, implementation alternatives for the different building blocks of the synthesizer are reviewed.
The presented work introduces new topologies for the phase detector and the chargepump, and improved topologies for high speed CMOS prescalers. The experimental results show that the presented topologies can be successfully used in both integer-N and fractional-N synthesizers with state-of-the-art performance.
The last part of this work discusses the additional considerations that surface when the synthesizer is integrated into a larger system chip. It is shown experimentally that the synthesizer can be successfully integrated into a complex transceiver IC without sacrificing the performance of the synthesizer or the transceiver.reviewe
Uniform framework for the objective assessment and optimisation of radiotherapy image quality
Image guidance has rapidly become central to current radiotherapy practice. A
uniform framework is developed for evaluating image quality across all imaging
modalities by modelling the ‘universal phantom’: breaking any phantom
down into its constituent fundamental test objects and applying appropriate
analysis techniques to these through the construction of an automated analysis
tree. This is implemented practically through the new software package
‘IQWorks’ and is applicable to both radiotherapy and diagnostic imaging.
For electronic portal imaging (EPI), excellent agreement was observed with
two commercial solutions: the QC-3V phantom and PIPS Pro software (Standard
Imaging) and EPID QC phantom and epidSoft software (PTW). However,
PIPS Pro’s noise correction strategy appears unnecessary for all but the highest
frequency modulation transfer function (MTF) point and its contrast to noise
ratio (CNR) calculation is not as described. Serious flaws identified in epid-
Soft included erroneous file handling leading to incorrect MTF and signal to
noise ratio (SNR) results, and a sensitivity to phantom alignment resulting in
overestimation of MTF points by up to 150% for alignment errors of only ±1
pixel.
The ‘QEPI1’ is introduced as a new EPI performance phantom. Being a simple
lead square with a central square hole it is inexpensive and straightforward to
manufacture yet enables calculation of a wide range of performance metrics at
multiple locations across the field of view. Measured MTF curves agree with
those of traditional bar pattern phantoms to within the limits of experimental
uncertainty. An intercomparison of the Varian aS1000 and aS500-II detectors
demonstrated an improvement in MTF for the aS1000 of 50–100% over the
clinically relevant range 0.4–1 cycles/mm, yet with a corresponding reduction
in CNR by a factor of
p
2. Both detectors therefore offer advantages for different
clinical applications.
Characterisation of cone-beam CT (CBCT) facilities on two Varian On-Board
Imaging (OBI) units revealed that only two out of six clinical modes had been
calibrated by default, leading to errors of the order of 400 HU for some modes and materials – well outside the ±40 HU tolerance. Following calibration, all
curves agreed sufficiently for dose calculation accuracy within 2%. CNR and
MTF experiments demonstrated that a boost in MTF f50 of 20–30% is achievable
by using a 5122 rather than a 3842 matrix, but with a reduction in CNR of the
order of 30%.
The MTF f50 of the single-pulse half-resolution radiographic mode of the
Varian PaxScan 4030CB detector was measured in the plane of the detector as
1.0±0.1 cycles/mm using both a traditional tungsten edge and the new QEPI1
phantom. For digitally reconstructed radiographs (DRRs), a reduction in CT
slice thickness resulted in an expected improvement in MTF in the patient scanning
direction but a deterioration in the orthogonal direction, with the optimum
slice thickness being 1–2 mm. Two general purposes display devices were
calibrated against the DICOM Greyscale Standard Display Function (GSDF) to
within the ±20% limit for Class 2 review devices.
By providing an approach to image quality evaluation that is uniform across
all radiotherapy imaging modalities this work enables consistent end-to-end
optimisation of this fundamental part of the radiotherapy process, thereby supporting
enhanced use of image-guidance at all relevant stages of radiotherapy
and better supporting the clinical decisions based on it
Study of spin-scan imaging for outer planets missions
The constraints that are imposed on the Outer Planet Missions (OPM) imager design are of critical importance. Imager system modeling analyses define important parameters and systematic means for trade-offs applied to specific Jupiter orbiter missions. Possible image sequence plans for Jupiter missions are discussed in detail. Considered is a series of orbits that allow repeated near encounters with three of the Jovian satellites. The data handling involved in the image processing is discussed, and it is shown that only minimal processing is required for the majority of images for a Jupiter orbiter mission
Proceedings of the 2004 Coal Operators\u27 Conference
Proceedings of the 2004 Coal Operators\u27 Conference. All papers in these proceedings are peer reviewed in accordance with The AUSIMM publication standard
The Telecommunications and Data Acquisition Report
Archival reports are given on developments in programs managed by JPL's Office of Telecommunications and Data Acquisition (TDA), including space communications, radio navigation, radio science, ground-based radio and radar astronomy, and the Deep Space Network (DSN) and its associated Ground Communications Facility (GCF) in planning, supporting research and technology, implementation, and operations. Also included is TDA-funded activity at JPL on data and information systems and reimbursable DSN work performed for other space agencies through NASA. In the search for extraterrestrial intelligence (SETI), implementation and operations for searching the microwave spectrum are reported. Use of the Goldstone Solar System Radar for scientific exploration of the planets, their rings and satellites, asteroids, and comets are discussed