Novel highly efficient broadband continuous power amplifier modes

The power amplifier is one of the most important and crucial component of the wireless networks due to its high power consumption. For this reason, in the last 20-30 years many scientists from all around the world have addressed the issue of how minimising such power consumption, which means maximising the PA efficiency as well as gain while delivering the expected power and the appropriate linearity for the specified frequency. Nowadays due to the continuous demand of wireless services, PAs with high power-efficiency for the specified narrow band frequency are not enough. Such PAs have to be capable to deliver satisfactory output performance for the wide spectrum frequency. For this reason, the work presented in this thesis is focused around the PA stage and describes a new way to design broadband power amplifiers used in the wireless communication systems. For the first time this work presents what have been termed “Continuous Modes”. It is known that for delivering high efficiency states, output high harmonic impedances must be taken into account. However, the knowledge of where such harmonic terminations should be once found the singular optimum fundamental load would deliver the high efficiency condition but will not reveal information in terms of bandwidth. In this work it is demonstrated that if varying the reactive part of the fundamental impedance from the optimum condition and adjusting reactively the high harmonic terminations in accordance with the Continuous theory applied to the different PA classes, a new “Design Space” where the output performance remains theoretically constant can be achieved. Furthermore, varying both reactively and resistively the fundamental load and again adjusting the magnitude and phase of the high harmonic terminations a yet wider design space would be revealed with the output performance slightly degraded from the optimum condition but still giving satisfactory performance. The degradation of such performance is balanced to the fact that now new alternative solutions are revealed allowing more flexibility in the PA design. Now the PA designer can decide which new impedances to target if designing narrow band PAs or he can decide to target more solutions for which broadband PAs can be realised. Broadband Continuous PAs - Vincenzo Carrubba - xii The research presented in this thesis shows the theoretical Continuous Mode theory applied to the various PA classes supported by experimental measurement results using the Waveform Engineering Time Domain Active Envelope Load-Pull system developed at Cardiff University applied to different transistors technology and sizes. Besides, a Continuous Class-FV PA delivering around 10.5 W of average power, 11 dB of average gain and 65-80% of drain efficiency for an octave bandwidth between 0.55 GHz and 1.1 GHz has been designed and realised.