Polyphase Symbol Timing Synchronization on a Software-Defined Radio
Abstract: Software-defined radio is a continuously developing technology applied in fields of mobile communications and among others. It is a radio communication system where software is used to implement parts of its functionality in an embedded system or computer. Devices which can transmit and receive different radio protocols based on software has major advantages. The ability to be able to reconfigure and change functionality on the fly to adapt to different environments is suited for multiple different applications, one of such is the environment in space. Distortions such as phase, frequency and timing offset all occur in such environment. The effects of these distortions can be reduced using different synchronization techniques in the receiver. A polyphase symbol timing synchronizer with two different timing error detectors, is designed in Simulink consisting of an 8-tap polyphase filter bank, a zero-crossing or Gardner timing error detector, a second order Phase-locked loop and a numerically controlled oscillator. The initial design uses floating-point precision. A fixed-point model is implemented using Xilinx System Generator and is used to generate a custom IP. Simulation is done by implementing a transceiver model with Simulink for the transmitter and parts of the receiver. The polyphase symbol timing synchronizer locks after about 4000 symbols for lower signal-to-noise and the Gardner timing error detector performs better than the zero-crossing error detector at higher signal-to-noise ratios.
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