Digital Communications is the physical transfer of data (a digital bit stream) over a point-to-point or point-to-multipoint communication channel. The data is often represented as an electromagnetic signal, such an electrical voltage signal, a radio wave or microwave signal or an infra-red signal. While analog communications represents a continuously varying signal, digital transmissions have to be broken down into discrete messages. The messages are either represented by a sequence of pulses by means of a line code (base band transmission), or by a limited set of analogue waveforms (pass band transmission), using a digital modulation method. Maximum requirement with any communication system is fast and correct transmission. To satisfy correctness, we need to synchronize in carrier and time of signal, this thesis deals mainly with synchronization in time. The objectives of the thesis are: (1) design a specific diagram for timing synchronization with QPSK signal, (2) from received results, judge ability to develop it in the future. The environment Matlab - Simulink and System Generator of Xilinx are selected to design in my thesis, it can be said that they are the most popular tools for research and developed environment.

In terms of structure, the thesis has four chapters. Chapter 1 presents the overview of FPGA and digital modulation concern to QPSK signal. Chapter 2 is aimed to review theoretical background of synchronization techniques in digital communication. Particularly, this chapter is concerned with the differential coding, basic circuits for synchronization in time and carrier. Specific designs for timing synchronization with QPSK signal is focus of chapter 3. Finally, chapter 4 is where results are discussed, conclusions are drawn out and applications of the research findings are indicated for the communication systems.