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Digital predistorters for amplifier linearization
Kroužil, Miroslav ; Valenta, Václav (referee) ; Maršálek, Roman (advisor)
In this work I describe digital predistortion in baseband used for amplifier linearization. Non-linearity is one of the worst disadvantages of Power amplifiers and decreasing of its is useful from many reasons. Work examines system which contains: Data source, which is represented by QPSK or OFDM modulator, predistorter, Power amplifier (model of non-linearity) and unit used to update coeficients for predistorter adaptation. System is simulated in MATLAB and Xilinx (simulation by ModelSim). Results are compared, described and commented.
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Microwave Modulators Based on Sixports
Dušek, Martin ; Bezoušek, Pavel (referee) ; Galajda, Pavol (referee) ; Šebesta, Jiří (advisor)
This doctoral thesis is focused on problems of modulators based on six-ports. It begins with description of current state of the art of six-ports used like modulators, their transfer functions and SIW technology. A design part of this thesis consists from experimental six-port based on substrate integrated waveguide (SIW) technology. There is presented step-by-step development of this six-port using this technology and also there is introduced micro-strip technology based six-port. Final design of six-ports and variable impedances were measured, the results are discussed and compared with expected ones in next chapters. Second part of this thesis deals with influences of internal parameters of six-ports to final signal transmission and derives theirs transfer functions for more than one reflection in structure. The computation results are compared with experimental measurements for fixed loads. With using of ideal loads sweeps, modulations with shaped input signals were calculated. For designed variables impedances, there was founded the optimal biasing points for demanded IQ diagram and discussed which from tested active circuit is suitable. In the last part there are shown results of experiment with these variable loads connected to both types of designed six-ports.
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Microwave Modulators Based on Sixports
Dušek, Martin ; Bezoušek, Pavel (referee) ; Galajda, Pavol (referee) ; Šebesta, Jiří (advisor)
This doctoral thesis is focused on problems of modulators based on six-ports. It begins with description of current state of the art of six-ports used like modulators, their transfer functions and SIW technology. A design part of this thesis consists from experimental six-port based on substrate integrated waveguide (SIW) technology. There is presented step-by-step development of this six-port using this technology and also there is introduced micro-strip technology based six-port. Final design of six-ports and variable impedances were measured, the results are discussed and compared with expected ones in next chapters. Second part of this thesis deals with influences of internal parameters of six-ports to final signal transmission and derives theirs transfer functions for more than one reflection in structure. The computation results are compared with experimental measurements for fixed loads. With using of ideal loads sweeps, modulations with shaped input signals were calculated. For designed variables impedances, there was founded the optimal biasing points for demanded IQ diagram and discussed which from tested active circuit is suitable. In the last part there are shown results of experiment with these variable loads connected to both types of designed six-ports.
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Digital predistorters for amplifier linearization
Kroužil, Miroslav ; Valenta, Václav (referee) ; Maršálek, Roman (advisor)
In this work I describe digital predistortion in baseband used for amplifier linearization. Non-linearity is one of the worst disadvantages of Power amplifiers and decreasing of its is useful from many reasons. Work examines system which contains: Data source, which is represented by QPSK or OFDM modulator, predistorter, Power amplifier (model of non-linearity) and unit used to update coeficients for predistorter adaptation. System is simulated in MATLAB and Xilinx (simulation by ModelSim). Results are compared, described and commented.
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