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On Efficiency and Bandwidth Enhancement of Integrated Class-J Power Amplifiers

Alizadeh, Amir Reza | 2016

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 49611 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Medi, Ali
  7. Abstract:
  8. Power amplifiers (PAs) are one of the key components in radio-frequency (RF) and microwave systems. In these systems, PAs must be highly efficient to simplify the thermal management and to enhance dc power requirements. Future systems, including WiMax, 4G, 5G, and beyond, will likely require larger bandwidths due to their wider spectral allocations caused by the extended bandwidth of baseband signals. Therefore, highly-efficient and broadband PAs are needed to be employed in these systems. To realize high-efficiencies over wide frequency ranges, class-J mode of operation was introduced by Cripps in 2009. Class-J mode of operation is capable of maintaining a high efficiency (78% in theory) over a broad bandwidth (100% in theory). There are few works in the literature about class-J PAs as not much time have passed since the introduction of class-J mode. In this thesis, class-J mode of operation is investigated in terms of drain efficiency and bandwidth, and some methods have been proposed and validated to enhance the performance of class-J PAs. The following techniques are suggested to increase the drain efficiency and power-added-efficiency (PAE) of class-J PAs: 1) Waveform engineering at the gate node of class-J PAs2) 2nd-harmonic current injection to the gate node of class-J PAs 3) Class-J2 power amplifiers In this study, for the first time introduction and experimental validation of class- J2 mode power amplifiers is presented. This newly-presented mode features a higher output power, efficiency, and bandwidth compared to class-J mode operation. The bandwidth performance of class-J mode PAs is also discussed in this thesis. The following issues are studied for the bandwidth topic: 1) Impact of the nonlinear drain-source resistance of transistor (RDS) on the bandwidth of class-J mode 2) Distributed class-J power amplifiers (DJPAs) For the first time, class-J mode of operation is introduced in design of distributed power amplifiers (DPAs) to achieve high power added efficiencies (PAEs) over wide frequency ranges. The proposed DJPA is implemented on a MMIC process to show that class-J DPAs achieve a higher efficiency than conventional class-A or -AB DPAs. In addition to DJPA, an octave-bandwidth (f=3.5–7 GHz) class-J power amplifier is also designed and implemented. The nonlinear RDS as well as its impact on class-J specifications is carefully taken into account while designing this PA
  9. Keywords:
  10. Power Amplifier ; Broadband Amplifier ; Improving Efficiency Method ; Class J Power Amplifier ; Highly-Efficient Amplifiers ; Continous Mode

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