Offset-PLL based frequency up-conversion for low spurious transmission

University essay from Linköpings universitet/Institutionen för systemteknik

Abstract:

The goal of this final year project is to investigate various techniques to up-convert a baseband signal into radio frequency signals, and to investigate the practical problems encountered in an offset phase locked loop design by implementation.

Phase locked loops are commonly used in radio transmitters and receivers to generate accurate RF signals from a low-frequency reference. This thesis will highlight some of the problems and strengths of various up-conversion schemes, and suggest an offset-PLL architecture free from many of those problems.

An offset-PLL is often used in mobile communication systems where the required levels of out of band transmission are tough and the use of superheterodyne up-conversion cannot be used due to spectrum or bandwidth requirements.

However a drawback of an offset-PLL is the high locking time; this can render the offset-PLL useless in TDMA communication systems. This problem among others has been studied theoretically as well as practically on an actual implementation of an offset-PLL for mobile communications. The offset-PLL was designed and manufactured as part of this project.

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