Overview
I discovered high frequency engineering during my BEng degree in Kaiserslautern, Germany and have been fascinated by it ever since. That lead to my employment as R&D engineer at TRUMPF Huettinger in Freiburg, developing RF power amplifiers, splitters, combiners and measurement techniques. In 2015, I decided to return to academia for a MSc course in Wireless & Microwave Communication Engineering at Cardiff university, where I decided to stay to work towards a PhD. My research interests are high efficiency power amplifier structures, espcially envelope tracking power amplifiers, transistors for those structures and system level considerations in mobile communications.
Publications
2021
- Alt, A. 2021. Supply modulated GaN HEMT power amplifiers - From transistor to system. PhD Thesis, Cardiff University.
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)
- 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. 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)
- 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., 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)
- 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)
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)
- 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)
- 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)
- 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.
- 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)
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)
- 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)
- 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. -.
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)
- Alt, A., Schwerg, N., Wangler, C. and Gruner, D. 2017. Concept for the implementation of very high directivity and decade bandwidth in compact microstrip directional couplers. Presented at: 2016 46th European Microwave Conference (EuMC), London, UK, 3-7 October 20172016 46th European Microwave Conference (EuMC). IEEE pp. 210-213., (10.1109/EuMC.2016.7824315)