President's Research Scholarship: PhD in Waveform Engineering (PhD Studentship)
Reference Number: R1096
As part of Cardiff University's President's Research Scholarship scheme we have two exciting PhD projects available in Waveform Engineering for an October 2013 start date.
President’s Scholarships are the University’s flagship scheme for PhD studentships. A key feature of the scheme is the involvement of industrial partners in all projects, allowing each student to benefit from direct interaction with practicing engineers, researchers and managers and including short industrial placement(s) at the collaborating company. President’s Scholarship holders also join a network of students and supervisors, including regular mini-conferences, guest lectures, annual presentations to industrial partners and participation in the School’s annual PGR Conference.
Project 1: Non-linear Modelling From Non-linear Data
Project Title: Non-linear Modelling From Non-linear Data (reference number: PRES6-PJT-2013)
Project Description: Designing very high efficiency power amplifiers for future mobile communication systems requires improved CAD based non-linear models. The development of accurate transistor models has proven to be a very challenging task because of the inadequacies in the RF transistor characterisation tools; dynamic non-linear models being based on static or linear RF measurements. Recently there have been considerable advances in dynamic RF characterization tools, with both researchers at Cardiff University and Agilent technologies taking lead roles in their development. RF characterisation systems now allow for the dynamic RF I-V waveforms measurements. Coupling with active or passive source- and load-pull systems, especially when harmonics are included, allows these RF I-V waveforms to be engineered; Waveform Engineering based characterisation, exploiting load-line design and related excitation design, provides for a whole new approach to non-linear transistor modeling and model extraction. Both will be explored in this project.
Model Extraction: RF Waveform Engineering systems will be used to explore the complete device operating range, in the most efficient way possible. This will provide the data for advanced transistor modeling approaches, such as multi-dimensional artificial neural networks. Engineering the load-lines to transit through specific points in the appropriate device model space at synchronised times will allow the isolation and identification of trap states in III-V transistors. This will allow electro-thermal and trap-related phenomena to be decupled, with a minimum of independent measurements. This is a nonlinear control problem, where the objective is to engineer the excitations needed to establish the device into multiple internal specified states, distributed according to a density that allows for most efficient model training.
Model Development: The project will also investigate frequency-domain nonlinear behavioural models based directly on waveform measurements. The geometrically scalability of this modelling approach has been demonstrated, dramatically enhancing their applicability to MMIC and circuit design. The next step in advancing such nonlinear behavioural models of transistors is to extend the scaling rules to the dimension of frequency.
Project 2: Baseband Linearisation Schemes for High Efficiency Power Amplifiers
Project title: Baseband Linearisation Schemes for High Efficiency Power Amplifiers (reference number: PRES4-PJT-2013)
The global information and communication technology (ICT) industry is a fast growing contributor to worldwide greenhouse gas emissions. The mobile communications sector represents a significant part of this problem with further dramatic increases in growth, power consumption and data volume widely predicted over the next decade. This is due to technologies such as netbooks, tablets and smart-phones increasingly relying on mobile radio networks for internet access, data transmission as well as voice communications. These changes combine to dramatically increase the energy consumption of the mobile networks, and ways must be found to address network power efficiency. One of the prime consumers of energy within these communications systems is the power amplifier (PA), and this research project considers how the performance of this critical component can be optimised.
Practical Waveform Engineering is a RF characterisation technique that allows for the dynamically measured voltage and current waveform behaviour within an active device to be analysed. It is becoming an extremely important tool for optimising device behaviour within PAs. This project explores the novel use of active harmonic and baseband load-pull and source-pull to isolate RF current and voltage (RFI-V) waveforms that promote linearity, whilst at the same time, achieve high-efficiency. It is hoped that this will provide new approaches to linearisation for wide dynamic range amplifying structures such as the Doherty and others, and how well such approaches respond to different device technologies.
RF Waveform Engineering systems can also provide the necessary data for advanced transistor modelling approaches, and allow for example engineered RF load-lines that transit through specific points in the appropriate device model space at synchronised times. This project will consider such approaches in developing appropriate models for a range of device technologies, and how they respond to such linearisation techniques.
Proposed start date: 1st October 2013
The award will cover tuition fees at the Home/EU fee rate and will provide a stipend at the UK Research Council rate (£13,726 in 2013/14) plus an enhancement of £1,000 per annum. Please note that overseas candidates will be required to fund the balance of fees at the overseas fee rate themselves.
Number of Awards: 2
Academic Criteria: Candidates should have a first-class honours degree, or a 2.1 plus a postgraduate Masters degree (or their equivalents) in a relevant subject. Applicants whose first language is not English will be required to demonstrate proficiency in the English language (IELTS 6.5 or equivalent).
Residency: The studentship is open to Home, EU or overseas candidates.
How to Apply
In the first instance interested applicants are invited to send a CV and covering email/letter to Julie Cleaver (CleaverJ@Cardiff.ac.uk).
Please ensure that you quote the reference number of the project you wish to apply for in the email subject field:
- Non-linear Modelling From Non-linear Data (reference number: PRES6-PJT-2013)
- Baseband Linearisation Schemes for High Efficiency Power Amplifiers (reference number: PRES4-PJT-2013)
Shortlisted candidates will be invited to submit an online application form.
Application Deadline: 31st August 2013
For more information please contact Professor Paul Tasker by email (Tasker@Cardiff.ac.uk)