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A software-defined radio (SDR) allows for digital communication systems to easily adopt more sophisticated coding and modulation technologies, which is extremely important in meeting the ever-increasing demands of the wireless communication industry. In this study, an SDR has been constructed using Xilinx system generator tools and implemented on the Virtex-II Field Programmable Gate Array (FPGA). The Xilinx system generator allows for fixed-point logic system design, hardware/software co-simulation, and board implementation through a model-based approach. In the SDR, Quadrature Phase Shift Keying (QPSK) is chosen as the modulation scheme for demonstration. Through a wireless link, the QPSK signal experiences amplitude attenuation, frequency and phase shifts causing rotation of the signal constellation. A phase-locked loop (PLL) circuit is designed for carrier and symbol synchronization for recovery of data from the received signal. In order to resolve the phase ambiguity of the QPSK system, a differential encoding scheme is also implemented.