Dr Jonathan Lees

Head of Department, Electrical & Electronic Engineering
Reader

School of Engineering

: leesj2@cardiff.ac.uk
: +44 (0)29 2087 4318
: C/4.07

: Available for postgraduate supervision

My key research areas are linear-efficient PA design and microwave characterisation with a specific interest in the design and optimisation of High-Efficiency Power Amplifiers. Significant achievements include the first published GaN Doherty amplifier, and more recently, activities considering the development of novel high-power, broad-band time-domain measurement and load-pull techniques that directly address the current and future needs of modern communication systems.

My most recent research activities include developement of compound semiconductors devices and circuits for high-frequency electronics, mm-wave characterisation, investigating RF properties of materials, microwave heating and disruption and application of microwave engineering to healthcare and diagnostics.

I began my career in 1998 developing optical and GPS-based positional tracking solutions with QinetiQ, U.K. and became a chartered Engineer in 1999. I obtained my MSc. and PhD. degrees from Cardiff University in 2002 and 2006 respectively and joined the Centre for High Frequency Engineering (CHFE) as a Research Associate in June 2005. I became a Lecturer in 2011 and then in 2016, a Senior Lecturer in Non-Linear Microwave Characterisation. Between 2009 and 2010, I was seconded to Mesuro as a Senior Hardware Engineer.

My current academic roles include Head of Department for Electrical and Electronic Engineering, as well as Year-4 MEng Tutor. Previous roles include Director of Taught Postgraduate programmes for Engineering, Year-1 Tutor for Integrated and Electrical and Electronic Engineering and Director for the Wireless and Microwave Communications Engineering MSc and its variants.

My research focus is developing non-linear microwave measurement and characterisation capabilities, high-performance microwave amplifiers, as well as the study of device non-linearity and linearization using modulated time-domain and envelope domain techniques. My work in this area culminated in the first published GaN Doherty amplifier, and more recent activities consider the development of novel high-power, broad-band time-domain measurement and load-pull techniques as well as dynamic supply modulation techniques in achieving high efficiency and high linearity in microwave power amplifiers. Over recent years I have applied my microwave expertise to medical and other applications, including the design of highly integrated microwave power amplifiers for diagnostic applications, and the generation and use of high power pulsed microwave energy for the detection of clostridium difficile.

I currently supervise / co-supervising over 10 PhD students in Microwave Engineering and related fields. I represented Cardiff University (founder member) in the European EUREKA OperaNET-2 programme driving down power consumption in mobile communications system networks.

Honours and awards

In June 2018 I was awarded the Cardiff University Business Innovation award for work with a local company developing low-power autonomous load-cells.

EEE Teacher of the Year award – EN3082/782 – 2016/17

2022

Sadeque, M. G., Yusoff, Z., Hashim, S. J., Marzuki, A. S. M., Lees, J. and FitzPatrick, D. 2022. Design of wideband continuous class-f power amplifier using low pass matching technique and harmonic tuning network. IEEE Access 10, pp. 92571-92582. (10.1109/ACCESS.2022.3202886)

2021

Prior-Jones, M. et al. 2021. Cryoegg: development and field trials of a wireless subglacial probe for deep, fast-moving ice. Journal of Glaciology 67(264), pp. 627-640. (10.1017/jog.2021.16)

2020

Chen, P., Quaglia, R., Lees, J., Merrick, B. M., Alt, A. and Tasker, P. J. 2020. Look-up table method for optimising coupling ratio in broadband sequential power amplifiers. IET Microwaves Antennas and Propagation 14(13), pp. 1626-1634. (10.1049/iet-map.2019.1102)
Chen, P., Quaglia, R., Lees, J., Merrick, B. M., Alt, A. and Tasker, P. 2020. Efficiency enhancement of a broadband sequential power amplifier using envelope tracking. Presented at: 2020 International Workshop on Integrated Nonlinear Microwave and Millimetre-Wave Circuits (INMMiC), Cardiff, Wales, 16-17 July 20202020 International Workshop on Integrated Nonlinear Microwave and Millimetre-Wave Circuits (INMMiC). IEEE pp. 1-3., (10.1109/INMMiC46721.2020.9160332)
Chen, P. et al. 2020. Optimising linearity of envelope tracking power amplifier using baseband linearisation approach. Presented at: 2020 International Workshop on Integrated Nonlinear Microwave and Millimetre-Wave Circuits (INMMiC), Cardiff, Wales, 16-17 July 20202020 International Workshop on Integrated Nonlinear Microwave and Millimetre-Wave Circuits (INMMiC). IEEE pp. 1-3., (10.1109/INMMiC46721.2020.9160347)
Bogusz, A., Lees, J., Quaglia, R., Watkins, G. T. and Cripps, S. 2020. Design and characterisation of an outphasing power amplifier with balun combiner. Presented at: 2019 IEEE MTT-S International Microwave Conference on Hardware and Systems for 5G and Beyond (IMC-5G), Altanta, GA, USA, 15-16 August 20192019 IEEE MTT-S International Microwave Conference on Hardware and Systems for 5G and Beyond (IMC-5G). IEEE pp. 1-3., (10.1109/IMC-5G47857.2019.9160351)
Alt, A., Villarruel-Parra, A., Chen, P., Alsahali, S., Forsyth, A., Tasker, P. J. and Lees, J. 2020. Characterising the baseband impedance of supply modulators using simple modulated signals. Presented at: 2020 International Workshop on Integrated Nonlinear Microwave and Millimetre-Wave Circuits (INMMiC), Cardiff, Wales, 16-17 July 20202020 International Workshop on Integrated Nonlinear Microwave and Millimetre-Wave Circuits (INMMiC). IEEE pp. 1-3., (10.1109/INMMiC46721.2020.9160186)
Chen, P., Alsahali, S., Alt, A., Wang, G., Casbon, M. A., Lees, J. and Tasker, P. J. 2020. Flexible bandwidth reduction technique for envelope tracking using low-pass finite impulse response filters. Electronics Letters 56(12), pp. 586-589. (10.1049/el.2020.0194)
Ahortor, E. K., Malyshev, D., Williams, C. F., Choi, H., Lees, J., Porch, A. and Baillie, L. 2020. The biological effect of 2.45 GHz microwaves on the viability and permeability of bacterial and yeast cells. Journal of Applied Physics 127(204902), pp. IMPORTED. (10.1063/1.5145009)
Prior-Jones, M. et al. 2020. Cryoegg: development and field trials of a wireless subglacial probe for deep, fast-moving ice. Presented at: EGU General Assembly 2020, Online, 4-8 May 2020. Copernicus {GmbH}, (10.5194/egusphere-egu2020-10204)
Alsahali, S. et al. 2020. Modulated rapid load pull system for the emulation of envelope tracking power amplifiers. Electronics Letters 56(7), pp. 325-328. (10.1049/el.2019.3896)
Eblabla, A., Alathbah, M., Wu, Z., Lees, J. and Elgaid, K. 2020. Membrane supported GaN CPW structures for high-frequency and high-power applications. Presented at: 2019 IEEE Asia-Pacific Microwave Conference (APMC), Marina Bay Sands, Singapore, 10-13 December 20192019 IEEE Asia-Pacific Microwave Conference (APMC). IEEE pp. 1179-1181., (10.1109/APMC46564.2019.9038731)

2019

Alsahali, S., Alt, A., Chen, P., Wang, G., Tasker, P. and Lees, J. 2019. Supply modulator ripple in envelope tracking systems - effects and countermeasures. Presented at: 49th European Microwave Conference (EuMC 2019), Paris, France, 01-03 October 20192019 49th European Microwave Conference (EuMC). IEEE pp. 710-713., (10.23919/EuMC.2019.8910890)
Chaudhary, M. A., Yusoff, Z., Lees, J., Benedikt, J. and Tasker, P. 2019. Auxiliary envelope tracking focused investigations of a 10W GaN HEMTs device. Presented at: 3rd International Conference on Circuits, Systems and Devices (ICCSD), Chengdu, China, 23-25 Aug 2017Proceedings of 3rd International Conference on Circuits, Systems and Devices (ICCSD). IEEE pp. 92., (10.1109/ICCSD.2019.8843202)
Bogusz, A., Lees, J., Quaglia, R., Watkins, G. and Cripps, S. 2019. Wideband compact planar balun for applications in outphasing and push-pull amplifiers. Electronics Letters 55(16), pp. 912-914. (10.1049/el.2018.7915)
Mokhti, Z. A., Lees, J., Cassan, C., Alt, A. and Tasker, P. J. 2019. The nonlinear drain-source capacitance effect on continuous-mode class-B/J power amplifiers. IEEE Transactions on Microwave Theory and Techniques 67(7), pp. 2741-2747. (10.1109/TMTT.2019.2918309)
Hamzah, H., Ahortor, E., Malyshev, D., Choi, H., Lees, J., Baillie, L. and Porch, A. 2019. A compact microwave applicator for the rapid detection of clostridium difficile. Presented at: 2019 IEEE MTT-S International Microwave Biomedical Conference (IMBioC), Nanjing, China, 6-8 May 20192019 IEEE MTT-S International Microwave Biomedical Conference (IMBioC). IEEE, (10.1109/IMBIOC.2019.8777882)
Alt, A. et al. 2019. Analysis of gain variation with changing supply voltages in GaN HEMTs for envelope tracking power amplifiers. IEEE Transactions on Microwave Theory and Techniques 67(7), pp. 2495-2504. (10.1109/TMTT.2019.2916404)
Alsahali, S. et al. 2019. A novel modulated rapid load pull system with digital pre-distortion capabilities. Presented at: 2019 93rd ARFTG Microwave Measurement Conference (ARFTG), Boston, MA, USA, 7 June 2019. , (10.1109/ARFTG.2019.8739220)
Eblabla, A., Li, X., Alathbah, M., Wu, Z., Lees, J. and Elgaid, K. 2019. Multi-channel AlGaN/GaN lateral schottky barrier diodes on low-resistivity silicon for sub-THz integrated circuits applications. IEEE Electron Device Letters 40(6), pp. 878-880. (10.1109/LED.2019.2912910)
Williams, C. F. et al. 2019. Bioluminescence of Vibrio fischeri: bacteria respond quickly and sensitively to pulsed microwave electric (but not magnetic) fields. Journal of Biomedical Optics 24(5), article number: 51412. (10.1117/1.JBO.24.5.051412)
Alt, A., Chen, P., Alsahali, S., Wang, G., Quaglia, R., Tasker, P. and Lees, J. 2019. Impact of the input impedance on the linearity of supply modulated GaN HEMT power amplifiers. Presented at: European Microwave Week 2019 (EuMW2019), 29 September - 03 October 2019.
Malyshev, D., Williams, C. F., Lees, J., Baillie, L. and Porch, A. 2019. Model of microwave effects on bacterial spores. Journal of Applied Physics 125(12), article number: 124701. (10.1063/1.5085442)
Alt, A., Quaglia, R., Chen, P., Alsahali, S., Tasker, P. and Lees, J. 2019. Class B* - A new high efficiency RF DC/DC converter concept using second harmonic generation/injection. Presented at: WPTC 2018: IEEE MTT-S Wireless Power Transfer Conference, Montreal, Quebec, 3-7 June 20182018 IEEE Wireless Power Transfer Conference (WPTC). IEEE, (10.1109/WPT.2018.8639317)
Quaglia, R. and Lees, J. 2019. Simplified analysis of the effect of load variation in common Doherty power amplifier architectures. Presented at: 2019 IEEE Topical Conference on RF/Microwave Power Amplifiers for Radio and Wireless Applications (PAWR), Orlando, FL, USA, 20-23 Jan 2019IEEE Topical Conference on RF/Microwave Power Amplifiers for Radio and Wireless Applications (PAWR). IEEE

2018

Alt, A., Quaglia, R., Chen, P., Alsahali, S., Tasker, P. J. and Lees, J. 2018. Analysis of highly efficient self-synchronous class-F microwave rectifiers using waveform engineering. Presented at: 48th European Microwave Conference (EuMC), Madrid, Spain, 23-27 Sep 2018Proceedings of the 48th European Microwave Conference. Piscataway, NJ: IEEE pp. 773-776., (10.23919/EuMC.2018.8541564)
Alt, A., Chen, P., Alsahali, S., Quaglia, R., Tasker, P. and Lees, J. 2018. Comparing FET technologies in terms of their suitability for broadband envelope tracking power amplifiers. Presented at: InMMIC, Brive La Gaillarde, 5-6 July 2018. pp. -.
Chen, P., Alsahali, S., Alt, A., Lees, J. and Tasker, P. J. 2018. Behavioral modeling of GaN power amplifiers using long short-term memory networks. Presented at: International Workshop on Integrated Nonlinear Microwave and Millimetre-wave Circuits (INMMIC), Brive La Gaillarde, France, 5-6 Jul 2018International Workshop on Integrated Nonlinear Microwave and Millimetre-wave Circuits (INMMIC). IEEE, (10.1109/INMMIC.2018.8429984)
Williams, C. et al. 2018. Real-time microscopic observation of biological interactions with microwave fields. Presented at: International Microwave Biomedical Conference (IMBioC), Philadelphia, USA, 14-15 Jun 2018International Microwave Biomedical Conference (IMBioC). IEEE pp. 199., (10.1109/IMBIOC.2018.8428902)
Chaudhary, M. A., Memon, Z. A., Yusoff, Z., Lees, J., Benedikt, J. and Tasker, P. 2018. Optimization of out-of-band impedance environment for linearity improvements of microwave power transistors. Presented at: 2018 5th International Conference on Electrical and Electronic Engineering (ICEEE), Istanbul, Turkey, 3-5 May 20182018 5th International Conference on Electrical and Electronic Engineering (ICEEE). IEEE pp. 219-223., (10.1109/ICEEE2.2018.8391334)
Hamzah, H., Lees, J. and Porch, A. 2018. Split ring resonator with optimised sensitivity for microfluidic sensing. Sensors and Actuators A: Physical 276, pp. 1-10. (10.1016/j.sna.2018.03.023)
Hamzah, H., Abduljabar, A., Lees, J. and Porch, A. 2018. A compact microwave microfluidic sensor using a re-entrant cavity. Sensors 18(3), article number: 910. (10.3390/s18030910)
Chaudhary, M. A., Memon, Z. A., Lees, J., Benedikt, J. and Tasker, P. 2018. Multitone measurement system for linearity investigations of microwave devices. Presented at: International Multi-Topic Conference (Inmic), Lahore, Pakistan, 24-26 Nov 2017International Multi-Topic Conference (Inmic). IEEE, (10.1109/INMIC.2017.8289455)
Bogusz, A., Costello, Z., Quaglia, R., Bell, J., Lees, J., Tasker, P. and Cripps, S. 2018. Power and efficiency continuous modes in saturated GaN HEMT devices. Presented at: Inmmic 2018, Brive-La-Gaillarde, France, 5- 6 July 2018.

2017

Alt, A. and Lees, J. 2017. Improving efficiency, linearity and linearisability of an asymmetric doherty power amplifier by modulating the peaking amplifier’s supply voltage. Presented at: 20th EuMW 2017, Nuremberg, Germany, 8-13 October 20172017 47th European Microwave Conference (EuMC). IEEE pp. 464-467., (10.23919/EuMC.2017.8230890)
Hefford, S., Parker, N., Lees, J. and Porch, A. 2017. Monitoring changes in microwave asorption of Ti64 powder during microwave sintering. Presented at: 2017 47th European Microwave Conference (EuMC), Nuremberg, Germany, 10-12 October 20172017 47th European Microwave Conference (EuMC). IEEE pp. 927-929., (10.23919/EuMC.2017.8230997)
Zhou, H., Pal, A., Mehta, A., Nagasundaram, E., Lees, J. and Mirshekar-Syahkal, D. 2017. Power amplifier and antenna integration utilizing capacitively coupled feeding mechanism. Presented at: International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting, San Diego, CA, USA, 9-14 July 20172017 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting. IEEE pp. 2355-2356., (10.1109/APUSNCURSINRSM.2017.8073220)
Abduljabar, A. A., Clark, N., Lees, J. and Porch, A. 2017. Dual mode microwave microfluidic sensor for temperature variant liquid characterization. IEEE Transactions on Microwave Theory and Techniques 65(7), pp. 2572 - 2582. (10.1109/TMTT.2016.2647249)
Pal, A., Zhou, H., Mehta, A., Nagasundaram, E., Lees, J. and Mirshekar-Syahkal, D. 2017. Co-design of an antenna-power amplifier RF front-end block without matching network for 2.4 GHz WiFi application. Presented at: 2017 IEEE Radio and Wireless Symposium (RWS), Phoenix, AZ, USA, 15-18 January 20172017 IEEE Radio and Wireless Symposium (RWS). IEEE pp. 201-203., (10.1109/RWS.2017.7885987)
Dong, S., Lees, J. and Tasker, P. J. 2017. A de-embedding network at higher frequency and its error analysis. Presented at: IEEE International Conference on Electronic Information and Communication Technology (ICEICT), Harbin, China, 20-22 Aug 2016IEEE International Conference on Electronic Information and Communication Technology (ICEICT). IEEE pp. 512-514., (10.1109/ICEICT.2016.7879754)
Chaudhary, M. A., Memon, Z. A., Yusoff, Z., Lees, J., Benedikt, J. and Tasker, P. J. 2017. Characterization of baseband electrical memory in microwave devices using multi-tone measurement system. Presented at: 2016 16th Mediterranean Microwave Symposium (MMS), 14-16 November 201616th Mediterranean Microwave Symposium (MMS), 2016. IEEE pp. 1., (10.1109/MMS.2016.7803811)

2016

Dong, S., Tasker, P. J., Wang, G. and Lees, J. 2016. A practicable de-embedding network at higher frequency of a packaged GaN device. Presented at: 2016 IEEE MTT-S International Wireless Symposium (IWS), 14-16 March 2016IEEE MTT-S International Wireless Symposium (IWS), 2016. IEEE pp. 1., (10.1109/IEEE-IWS.2016.7585473)
Yusoff, Z., Annuar, F. M., Kung, F., Hashim, S. J., Lees, J. and Cripps, S. C. 2016. The effect of tracking generator efficiency to overall RF power amplifier system efficiency. Presented at: 2016 IEEE International Conference on Semiconductor Electronics (ICSE), 17-19 August 20162016 IEEE International Conference on Semiconductor Electronics (ICSE). IEEE pp. 344-347., (10.1109/SMELEC.2016.7573662)
Williams, C. F. et al. 2016. What the deep sea can tell us about microwaves. Presented at: International Microwave Symposium IMS, San Francisco, California, 22-27 May 2016Microwave Symposium (IMS), 2016 IEEE MTT-S International. IEEE, (10.1109/MWSYM.2016.7540432)
Williams, C. F., Geroni, G. M., Pirog, A., Lloyd, D., Lees, J. and Porch, A. 2016. The separated electric and magnetic field responses of luminescent bacteria exposed to pulsed microwave irradiation. Applied Physics Letters 109(9), article number: 93701. (10.1063/1.4961970)
Chaudhary, M. A., Lees, J., Benedikt, J. and Tasker, P. J. 2016. Modulated waveform measurement and engineering system. Presented at: 2015 2nd International Conference on Electronics and Communication Systems (ICECS), Cairo, Egypt, 6-9 December 20152015 IEEE International Conference on Electronics, Circuits, and Systems (ICECS 2015). Institute of Electrical and Electronics Engineers (IEEE) pp. 252-255., (10.1109/ICECS.2015.7440296)
Yusoff, Z., Lees, J., Chaudhary, M. A. and Cripps, S. C. 2016. Ferrite toroidal core with a trifilar wound RF broadband transformer design for tracking generators in wideband code division multiple access envelope tracking RFPA systems. Journal of Electromagnetic Waves and Applications 30(5), pp. 599-611. (10.1080/09205071.2016.1138899)

2015

Imtiaz, A., Lees, J., Choi, H. and Joshi, L. T. 2015. An integrated continuous class-F-1 mode power amplifier design approach for microwave enhanced portable diagnostic applications. IEEE Transactions on Microwave Theory and Techniques 63(10), pp. 3007-3015. (10.1109/TMTT.2015.2472417)
Brazzini, T. et al. 2015. Study of hot electrons in AlGaN/GaN HEMTs under RF Class B and Class J operation using electroluminescence. Microelectronics Reliability 55(12), pp. 2493-2498. (10.1016/j.microrel.2015.09.023)
Mokhti, Z. A., Lees, J., Tasker, P. J. and Cassan, C. 2015. Investigating the linearity versus efficiency trade-off of different power amplifier modes in an envelope tracking architecture. 2015 10th European microwave integrated circuits conference (eumic), pp. 357-360. (10.1109/EuMIC.2015.7345143)
Brazzini, T. et al. 2015. Electroluminescence of hot electrons in AlGaN/GaN high-electron-mobility transistors under radio frequency operation. Applied Physics Letters 106(21), article number: 213502. (10.1063/1.4921848)
Imtiaz, A., Hartley, J., Choi, H. and Lees, J. 2015. A high power high efficiency integrated solid-state microwave heating structure for portable diagnostic healthcare applications. Presented at: IEEE MTT-S 2014 IEEE International Microwave Workshop Series on RF and Wireless Technologies for Biomedical and Healthcare Applications, London, 8-10 December 20142014 IEEE MTT-S international microwave workshop series on RF and wireless technologies for biomedical and healthcare applications (IMWS-Bio). IEEE pp. 1-3., (10.1109/IMWS-BIO.2014.7032437)

2014

Hartley, J., Lees, J., Cuenca, J. and Choi, H. 2014. Assessment of machine oil quality by microwave cavity perturbation method. Presented at: 2014 International Symposium on Information Technology Convergence (ISITC 2014), Jeonju, Republic of Korea, 30-31 October 2014.
Koh, M., Bell, J. J., Williams, D., Patterson, A., Lees, J., Root, D. E. and Tasker, P. J. 2014. Frequency scalable large signal transistor behavioral model based on admittance domain formulation. Presented at: International Microwave Symposium, Tampa, Florida, 1-6 June 20142014 IEEE MTT-S International Microwave Symposium (IMS). Picastaway, NJ: IEEE pp. 1-3., (10.1109/MWSYM.2014.6848287)
A Mokhti, Z. B., Tasker, P. J. and Lees, J. 2014. Correlation analysis between a VNA-based passive load pull system and an oscilloscope-based active load pull system: a case study. Presented at: 83rd ARFTG Microwave Measurement Conference 2014, Tampa, USA, 6 June 201483rd ARFTG Microwave Measurement Conference (ARFTG), 2014. pp. 1-4., (10.1109/ARFTG.2014.6899535)
Ogboi, F. L. et al. 2014. Investigation of various envelope complexity linearity under modulated stimulus using a new envelope formulation approach. Presented at: 83rd ARFTG Microwave Measurement Conference 2014, Tampa, USA, 1 - 6 June 2014Compound Semiconductor Integrated Circuit Symposium (CSICs), 2014 IEEE. IEEE pp. 1-4., (10.1109/CSICS.2014.6978563)
Yang, F., Lees, J., Choi, H., Yu, H. and Tasker, P. J. 2014. Continuous class BJ power amplifier with DGS output matching. Presented at: 83rd ARFTG Microwave Measurement Conference 2014, Tampa, USA, 6 June 2014Microwave Symposium (IMS), 2014 IEEE MTT-S International. IEEE pp. 1-4., (10.1109/MWSYM.2014.6848562)
A Mokhti, Z. B., Tasker, P. J. and Lees, J. 2014. Using waveform engineering to optimize class-F power amplifier performance in an envelope tracking architecture. Presented at: 44th European Microwave Conference (EuMC) 2014, Rome, Italy, 6-9 October 201444th European Microwave Conference (EuMC 2014). IEEE pp. 1301-1304., (10.1109/EuMC.2014.6986682)
Aldoumani, A., Williams, T., Lees, J. and Tasker, P. J. 2014. Enhanced vector calibration of load-pull measurement systems. Presented at: 83rd ARFTG Microwave Measurement Conference 2014, Tampa, FL, USA, 6 June 2014ARFTG Microwave Measurement Conference (ARFTG), 2014 83rd. IEEE pp. 1-4., (10.1109/ARFTG.2014.6899508)
Ogboi, F. L. et al. 2014. High bandwidth investigations of a baseband linearization approach formulated in the envelope domain under modulated stimulus. Presented at: European Microwave Conference (EuMC) 2014, Rome, Italy, 6-9 October 2014European Microwave Conference (EuMC), Vol. 44. IEEE pp. 1305-1308., (10.1109/EuMC.2014.6986683)
Mokhti, Z. A., Tasker, P. J. and Lees, J. 2014. Using waveform engineering to optimize Class-F power amplifier performance in an envelope tracking architecture. Presented at: 9th European Microwave Integrated Circuit Conference (EuMIC), Rome, Italy, 6-7 Octpber 2014European Microwave Integrated Circuit Conference (EuMIC), 2014 9th. IEEE pp. 357-360., (10.1109/EuMIC.2014.6997866)
Mokhti, Z. A., Tasker, P. J. and Lees, J. 2014. Analyzing the improvement in efficiency through the integration of class-F power amplifiers compared to class-AB in an envelope tracking architecture. Presented at: 26th International Teletraffic Congress (ITC), Karlskrona, Sweden, 9-11 September 2014Teletraffic Congress (ITC), 2014 26th International. pp. 1-4., (10.1109/ITC.2014.6932967)
Ogboi, F. L. et al. 2014. Sensitivity of AM/AM linearizer to AM/PM distortion in devices. Presented at: 83rd ARFTG Microwave Measurement Conference 2014, Tampa, FL, USA, 6 June 2014ARFTG Microwave Measurement Conference (ARFTG), 2014 83rd. IEEE pp. 1-4., (10.1109/ARFTG.2014.6899507)

2013

Kural, A., Pullin, R., Holford, K. M., Lees, J., Naylon, A. J., Paget, C. and Featherston, C. A. 2013. Design and characterization of an ultrasonic lamb-wave power delivery system. IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control 60(6), pp. 1134-1140. (10.1109/TUFFC.2013.2676)
Morgan, A. J. et al. 2013. Efficient microwave heating of microfluidic systems. Sensors and Actuators B: Chemical 181, pp. 904-909. (10.1016/j.snb.2013.02.099)
Schmid, U. et al. 2013. Hybrid energy storage system for wireless sensor node powered by aircraft specific thermoelectric energy harvesting. Presented at: Smart Sensors, Actuators, and MEMS VI, Grenoble, France, 24 April 2013Proc. SPIE 8763, Smart Sensors, Actuators, and MEMS VI, Vol. 8763. SPIE pp. 876307., (10.1117/12.2017691)
Featherston, C., Holford, K. M., Pullin, R., Lees, J., Eaton, M. J. and Pearson, M. R. 2013. An autonomous structural health monitoring solution. Presented at: Microtechnologies 2013, Grenoble, France, 24-26 April 2013Proc. SPIE 8763, Smart Sensors, Actuators, and MEMS VI. Society of Photo-Optical Instrumentation Engineers (SPIE) pp. 876302., (10.1117/12.2018401)
Yusoff, Z., Lees, J., Chaudhary, M. A., Carrubba, V., Choi, H., Tasker, P. J. and Cripps, S. C. 2013. Simple and low-cost tracking generator design in envelope tracking radio frequency power amplifier system for WCDMA applications. IET Microwaves, Antennas & Propagation 7(10), pp. 802-808. (10.1049/iet-map.2013.0091)
Thangaraj, K., Elefsiniots, A., Becker, T., Schmid, U., Lees, J., Featherston, C. A. and Pullin, R. 2013. Energy storage options for wireless sensors powered by aircraft specific thermoelectric energy harvester. Microsystem Technologies 20(4-5), pp. 701-707. (10.1007/s00542-013-2009-3)
Koh, M., Bell, J. J., Williams, D., Patterson, A., Wohlmuth, W., Lees, J. and Tasker, P. J. 2013. X-band MMIC scalable large signal model based on unit cell behavioral data model and passive embedding network. Presented at: International Microwave Symposium, Seattle, WA, 2-7 June 20132013 IEEE MTT-S International Microwave Symposium Digest (IMS). Picastaway, NJ: IEEE pp. 1-4., (10.1109/MWSYM.2013.6697424)
Aldoumani, A., Tasker, P. J., Saini, R. S., Bell, J. J., Williams, T. and Lees, J. 2013. Operation and calibration of VNA-based large signal RF I-V waveform measurements system without using a harmonic phase reference standard. Presented at: ARFTG Microwave Measurement Conference (ARFTG), Seattle, WA, 7-7 June 20132013 81st ARFTG Microwave Measurement Conference (ARFTG). Picastaway, NJ: IEEE pp. 1-4., (10.1109/ARFTG.2013.6579055)
Ogboi, F. L. et al. 2013. A LSNA configured to perform baseband engineering for device linearity investigations under modulated excitations. Presented at: 43rd European Microwave Conference, Nuremberg, Germany, 7-10 October 2013Proceedings of the 43rd European Microwave Conference. pp. 684-687.
Chaudhary, M. A., Memon, Z. A., Lees, J., Benedikt, J. and Tasker, P. J. 2013. Investigation of baseband electrical memory effects on the dynamic characteristics of power transistors. Presented at: 2013 16th International Multi Topic Conference (INMIC), Lahore, Pakistan, 19-20 December 2013Multi Topic Conference (INMIC), 2013 16th International. IEEE pp. 106-109., (10.1109/INMIC.2013.6731333)
Chaudhary, M. A., Lees, J., Benedikt, J. and Tasker, P. J. 2013. Reduction of baseband electrical memory effects using broadband active baseband load-pull. Presented at: 2013 IEEE International Wireless Symposium (IWS), Beijing, China, 14-18 April 2013Wireless Symposium (IWS), 2013 IEEE International. IEEE pp. 1-4., (10.1109/IEEE-IWS.2013.6616709)
Hone, T. M. et al. 2013. Inverse active load-pull in an inverse Doherty amplifier. Presented at: 2013 IEEE Topical Conference on Power Amplifiers for Wireless and Radio Applications, Santa Clara, CA, USA, 20 Jauary 2013Power Amplifiers for Wireless and Radio Applications (PAWR), 2013 IEEE Topical Conference on. IEEE pp. 4-6., (10.1109/PAWR.2013.6490170)
Pearson, M., Lees, J., Featherston, C. and Pullin, R. 2013. 9th international conference on advances in experimental mechanics. Presented at: 9th International Conference on Advances in Experimental Mechanics, Cardiff, Wales, 3 - 5 September 2013.

2012

Bensmida, S. et al. 2012. Nonlinear envelope tracking for efficiency optimization of power amplifiers. Presented at: 7th European Microwave Integrated Circuits Conference (EuMIC) 2012, Amsterdam, The Netherlands, 29-30 October 20127th European Microwave Integrated Circuits Conference (EuMIC), 2012. Picastaway, NJ: IEEE pp. 480-483.
Carrubba, V., Akmal, M., Quay, R., Lees, J., Benedikt, J., Cripps, S. C. and Tasker, P. J. 2012. The Continuous Inverse Class-F Mode With Resistive Second-Harmonic Impedance. IEEE Transactions on Microwave Theory and Techniques 60(6), pp. 1928-1936. (10.1109/TMTT.2012.2189228)
Hone, T. M. et al. 2012. Controlling Active Load-Pull in a Dual-Input Inverse Load Modulated Doherty Architecture. IEEE Transactions on Microwave Theory and Techniques 60(6), pp. 1797-1804. (10.1109/TMTT.2012.2190748)
McGenn, W., Choi, H., Lees, J., Uren, M. J., Benedikt, J. and Tasker, P. J. 2012. Development of a RF waveform stress test procedure for GaN HFETs subjected to infinite VSWR sweeps. Presented at: 2012 IEEE MTT-S International Microwave Symposium Digest, Montreal, Canada, 17-22 June 2012Microwave Symposium Digest (MTT), 2012 IEEE MTT-S International. IEEE pp. 1-3., (10.1109/MWSYM.2012.6259725)
Carrubba, V. et al. 2012. Continuous-ClassF3 power amplifier mode varying simultaneously first 3 harmonic impedances. Presented at: 2012 IEEE MTT-S International Microwave Symposium Digest, Montreal, Canada, 17-22 June 2012Microwave Symposium Digest (MTT), 2012 IEEE MTT-S International. IEEE pp. 1-3., (10.1109/MWSYM.2012.6258343)
Smith, R. M., Lees, J., Tasker, P. J., Benedikt, J. and Cripps, S. C. 2012. A 40W push-pull power amplifier for high efficiency, decade bandwidth applications at microwave frequencies. Presented at: 2012 IEEE MTT-S International Microwave Symposium Digest (MTT, Montreal, Canada, 17-22 June 2012Microwave Symposium Digest (MTT), 2012 IEEE MTT-S International. IEEE pp. 1-3., (10.1109/MWSYM.2012.6259418)
Smith, R. M., Lees, J., Tasker, P. J., Benedikt, J. and Cripps, S. C. 2012. A Novel Formulation for High Efficiency Modes in Push-Pull Power Amplifiers Using Transmission Line Baluns. IEEE Microwave and Wireless Components Letters 22(5), pp. 257-259. (10.1109/LMWC.2012.2191273)
Pullin, R. et al. 2012. On the Development of a Damage Detection System using Macro-fibre Composite Sensors. Journal of Physics. Conference Series 382(1), article number: 12049. (10.1088/1742-6596/382/1/012049)
Tasker, P. J., Carrubba, V., Wright, P., Lees, J., Benedikt, J. and Cripps, S. C. 2012. Wideband PA design: The "continuous" mode of operation. Presented at: Compound Semiconductor Integrated Circuit Symposium (CSICS), La Jolla, CA, USA, 14-17 October 2012Compound Semiconductor Integrated Circuit Symposium (CSICS), 2012 IEEE. IEEE pp. 1-4., (10.1109/CSICS.2012.6340048)
Mimis, K., Morris, K. A., Beach, M. A., McGeehan, J. P., Lees, J., Benedikt, J. and Tasker, P. J. 2012. Overlapped segment piece-wise polynomial pre-distortion for the linearisation of power amplifiers in the presence of high PAPR OFDM signals. Presented at: 2012 IEEE MTT-S International Microwave Symposium Digest, Montreal, Canada, 17-22 June 2012Microwave Symposium Digest (MTT), 2012 IEEE MTT-S International. pp. 1-3., (10.1109/MWSYM.2012.6259543)
Akmal, M., Carrubba, V., Lees, J., Benedikt, J. and Tasker, P. J. 2012. An enhanced modulated waveform measurement system. Australian Journal of Electrical and Electronics Engineering 9(4), pp. 429-438. (10.7158/E11-033.2012.9.4)
Arnold, M., Featherston, C. A., Pearson, M. R., Lees, J. and Kural, A. 2012. Energy management systems for energy harvesting in structural health monitoring applications. Key Engineering Materials 518, pp. 137-153. (10.4028/www.scientific.net/KEM.518.137)
Akmal, M. et al. 2012. Characterization of electrical memory effects for complex multi-tone excitations using broadband active baseband load-pull. Presented at: 7th European Microwave Integrated Circuits Conference, Amsterdam, The Netherlands, 29-30 October 20127th European Microwave Integrated Circuits Conference (EuMIC), 2012. Picastaway, NJ: IEEE pp. 885-888.

2011

Carrubba, V., Clarke, A. L., Akmal, M., Lees, J., Benedikt, J., Tasker, P. J. and Cripps, S. C. 2011. On the extension of the continuous class-F mode power amplifier. IEEE Transactions on Microwave Theory and Techniques 59(5), pp. 1294-1303. (10.1109/TMTT.2011.2117435)
Yusoff, Z. B., Akmal, M., Carrubba, V., Lees, J., Benedikt, J., Tasker, P. J. and Cripps, S. C. 2011. The benefit of GaN characteristics over LDMOS for linearity improvement using drain modulation in power amplifier system. Presented at: 2011 Workshop on Integrated Nonlinear Microwave and Millimetre-Wave Circuits, Vienna, Austria, 18-19 April 20112011 Workshop on Integrated Nonlinear Microwave and Millimetre-Wave Circuits (INMMIC 2011). New York: IEEE pp. 109-112., (10.1109/INMMIC.2011.5773334)
Carrubba, V., Lees, J., Benedikt, J., Tasker, P. J. and Cripps, S. C. 2011. A novel highly efficient broadband continuous class-F RFPA delivering 74% average efficiency for an octave bandwidth. Presented at: 2011 IEEE/MTT-S International Microwave Symposium, Baltimore, MD, USA, 5-10 June 20112011 IEEE/MTT-S International Microwave Symposium - MTT 2011. New York: IEEE pp. 350-353., (10.1109/MWSYM.2011.5972701)
Yusoff, Z. B., Lees, J., Benedikt, J., Tasker, P. J. and Cripps, S. C. 2011. Linearity improvement in RF power amplifier system using integrated Auxiliary Envelope Tracking system. Presented at: 2011 IEEE/MTT-S International Microwave Symposium, Baltimore, MD, USA, 5-10 June 2011 Presented at Seigel, P. et al. eds.2011 IEEE/MTT-S International Microwave Symposium - MTT 2011. New York: IEEE pp. 1752-1755., (10.1109/MWSYM.2011.5972769)
FitzPatrick, D., Saini, R., Lees, J., Benedikt, J., Cripps, S. C. and Tasker, P. J. 2011. A waveform engineering approach to the design of improved efficiency wideband MMIC amplifiers. Presented at: Wireless and Microwave Technology Conference (WAMICON), 2011 IEEE 12th Annual., Clearwater Beach, FL, USA, 18-19 April 20112011 IEEE 12th Annual Wireless and Microwave Technology Conference (WAMICON), Clearwater Beach, FL, 18-19 April 2011. Los Alamitos, CA: IEEE pp. 225-230., (10.1109/WAMICON.2011.5872859)
Akmal, M. et al. 2011. Linearity enhancement of GaN HEMTs under complex modulated excitation by optimizing the baseband impedance environment. Presented at: 2011 IEEE/MTT-S International Microwave Symposium, Baltimore, MD, USA, 5-10 June 2011 Presented at Seigel, P. et al. eds.2011 IEEE/MTT-S International Microwave Symposium - MTT 2011. New York: IEEE pp. 1747-1750., (10.1109/MWSYM.2011.5972833)
Smith, R. M., Cripps, S. C., Tasker, P. J., Benedikt, J. and Lees, J. 2011. A design methodology for the realization of multi-decade baluns at microwave frequencies. Presented at: 2011 IEEE/MTT-S International Microwave Symposium, Baltimore, MD, USA, 5-10 June 2011 Presented at Seigel, P. et al. eds.2011 IEEE/MTT-S International Microwave Symposium - MTT 2011. New York: IEEE pp. 1204-1208., (10.1109/MWSYM.2011.5972702)
Bell, J. J., Saini, R., Woodington, S. P., Lees, J., Benedikt, J., Cripps, S. C. and Tasker, P. J. 2011. Behavioral model analysis using simultaneous active fundamental load-pull and harmonic source-pull measurements at X-band. Presented at: 2011 IEEE/MTT-S International Microwave Symposium, Baltimore, MD, USA, 5-10 June 2011Microwave Symposium Digest (MTT), 2011 IEEE MTT-S International. New York: IEEE pp. 982-986., (10.1109/MWSYM.2011.5972803)
Saini, R. et al. 2011. High speed non-linear device characterization and uniformity investigations at X-band frequencies exploiting behavioral models. Presented at: 2011 77th ARFTG Microwave Measurement Conference (ARFTG), Baltimore, MD, USA, 10 June 2011Design and Measurement of Microwave Systems - Proceedings of the 2011 77th ARFTG Microwave Measurement Conference (ARFTG). Los Alamitos, CA: IEEE, (10.1109/ARFTG77.2011.6034552)
Carrubba, V. et al. 2011. High-speed device characterization using an active load-pull system and waveform engineering postulator. Presented at: 2011 77th ARFTG Microwave Measurement Conference (ARFTG), Baltimore, MD, USA, 10 June 2011Design and Measurement of Microwave Systems - Proceedings of the 2011 77th ARFTG Microwave Measurement Conference (ARFTG). Los Alamitos, CA: IEEE, (10.1109/ARFTG77.2011.6034553)
Canning, T. A. J., Almuhaisen, A., Lees, J., Benedikt, J., Cripps, S. C. and Tasker, P. J. 2011. Utilization of RF I-V waveform load-pull information to identify the role FET knee profile has on locating the efficiency maxima. Presented at: 2011 78th ARFTG Microwave Measurement Symposium (ARFTG), Tempe, AZ, USA, 1-2 December 2011Proceedings of the 2011 78th ARFTG Microwave Measurement Symposium (ARFTG) - High Power RF Measurement Techniques. Los Alamitos, CA: IEEE, (10.1109/ARFTG78.2011.6183864)
Saini, R., Bell, J. J., Williams, T., Lees, J., Benedikt, J. and Tasker, P. J. 2011. Interpolation and extrapolation capabilities of non-linear behavioural models. Presented at: 2011 78th ARFTG Microwave Measurement Symposium (ARFTG), Tempe, AZ, USA, 1-2 December 2011Proceedings of the 2011 78th ARFTG Microwave Measurement Symposium (ARFTG) - High Power RF Measurement Techniques. Los Alamitos, CA: IEEE, (10.1109/ARFTG78.2011.6183865)
Carrubba, V. et al. 2011. Exploring the Design Space for Broadband PAs using the Novel "Continuous Inverse Class-F Mode". Presented at: 6th European Microwave Integrated Circuits Conference (EuMIC) 2011, Manchester, UK, 10-11 October 2011Proceedings of the 41st European Microwave Conference (EuMC). IEEE pp. 333-336.
Hone, T. et al. 2011. Optimized load modulation in a doherty amplifier using a current injection technique. Presented at: 6th European Microwave Integrated Circuits Conference (EuMIC) 2011, Manchester, UK, 10-11 October 2011Proceedings of the 6th European Microwave Integrated Circuits Conference (EuMIC). Los Alamitos, CA: IEEE pp. 296-299.
Akmal, M. et al. 2011. An enhanced modulated waveform measurement system for the robust characterization of microwave devices under modulated excitation. Presented at: Microwave Integrated Circuits Conference (EuMIC), 2011 European, Manchester, 10-11 October 2011Microwave Integrated Circuits Conference (EuMIC), 2011 European. IEEE pp. 180-183.
Paynter, M. et al. 2011. Non-linear large signal PA modelling for switching-mode operation (class-F/continuous class-F). Presented at: 6th European Microwave Integrated Circuits Conference (EuMIC) 2011, Manchester, UK, 10-11 October 2011Proceedings of the 6th European Microwave Integrated Circuits Conference (EuMIC). Los Alamitos, CA: IEEE pp. 152-155.
Almuhaisen, A., Lees, J., Cripps, S. C., Tasker, P. J. and Benedikt, J. 2011. Wide band high-efficiency power amplifier design. Presented at: 6th European Microwave Integrated Circuits Conference (EuMIC) 2011, Manchester, UK, 10-11 October 2011Proceedings of the 6th European Microwave Integrated Circuits Conference (EuMIC). Los Alamitos, CA: IEEE pp. 184-187.

2010

Hashmi, M. S., Clarke, A. L., Lees, J., Helaoui, M., Tasker, P. J. and Ghannouchi, F. M. 2010. Agile harmonic envelope load-pull system enabling reliable and rapid device characterization. Measurement Science and Technology 21(5), article number: 55109. (10.1088/0957-0233/21/5/055109)
Hashmi, M. S., Clarke, A. L., Woodington, S. P., Lees, J., Benedikt, J. and Tasker, P. J. 2010. An accurate calibrate-able multiharmonic active load-pull system based on the envelope load-pull concept. IEEE Transactions on Microwave Theory and Techniques 58(3), pp. 656-664. (10.1109/TMTT.2010.2040403)
Clarke, A. L., Akmal, M., Lees, J., Tasker, P. J. and Benedikt, J. 2010. Investigation and analysis into device optimization for attaining efficiencies in-excess of 90% when accounting for higher harmonics. Presented at: IEEE MTT-S International Microwave Symposium, Anaheim, CA, USA, 23-28 May 20102010 IEEE MTT-S International Microwave Symposium Digest (MTT 2010). New York: IEEE pp. 1114-1117., (10.1109/MWSYM.2010.5517222)
Akmal, M. et al. 2010. The effect of baseband impedance termination on the linearity of GaN HEMTs. Presented at: European Microwave Conference 2010, Paris, France. Vol. 561636. pp. 1046-1049.
Akmal, M. et al. 2010. The impact of baseband electrical memory effects on the dynamic transfer characteristics of microwave power transistors. Presented at: 2010 Workshop on Integrated Nonlinear Microwave and Millimetre-Wave Circuits (INMMIC), Gothenburg, Sweden. Vol. 548011. pp. 148-151.
Woodington, S. P., Saini, R., Williams, D., Lees, J., Benedikt, J. and Tasker, P. J. 2010. Behavioral model analysis of active harmonic load-pull measurements. Presented at: IEEE MTT-S International Microwave Symposium, Anaheim, CA, USA, 23-28 May 2010Microwave Symposium Digest (MTT), 2010 IEEE MTT-S International. New York: IEEE pp. 1688-1691., (10.1109/MWSYM.2010.5517261)
Almuhaisen, A., Wright, P. T., Lees, J., Tasker, P. J., Cripps, S. C. and Benedikt, J. 2010. Novel wide band high-efficiency active harmonic injection power amplifier concept. Presented at: IEEE MTT-S International Microwave Symposium, Anaheim, CA, USA, 23-28 May 20102010 IEEE MTT-S International Microwave Symposium Digest (MTT 2010). New York: IEEE pp. 664-667., (10.1109/MWSYM.2010.5514759)
FitzPatrick, D. M., Williams, T., Lees, J., Benedikt, J., Cripps, S. C. and Tasker, P. 2010. Exploitation of active load-pull and DLUT models in MMIC design. Presented at: IEEE Radio Frequency Integrated Circuits Symposium, Anaheim, CA, USA, 23-25 May 2010Proceedings of the 2010 IEEE Radio Frequency Integrated Circuits Symposium May 23-25, 2010, Anaheim, California, USA. Piscataway, NJ: IEEE pp. 487-490., (10.1109/RFIC.2010.5477406)
Naylon, A. J. et al. 2010. Efficient Microwave heating and dielectric characterization of microfluidic systems. Presented at: Proceedings of MicroTAS 2010, Groningen, The Netherlands. pp. 2092-2094.
Bensmida, S. et al. 2010. Generic pre-distortion of a Class-J Power amplifier. Presented at: European Microwave Conference 2010, Paris, France. Vol. 561648. pp. 1022-1025.
Carrubba, V., Clarke, A. L., Akmal, M., Lees, J., Benedikt, J., Tasker, P. and Cripps, S. C. 2010. The continuous Class-F Mode mode power amplifier. Presented at: European Microwave Conference (EuMC) 2010, Paris, France. Vol. 561630. pp. 1674-1677.
Lees, J. et al. 2010. Waveform engineering applied to linear-efficient PA design. Presented at: 2010 IEEE 11th Annual Wireless and Microwave Technology Conference (WAMICON 2010), Melbourne Beach, USA, 12-13 April, 2010. Vol. 546184., (10.1109/WAMICON.2010.5461847)
Saini, R., Woodington, S. P., Lees, J., Benedikt, J. and Tasker, P. J. 2010. An intelligence driven active loadpull system. Presented at: 75th ARFTG Microwave Measurement Conference: Measurement of Modulated Signals for Communications, Anaheim, USA. Vol. 549632.
Akmal, M. et al. 2010. Minimization of baseband electrical memory effects in GaN HEMTs using active IF load-pull. Presented at: Asia-Pacific Microwave Conference (22nd : 2010), Yokahama-shi, Japan, 7-10 December 20102010 Asia-Pacific Microwave Conference proceedings : APMC 2010 : Dec. 7-10, Yokohama, Japan. Tokyo, Japan: Institute of Electronics, Information and Communication Engineers (IEICE) pp. 5-8.

2009

Wright, P., Lees, J., Benedikt, J., Tasker, P. and Cripps, S. C. 2009. A Methodology for Realizing High Efficiency Class-J in a Linear and Broadband PA. IEEE Transactions on Microwave Theory and Techniques 57(12), pp. 3196-3204. (10.1109/TMTT.2009.2033295)
Fitzpatrick, D. M., Lees, J., Sheikh, A., Benedikt, J. and Tasker, P. J. 2009. Systematic investigation of the impact of harmonic termination in the efficiency performance of above octave bandwidth microwave amplifiers. Presented at: European Microwave Conference, 2009 (EuMC 2009), Rome, Italy, 29 September - 1 October 2009European Microwave Week 2009 - "Science, Progress and Quality at Radiofrequencies": Conference Proceedings. London: Horizon House Publications pp. 1445-1448.
Cripps, S. C., Tasker, P., Clarke, A. L., Lees, J. and Benedikt, J. 2009. On the continuity of high efficiency modes in linear RF power amplifiers. IEEE Microwave and Wireless Components Letters 19(10), pp. 665-667. (10.1109/LMWC.2009.2029754)
Sheikh, A., Lees, J., Benedikt, J. and Tasker, P. J. 2009. Utilization of a measurement based CAD tool for enhanced pa design investigations. Presented at: 38th European Microwave Conference, 2008 (EuMC 2008), Amsterdam, The Netherlands, 27-31 October 2008Proceedings of the 38th European Microwave Conference, 2008 (EuMC 2008). Los Alamitos, CA: IEEE pp. 1671-1674., (10.1109/EUMC.2008.4751795)
Hashmi, M. S., Clarke, A. L., Woodington, S. P., Lees, J., Benedikt, J. and Tasker, P. 2009. Electronic Multi-Harmonic Load-Pull System for Experimentally Driven Power Amplifier Design Optimization. Presented at: IEEE/MTT-S International Microwave Symposium 2009, Boston, USA. pp. 1549-1552.
Wright, P. T., Lees, J., Tasker, P. J., Benedikt, J. and Cripps, S. C. 2009. An Efficient, Linear, Broadband Class-J-Mode PA Realised Using RF. Presented at: IEEE/MTT-S International Microwave Symposium 2009, Boston, MA, USA, 7-12 June 2009IEEE MTT-S International Microwave Symposium Digest, 2009. MTT '09. Los Alamitos, CA: IEEE pp. 653-656., (10.1109/MWSYM.2009.5165781)
Bensmida, S. et al. 2009. Power amplifier memory-less pre-distortion for 3GPP LTE application. Presented at: European Microwave Conference, 2009 (EuMC 2009), Rome, Italy, 29 September - 1 October 2009European Microwave Week 2009 - "Science, Progress and Quality at Radiofrequencies": Conference Proceedings. London: Horizon House Publications pp. 1433-1436.

2008

Alghanim, A., Lees, J., Williams, T., Benedikt, J. and Tasker, P. J. 2008. Sensitivity of electrical baseband memory effects to higher-order IF components for high-power LDMOS power amplifiers. Electronics Letters 44(5), pp. 358-359. (10.1049/el:20083348)
Alghanim, A., Lees, J., Williams, T., Benedikt, J. and Tasker, P. 2008. Reduction of electrical baseband memory effect in high-power LDMOS devices using optimum termination for IMD3 and IMD5 using active load-pull. Presented at: IEEE MTT-S International Microwave Symposium Digest, Atlanta, USA. pp. 415-418., (10.1109/MWSYM.2008.4633191)
FitzPatrick, D. M., Williams, T., Lees, J., Benedikt, J. and Tasker, P. 2008. Large signal device characterisation using active load-pull for improved MMIC design. Presented at: IET Seminar on RF and Microwave IC Design, London, UK. IET pp. 1-7.
Lees, J., Williams, T., Woodington, S., McGovern, P., Cripps, S. C., Benedikt, J. and Tasker, P. 2008. Demystifying Device related Memory Effects using Waveform Engineering and Envelope Domain Analysis. Presented at: 38th European Microwave Conference 2008 (EuMC 2008), Amsterdam, The Netherlands. pp. 753-756., (10.1109/EUMC.2008.471562)
Williams, T., Mojon, O., Woodington, S. P., Lees, J., Barciela, M. F., Benedikt, J. and Tasker, P. J. 2008. A robust approach for comparison and validation of large signal measurement systems. Presented at: IEEE MTT-S International Microwave Symposium Digest, Atlanta, USA. pp. 257-260., (10.1109/MWSYM.2008.4633152)
Woodington, S. P. et al. 2008. A novel measurement based method enabling rapid extraction of a RF waveform look-up table based behavioural model. Presented at: IEEE MTT-S International Microwave Symposium Digest, Atlanta, USA. pp. 1453-1456., (10.1109/MWSYM.2008.463305)
Wright, P. T., Lees, J., Tasker, P. J. and Benedikt, J. 2008. GaN power transistors in narrow and wide bandwidth applications. Presented at: IET Seminar on Wideband Receivers and Components, London, UK. pp. 1.

2007

Alghanim, A., Lees, J., Wiliams, T., Benedikt, J. and Tasker, P. 2007. Investigation of electrical base-band memory effects in high power 20w LDMOS power amplifiers. Presented at: 37th European Microwave Conference, Munich, Germany. pp. 48-51., (10.1109/EUMC.2007.4405122)
Sheikh, A., Tasker, P. J., Lees, J. and Benedikt, J. 2007. The impact of system impedance on the characterisation of high power devices. Presented at: 37th European Microwave Conference (EuMC), Munich, Germany. pp. 949-952., (10.1109/EUMC.2007.4405315)
Alghanim, A., Lees, J., Williams, T., Benedikt, J. and Tasker, P. J. 2007. Using active IF load-pull to investigate electrical base-band induced memory effects in high-power LDMOS transistors. Presented at: Asia-Pacific Microwave Conference (APMC 2007), Bangkok, Thailand. IEEE pp. 1-4., (10.1109/APMC.2007.4554737)

2006

Mayer, M., Arthaber, H., Magerl, G., Kother, D., Lees, J., Benedikt, J. and Tasker, P. 2006. Advanced load pull systems. Presented at: The Institution of Engineering and Technology Seminar on High Efficiency Power Amplifier Design for Next Generation Wireless Applications, Cambridge, UK. pp. 27-54.
Aubrey, A. J., Hicks, Y. A., Lees, J. and Chambers, J. A. 2006. Using the bi-modality of speech for convolutive frequency domain blind source separation. Presented at: Proceedings of IMA 7th International Conference on Mathematics in Signal Processing, Cirencester, UK.
Lees, J., Sheikj, A., Benedikt, J. and Tasker, P. 2006. The Design of a Gallium Nitride Doherty Amplifier using Waveform Measurements and Active Harmonic Load-Pull. Presented at: 2006 International Workshop on Integrated Nonlinear Microwave and Millimeter-Wave Circuits, Aveiro, Portugal. pp. 26-29.
Lees, J. 2006. Doherty amplifier structures for modern microwave communication systems. PhD Thesis, Cardiff University.

2005

Aboush, Z., Lees, J., Benedikt, J. and Tasker, P. J. 2005. Active harmonic load-pull system for characterising highly mismatched high power transistors. Presented at: IEEE MTT-S International Microwave Symposium Digest 2005, 2005. , (10.1109/MWSYM.2005.1516920)
Aboush, Z. et al. 2005. High power active harmonic load-pull system for characterisation of high power 100-Watt transistors. Presented at: 35th European Microwave Conference, Paris, France, Vol. 1. pp. 609-612., (10.1109/EUMC.2005.1608930)
Lees, J. et al. 2005. Experimental gallium nitride microwave Doherty amplifier. IEEE Electronic Letters 41(23), pp. 1284-1285. (10.1049/el:20053155)
Lees, J. et al. 2005. A comparison of load-pull measurement results of a 4W Phemt involving five European laboratories. Presented at: European Gallium Arsenide and Other Semiconductor Application Symposium, Paris, France, 3-4 October, 2005Proceedings of the European Gallium Arsenide and Other Semiconductor Application Symposium Paris, France,3-4 October, 2005. IEEE pp. 321-324.
Lees, J. et al. 2005. Characterisation of an experimental gallium nitride microwave Doherty amplifier. Presented at: 35th European Microwave Conference, Paris, France, 4-6 October 200535th European Microwave Conference: conference proceedings. Horizon House

2004

Lees, J., Haczewski, J., Benedikt, J. and Tasker, P. 2004. An automated multi-stimulus measurement system for characterising multi-device amplifiers. Presented at: 34th European Microwave Conference, Amsterdam, The Netherlands, Vol. Nov-15. pp. 435-438.

2003

Lees, J., Goss, M., Benedikt, J. and Tasker, P. 2003. Single-tone optimisation of an adaptive-bias Doherty structure. Presented at: Microwave Symposium Digest, IEEE MTT-S International, Philadelphia, USA, 8-13 June 2003Microwave Symposium Digest, IEEE MTT-S International, Vol. 3. IEEE pp. 2213-2216., (10.1109/MWSYM.2003.1210604)

I became a Fellow of the Higher Education Academy in 2014.

My teaching currently spans all years of Electrical and Electronic Engineering undergraduate and taught postgraduate programmes, as well as various pre-sessional and outreach programmes.

I lead four MSc / MEng modules; Research Project, HF-RF Engineering, Advanced CAD, Fabrication and Test, RF Design and CAD, as well as one first year module; Analogue Communications.

Other current and recent roles include:

Year 4 Tutor – MEng Integrated and Electronic Engineering (current)

Year 1 Tutor – Integrated and Electronic Engineering

MSc Tutor - Wireless and Microwave Communications Engineering (including variants – MRes & 2-year schemes)

MSc Tutor – Communications Technology & Entrepreneurship

MSc Tutor – Compound Semiconductor Electronics

I belong to the centre for high-frequency engineering (CHFE), a research group that has traditionally, and sucessfully focussed its research activities on commercial microwave communication systems, applications of compound semiconductors and more recently, resonant structures for sensing and disruption.

Compound semiconductor electronics - The CHFE is currently leading a number of groundbreaking research projects; an EPSRC funded consortium, involving numerous academic partners, developing high-efficiency, high-bandwidth envelope tracking (ET) RF modules for 5G communications systems, that require the close integration of RF and baseband electronics, using the same device technology ideally on the same GaN-on-silicon substrate. The CHFE also leads a major RF-GaN Supply chain project, GaNforCS, involving 10 industrial partners, transferring reseacrh understanding and know-how into industrial processes for volume production, enabling a UK source of RF-GaN devices for communications, security and healthcare applications.

Solid-state microwave heating and disruption - Cardiff University is a member of the radio frequency energy alliance (RFEA), a European consortium promiting the use of solid-state semiconductor technology for mass-market domestic and industrial heating and disruption applications. Current research explores the idea of multiple-feed solid state heating for microwave assisted curing of composites. There are significant benefits linked to the precise control achievable through solid-state microwave heating compared to the traditional, magnetron based and autoclave approaches.

Microwave assisted systems for healthcare - I have been involved with a number of collaborative research projects with the Schools of Dentistry and pharmacy, looking at ways in which we can use an applied microwave electrical field to a) inhibit the formation and growth of anti-microbial resistant biofilms, and b) the disruption of bacterial cell and spore to expose DNA for enhance rapid detection of antimicrobal resistant desiese. One example that is particulary important in terms of its potential impact, is the The Phoenix project is a Cardiff university gateway project in which the university is working with colleagues in Namibia to address some of the major healthcare problems which the country is currently facing. Of particular concern is the spread of antibiotic resistant tuberculosis with over 200,000 active cases at any one time. Treating the disease is particularly challenging as the current diagnostic methods lack sensitivity and speed and require access to infrastructure such as mains electricity. Given that many of the affected individuals live a nomadic life style, in areas remote from major centres of population, timely access to healthcare is a challenge.

In joint collaboration, the schools of Engineering and Pharmacy are developing a microwave based real-time point of care assay capable of detecting a range of pathogens, including tuberculosis, within a time frame which allows the patient to be diagnosed and appropriately treated during the same healthcare visit. To develop this capability, we aim to address three linked technical challenges;

The development of a simple and robust energy capture system capable of supporting the operation of the assay in areas of Namibia remote from mains power
A low-power microwave disruption system capable of mediating the release of target DNA from a range of clinical samples.
A simple to read, pathogen-specific lateral flow assay

The microwave disruption platform is based on solid-state microwave electronics and small single-mode resonant microwave cavities that focus a pulsed electrical field within a sample containing planktonic bacteria or bacterial spore, in order to lyse cells and liberate target DNA.

The use of solid-state microwave electronics is key to the success of this project, and importantly allows low-voltage battery and renewable energy solutions to be considered, suitble for remote field deployment.

The microwave hardware is continually being optimised, and recent research conducted at Cardiff School of Engineering has demonstrated that it is possible to reduce the size, weight and importantly the required microwave power levels dramatically, such that the power requirement for DNA extraction is now similar to that delivered by a mobile phone handset.

These advances, coupled with the high-efficiency microwave amplifier design techniques pioneered at Cardiff University, now provide the real possibility that the diagnostic tool envisaged could be powered locally using solar or simple hand-crank generators.

As part of this ongoing work, and in addition to the microwave elements, we will aim to develop a simple, mobile, electrical energy generation and storage system capable of quickly energising the diagnostic system. We will then look to deploy the combined system to Namibia and in partnership will colleagues from the school of Medicine of the University of Namibia, determine the ability of the system to detect TB in the field.

Research Contracts

Title	People	Sponsor	Value	Duration
GaNfoCS – Gallium Nitride for Communications and Security	Lees J, Elgaid K, Tasker P	WEFO-ERDF	£2.8M	01/01/2020 - 30/08/2022
Non-linear (large signal) millimetre-wave devices, circuits and systems on-water characterisation facility	PJ Tasker, R Quaglia, K Elgaid, J Bell, S Cripps, J Benedikt, J Lees	EPSRC	£1.5M	01/10/2018 - 01/09/2019
mm-wave power amplifiers for active antenna arrays	Quaglia R, Lees J, Cripps C	Huawei	£73k	01/11/2018 - 01/11/2019
Development of power management and storage and efficient detection and wireless transmission for SHM systems	Featherston C, Lees J, Pullin R	EADS	£200k	01/10/2011 - 30/09/2014
SENsors to Inform and Enable wireless NeTworks	Featherston C, Pullin R, Lees J, Holford K	TSB via HW Communications	£143k	01/01/2014 - 31/12/2016
Montagu	Featherston C, Pullin R, Lees J, Holford K	TSB - Innovate UK	£114k	01/05/2015 - 31/10/2017
Self-powered autonomous device for wireless structural health monitoring (SANDWICH)	Featherston C, Pullin R, Lees J, Holford, K	TSB	£40k	01/05/2013 - 31/10/2016
RF Power Amplifiers based upon Silicon-Germanium (SiGe) BiCMOS technology (studentship)	Tasker P, Lees J	SiGe Semiconductor (Europe) Ltd	£30k	01/10/2010 - 31/03/2014
Baseband linearisation schemes for high efficiency power amplifiers	Tasker P, Lees J	Infinion Technologies North America Corp	£35k	01/01/2015 - 31/12/2017
High performance buffers for RF GaN electronics	Tasker P, Lees J	EPSRC	£250k	01/10/2016 - 31/03/2020
Multi-Mode DI - ADC	Belcher R, Lees J, Naylon A	SELEX Galileo	£100k	01/10/2011 - 31/01/2013
High-efficiency device characterisation for OperaNET	Benedikt J, Lees J	Freescale Semiconductor	50000	01/10/2008 - 30/09/2011
Upgrading the small equipment base for early career researchers in the Engineering and Physical Sciences	Holford K, Whatling G, Lees J, Anderson P I, Brousseau E, Cipcigan L M, Pullin R, Bigot S, Theobald P, Simpson R N, Kawashita L F, Clarke A	EPSRC	498326	01/11/2012 - 31/03/2013
BST Capacitor characterisation	Lees J	ANALOG DEVICES	3500	10/12/2012 - 09/01/2013
Efficient Composite Curing by Intelligent Microwave Processing	Lees J, Evans SL, Porch A, Eaton M	EPSRC Centre for Innovative Manufacturing in Composites - CIMComp, via Nottingham	49069	01/05/2015 - 31/10/2015
To develop autonomous load cells through the development of power management electronics, wireless communication and energy harvesting technologies for a wide range of monitoring applications	Lees J, Pullin R, Featherston C, Eaton M	KTP and Flintec	122570	01/10/2013 - 30/09/2015
Development and Realisation of Novel, Broadband, High-Efficiency Power Amplifiers (studentship)	Lees J, Tasker P	Freescale Semiconductor France SAS	50000	01/01/2012 - 31/12/2014
High Performance power amplifiers for phased array radar and point to point communication applications	Lees J, Tasker P	M/A COM Technology Solutions (UK) Ltd	45000	01/10/2011 - 30/09/2014
Integrating High-Performance Power Amplifier with Miniturized Wideband Antenna for Highly-Efficient Future Communication Devices	Lees J, Tasker P, Cripps S	Ser Cymru NRN AEM Swansea	59350	01/10/2014 - 30/09/2017
Development and realisation of novel broadband high efficiency power amplifiers	Tasker P, Lees J	Freescale Semiconductors France SAS	50000	01/10/2012 - 30/09/2015
GaN electronics: RF reliability and detradation mechanisms	Tasker P, Lees J	EPSRC	222392	01/01/2013 - 31/12/2015
Integration of RF Circuits with High Speed GaN Switching on Silicon Substrates	Tasker P, Lees J, Benedikt J	EPSRC	835074	01/04/2016 - 31/03/2019
Characterisation and comparison of packaged GaN devises	Tasker PJ, Benedikt J, Lees J,	Cree Inc	16931	01/05/2008 - 01/09/2008
Dynamic Characterisation and modelling of RF GaN HEMTs	Tasker PJ, Lees J	Ser Cymru NRN AEM Swansea	81300	01/10/2014 - 30/09/2017
Develop an ultra rapid diagnostic system capable of detecting the presence of C. difficile in a clinincal sample at the bedside in under 10 minutes	Baillie L(PHRMY), Lees J, Porch A	Cardiff Partnership Fund	12022	01/09/2014 - 31/08/2015
Clean and Green Microwave heating using solid state physics	Cripps, S, Porch A, Lees J	NXP Semiconductors Netherlands B V	30000	01/10/2011 - 30/09/2014

Current Research Interests

I am interested in supervising PhD students in the areas of

High efficiency Power Amplifier Design
mm-wave power amplifier design
Microwave and mm-wave circuit design techniques
Medical applications of microwave engineering
Microwave and mm-wave characterisation

Current Students

Title	Student	Status	Degree
Device Level Characterisation of Out-phasing Power Amplifiers	Aleksander Bogusz	Current	PhD
Integrated Envelope Tracking Power Amplifiers for 5G communications	Alexander Alt	Current	PhD
Measurement-Based Non-linear Modelling for Active Devices	Zack Costello	Current	PhD
Integrating High-Performance Power Amplifiers with Miniaturised Wideband Antennas for Highly-Efficient Future Communications Devices	Elango Nagasundaram	Current	PhD

Past projects

Supervised Students

Title	Student	Status	Degree
A Modulated Active Load Pull Characterisation System for 5G	Sattam Alsahali	Graduate	PhD
Investigation of Novel Measurement Techniques for Microwave Devices	ALDOUMANI Anoor	Graduate	PhD
Solid-State Microwave heating For Biomedical Applications	IMTIAZ Azeem	Graduate	PhD
Re-configure high efficiency power amplifiers.	SHEPPHARD Daniel John	Graduate	PhD
Biomedical Applications of Microwave Engineering	SHKAL Fatma Ahmed	Graduate	PhD
Novel Power Amplifier Design Using Non-Linear Microwave Charcterisation and Measurement Techniques	OGBOI Friday Lawrence	Graduate	PhD
Baseband Linearisation Schemes for High Efficiency Power Amplifiers	WANG Guefeng	Graduate	PhD
Use of microwave technologies in the detection of pathogenic bacteria	HAMZAH Hayder Miri Hamzah	Graduate	PhD
Characterisation of Powders Using Microwave Cavity Perturbation	CUENCA Jerome Alexander	Graduate	PhD
Development of an efficient energy storage and power management for autonomous aircraft structural health monitoring system	THANGARAJ Karthik	Graduate	PhD
Power amplifier design for microwave heating applications	CHAUDHRY Kauser	Graduate	PhD
MICROWAVE CHARACTERISATION OF AMMINES FOR ENERGY STORAGE APPLICATIONS.	BARTER Michael	Graduate	PhD
RADIATION-BASED TECHNOLOGY TO ENHANCED MICROBICIDAL ACTIVITY OF BIOCIDES	PASCOE Michael	Graduate	PhD
High performance power amplifiers for phased array radar and point to point communication application.	KOH Minghao	Graduate	PhD
High Resolution Electric Field Probes With Applications In High Efficiency RF Power Amplifier Design	DEHGHAN Nelo	Graduate	PhD
USE OF NOVEL SENSING TECHNIQUES IN NEAR NETT SHAPE MANUFACTURING.	CLARK Nicholas Sebastian	Graduate	PhD
RF techniques applied to additive manufacturing	PARKER Nyle	Graduate	PhD
DEVICE CHARACTERISATION FOR WIDEBAND, HIGH EFFICIENCY POWER AMPLIFIERS	WILSON Richard Jason	Graduate	PhD
MICROWAVE PROCESSING IN ADDITIVE MANUFACTURING.	HEFFORD Samuel John	Graduate	PhD
ELECTROMAGNETIC PROPERTIES OF SEMICONDUCTING METAL OXIDES UNDER EXTERNAL STIMULATION.	PARTRIDGE Samuel Lee	Graduate	PhD
Sensors to Inform & Enable Wireless Networks	GRIGG Stephen	Graduate	PhD
DOHERTY AMPLIFIER WITH AID OF AD-HOC OPTIMIZATION FOR SDR APPLICATIONS.	KAMARUDIN Syalwani Binti	Graduate	PhD
The Auxiliary Envelope Tracking RF Power Amplifiers	YUSOFF Zubaida	Graduate	PhD
DEVELOPMENT OF A BROADBAND AND EFFICIENT LINEAR TRANSMITTER	A MOKHTI Zulhazmi Bin	Graduate	PhD