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Visar resultat 1 - 5 av 33 avhandlingar som matchar ovanstående sökkriterier.

  1. 1. High efficiency power amplifiers for wireless communications

    Författare :Hossein Mashad Nemati; Chalmers tekniska högskola; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; load modulation; GaN; supply modulation; LDMOS; efficiency; Power amplifier; MMIC; mHEMT; transmitter architecture;

    Sammanfattning : This thesis presents state-of-the-art high efficiencyharmonically-tuned power amplifiers (PAs) and investigates thecharacteristics and potentials of such amplifiers in two of the mostpromising efficiency enhancement techniques, dynamic supply and load modulation.In this work, a 10 W LDMOS harmonically-tuned PA with 80% power-added-efficiency (PAE) isrealized at 1 GHz. LÄS MER

  3. 2. High-efficiency Power Amplification Techniques for Wireless Transmitters

    Författare :Hossein Mashad Nemati; Chalmers tekniska högskola; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; load modulation; LDMOS; supply modulation; GaN HEMT; Power amplifier; wireless communications.; GaAs mHEMT; efficiency;

    Sammanfattning : The low efficiency of existing power amplifiers (PAs) is causing excessive energy consumption in wireless systems. Improving the PA efficiency is therefore of great environmental and economical importance. LÄS MER

  4. 3. High Efficiency Microwave Amplifiers and SiC Varactors Optimized for Dynamic Load Modulation

    Författare :Christer Andersson; Chalmers tekniska högskola; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; nonlinear measurements; power amplifiers; load modulation; GaN; SiC; varactors; HEMT; wide bandgap technology; energy efficiency;

    Sammanfattning : The increasing use of mobile networks as the main source of internet connectivity is creating challenges in the infrastructure. Customer demand is a moving target and continuous hardware developments are necessary to supply higher data rates in an environmentally sustainable and cost effective way. LÄS MER

  5. 4. Power System Oscillations - Detection, Estimation and Control

    Författare :Morten Hemmingsson; Industriell elektroteknik och automation; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Elektroteknik; oscillation; power system; damping; power swing; distance protection; detection; estimation; real-time; reactive co-variation; control; Electrical engineering; load modulation; Automation; robotics; control engineering; Automatiska system; robotteknik; reglerteknik;

    Sammanfattning : The topic of this thesis is the electro-mechanical oscillations which to some extent always are present in a power system. The demand of electric power is ever increasing. At the same time, the tolerance of disruptions in the power supply is decreasing. LÄS MER

  7. 5. Modulation of tumor sensitivity to effector mechanisms of cytotoxic lymphocytes

    Författare :Kristian Hallermalm; Karolinska Institutet; Karolinska Institutet; []
    Nyckelord :Tumor escape; cytotoxic lymphocytes; interferon-gamma; TNF-alpha; granzyme B; Perforin; Fas ligand;

    Sammanfattning : Today, ample evidence demonstrates a clear role for the immune system in the battle against cancer. However, the relatively high rate of mutation and proliferation of tumor cells, in combination with the selective pressure exerted by the immune system, can potentially lead to the generation of genetically altered tumor cells, which are able to evade recognition by the immune system and continue to grow and form tumors. LÄS MER