Solid-State Microwave Heating for Biomedical Applications A thesis submitted to the Cardiff University in candidature for the degree of Doctor of Philosophy By Azeem Imtiaz April 2015 Department of Electrical and Electronic Engineering, Cardiff University, United Kingdom Declaration This work has not previously been accepted in substance for any degree and is not concurrently submitted in candidature for any other higher degree. Signed:……………………………..(Candidate) Date:…………………………. Statement 1 This thesis is being submitted in partial fulfilment of the requirements for the degree of ……………..(insert as appropriate PhD, MPhil, EngD) Signed:……………………………..(Candidate) Date:…………………………. Statement 2 This thesis is the result of my own independent work/investigation, except where otherwise stated. Other sources are acknowledged by explicit references. Signed:……………………………..(Candidate) Date:…………………………. Statement 3 I hereby give consent for my thesis, if accepted, to be available for photocopying, inter-library loan and for the title and summary to be made available to outside organisations. Signed:……………………………..(Candidate) Date:…………………………. Copyright © 2015 Azeem Imtiaz Cardiff School of Engineering, Trevithick Building, 14-17 The Parade, Cardiff, South Glamorgan CF24 3AA United Kingdom. Abstract The research conducted in this thesis aims to develop an efficient microwave delivery system employing miniature resonant microwave cavities, targeted at compact, flexible and ideally field-deployable microwave-assisted diagnostic healthcare applications. The system comprises a power amplifier as a solid-state microwave source and a load - as a single mode cavity resonator to hold the sample. The compactness of the practical microwave delivery system relies on the direct integration of the sample-holding cavity resonator to the power amplifier and inclusion of the built-in directional coupler for power measurements. The solid state power transistors used in this research (10W-LDMOS, 10W-GaN) were provided by the sponsoring company NXP Inc. In practical microwave delivery applications, the impedance environment of the cavity resonators change significantly, and this thesis shows how this can be systematically utilized to present the optimal loading conditions to the transistor by simply designing the series delay lines. This load transfer technique, which critically can be achieved without employing bulky, lossy and physically larger output matching networks, allows high performance of the power amplifier to be achieved through waveform engineering at the intrinsic plane of the transistor. Starting with the impedance observation of a rectangular cavity, using only series delay lines allowed the practical demonstration of the high power and high efficiency fully integrated inverse class-F (F-1) power amplifier. Temperature is an important factor in a microwave heating and delivery system as it changes the impedance environment of the cavity resonator. This natural change in both cavity and sample temperature can be accommodated through simplified series matching lines and the microwave heating system capable of working over substantial bandwidth was again practically demonstrated. The inclusion of the coupler maintained the compactness of the system. In the practical situations envisaged, the microwave delivery system needs to accommodate natural variation between sample volumes and consistencies for heating. The experimental work considered the heating of different sample volumes i of water, and characterizing the change in the natural impedance environment of the cavity as a result. It was shown how the natural impedance variation can not only be accommodated, but also exploited, allowing ‘continuous’, high-efficiency performance to be achieved while processing a wide range of sample volumes. Specifically, using only transistor package parasitic, the impedance of the cavity itself together with a single series microstrip transmission line allows a continuous class-F-1 mode loading condition to be identified. Through different experiments, the microwave delivery systems with high- performance are demonstrated which are compact, flexible and efficient over operational bandwidth of the cavity resonators. ii Acknowledgements I begin by thanking Allah (the exalted) for blessing me with the excellent opportunity to pursue my doctoral research studies at Cardiff University in the supervision of the distinguished scientists. From the formative stages of this thesis to the final draft, I owe an immense debt of gratitude to my supervisor Dr. Jonathan Lees. I acknowledge that his sound advice, wisdom and commitment; kept my thesis on track during this time. Besides that, his insightful criticism and appreciation to my work was such an amazing blend that I found myself motivated throughout my studies. I am thankful to NXP, Nijmegen area, Netherlands for sponsoring my doctoral studies and I acknowledge the support of Dr. Klause Werner and Richard John Marlow for always expressing their interests and appreciation to my research work during conference meetings and informal telephone calls. Also I pay my sincere thankfulness to Dr. Aamir Sheikh and Dr. Akmal for many hours of academic discussions. I pay my sincere thankfulness to Professor Adrian Porch and for Professor Steve Cripps for always being very supportive and explaining me with difficult RF concepts in very simple words. During my work at school of engineering, I enjoyed the amazing company of my colleagues particularly Zulhazmi, David, Jerome and Jon who were always friendly and supportive. I’m grateful to everyone in the RF research group for several academic and nonacademic useful discussions throughout my studies. My special gratitude is for my family members particularly, my father and my brother Ijaz, who always helped me to improve the positive sides of myself. I’m lacking words to pay my sincere thankfulness to my wife Sara and my son Khalid who always stood beside me and supported me during difficult times. You both are simply great and I thank you for your ever green smiles. Cardiff, United Kingdom, April 2015 iii Dedicated to my parents, Mr. Muhammad Aslam & Mrs. Shehnaz Akhtar iv List of Publications First Author Papers 1 Azeem Imtiaz, Zulhazmi A.Mokhti, Jerome Cuenca and Jonathan Lees, “An Integrated Inverse-F power amplifier design approach for heating applications in a microwave resonant cavity” IEEE Asia Pacific Microwave Conference, pp.756-758, Nov 2014. 2 Azeem Imtiaz, Jon Hartley, Heungjae Choi and Jonathan Lees, “A High Power High Efficiency Integrated Solid-State Microwave Heating Structure for Portable Diagnostic Healthcare Applications”, IEEE-MTT-S IMWS-Bio Conference, pp.147-149, Dec 2014 3 Azeem Imtiaz, Jonathan Lees and Heungjae Choi, “An Integrated Continuous F-1 Mode Power Amplifier Design Approach for Microwave Enhanced Portable Health-Care Applications”, IEEE-MTT-S IMWS-Bio Mini Special Issue, no.1,vol.1, Apr 2015 US (Accepted –awaiting publication) Additional Papers 1 Hana Dobšíčěk Trefna, Azeem Imtiaz, Hoi-Shun Lui and Mikael Persson ,“Evolution of an UWB Antenna for Hyperthemia Array Applicator” 6th European Conference on Antennas and Propagation, pp.1046-1048, March 2012. v List of Terms RF Radio Frequency LDMOS Laterally diffused metal-oxide semiconductor GaN Gallium Nitride PA Power Amplifier E-Field Electric Field H-Field Magnetic Field ISM Industrial Scientific and Medical TE Transverse Electric TM Transverse Magnetic EM Electromagnetic CAD Computer Aided Design Q-Factor Quality Factor RLC Resistor-Inductor-Capacitor PAE Power Added Efficiency MAG Maximum Available Gain OMN Output Matching Network VDS Drain-Source Voltage VGS Gate-Source Voltage VKnee Knee Voltage CW Continuous Wave DUT Device Under Test VNA Vector Network Analyzer DAQ Data Acquisition IGEN-Plane Current Generator Plane DAC Data Access Component CF-1 Continuous F Inverse DNA Deoxyribonucleic Acid C-difficile Clostridium Difficile RT PCR Reverse Transcription-Polymerase Chain Reaction MAMEF Microwave-Accelerated Metal-Enhanced Fluorescence vi Contents CHAPTER.1 INTRODUCTION ....................................................................................................... 1 1.1 SOLID-STATE MICROWAVE HEATING ............................................................................................. 1 1.2 RESEARCH MOTIVATION ............................................................................................................. 3 1.3 THESIS OUTLINE ........................................................................................................................ 3 CHAPTER.2 LITERATURE REVIEW ............................................................................................... 5 2.1 MICROWAVE HEATING ............................................................................................................... 6 2.2 CONVENTIONAL MICROWAVE HEATING ......................................................................................... 7 2.3 SOLID-STATE MICROWAVE HEATING ........................................................................................... 13 2.4 POWER AMPLIFIER MODES OF OPERATION ................................................................................... 23 2.5 POWER AMPLIFIER DESIGN LIMITATIONS AND SOLUTIONS ............................................................... 31 2.6 BIOMEDICAL HEALTHCARE DIAGNOSTIC APPROACHES .................................................................... 35 2.7 CHAPTER SUMMARY................................................................................................................