The Fractional Frequency Synthesizer Technology And It's Application

The thesis describes a prototype fractional frequency synthesizer which is supported by a project granted by the Ministry of Science and Technology of PR China. Firstly, based on the principle of PLL, this paper briefly describes three basic PLL components: Phase Detector (PD), Low Pass Filter (LPF), Voltage Controlled Oscillators (VCO) , analyzes the linearized PLL and summaries the transfer functions of third-order PLL with ideal intergrator filter respectively. Based on a microwave VCO, the single point frequency PLL frequency ranging from 2.2 to 2.5GHz is developed. Based on digital PLL, the S-band frequency synthesizer is manufactured. The characterstic of PLL , as well as the mathematical model of phase noise are also investigated. The paper presents the schematic of S-band frequency synthesizer and the main circuits modules upon which, by considering the Electromagenetic Comptiblity (EMC), fractional frequency synthesizer is fabricated by both PLL and DDS, the performance of the prototype product is carefully measured. Measuring results show that the product's performance meets the pre-assigned specifications .