Designing a digital QPSK modulator with software radio technology

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Fehér Gábor
Department of Broadband Infocommunications and Electromagnetic Theory

The fast evolution of the wireless communication systems brought the need for a new technology, which enables the characteristics of an already built radio system to be modified even during operation. The solution is the SDR architecture, which meets the needs of the former problem, also reduce the cost and the time of the development phase. The base of the SDR technology is the software implementation of some parts of the physical layer, the baseband signal, and also the signal on the power amplifier is obtainable by the reconfigurable device. The baseband signal is always based on a modulation technique, and it could be BPSK, QPSK, or QAM.

The thesis presents the process of digital phase modulation, and its features in the frequency range. The importance of the applied filters, the problem of phase inaccuracy, and one possible solution are also discussed. Then the simulation model of QPSK modulator is presented, followed by the realization of the modulator with the help of the SDR technology.


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