S-band Frequency Synthesizer Developed

The technology of frequency synthesis is not only one of the key techniques of radar communication systems, but also the basis of the modern Electronic Measurement devices. The performance of the radar communication systems greatly depend on the characteristics of frequency synthesizers. The technology of frequency synthesis originated in 1930s, and it has get the great development and improvement right now. Following the appearance of kinds of techniques, the technology of frequency synthesis was developed by the initial direct frequency synthesis into the indirect frequency synthesis and direct digital frequency synthesis. Currently, hybrid frequency synthesis techniques, which combine the indirect frequency synthesis and digital frequency synthesis, play an important role in today's field of electronic communications.Based on the background of frequency synthesis, the operation principles of phase locked loop (PLL) frequency synthesis and direct digital synthesis (DDS) are introduced in this thesis. Meanwhile, the mathematical model of the phase noise and the reasons for the formation of DDS spurious are also analyzed. After these, according the requirements of the project, this paper brings the proof of the system, carries out theoretical calculations and experimental simulation, and finally adopted the plan of PLL+DDS to realize a S-band frequency synthesizers with small step ,low phase noise and low spurious. And frequency synthesizer design and debug process has also been analyzed and notes.