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Wideband Doherty Power Amplifier with Designed Back-Off Power for Cellular Base Stations

Zafari, Ali | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52957 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Memarian, Mohammad; Safarian, Amin Ghasem
  7. Abstract:
  8. The Emergence of modern wireless communication standards and the need to use the frequency spectrum efficiently has made communication system designers exert complex modulation schemes. One of the results of such designs that has a direct impact on the design procedure of power amplifiers is that there will be signals with high peak to average power ratio.The obvious consequence of this manner in the design of communication systems would be the reduction of power amplifier efficiency due to its operation in its back-off region. The solution will be to use load modulated power amplifiers such as Doherty amplifier which brings up the problem of limited bandwidth.In this thesis, we tackle this bandwidth issue in Doherty power amplifiers. With the help of some simple calculations, we have defined an approach to compensate for the lack of bandwidth in Doherty power amplifiers. In the proposed idea, by placing two-port networks in the output (drain) of the transistors we design a compensator circuit that enhance the bandwidth of the whole Doherty amplifier. Then we implement a circuit realization of each two-ports at the output of main and auxiliary amplifiers which were defined by their mathematical relationships at first. So at the back-off power, we reached a fixed drain efficiency of π/4 over a 100 percent fractional bandwidth and limited its decrease to 0.85 of that value in the peak power.Finally, a sample single-band Doherty power amplifier at the frequency of 2 GHz is designed and presented by utilizing available transistors in Iran as a practice before designing the wideband Doherty amplifier
  9. Keywords:
  10. Doherty Power Amplifier (DPA) ; Dual Band Power Amplifier ; Peak to Average Power Ratio ; Load Modulation ; Frequency Domain Equalizer (FEQ)

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