Study On X-band Phase-locked Frequency Synthesizer

Almost all of the electronic equipments in working order need any one of a number of operating frequencies generated by frequency synthesizers. They assume an important role in electronic equipments which is similar to the human heart. While frequency synthesizers are employed widely in various equipments, they still represent a fascinating and challenging area of electronic design. With the electronic design has become more and more complex, the design of frequency synthesizers is also facing more challenges. Therefore, conducting abundant research on frequency synthesis and finding the optimal design is of great significance.The thesis starts with the introduction of the research background, and then gives an overview of the development of frequency synthesis at home and abroad. The basics of frequency synthesis are elaborated afterward. Based on the theoretical analysis, an X-band sampling PLL is designed. A parallel feedback DRO is designed and used as VCO in the SPLL so as to avoid the risk of a false lock. Sampling phase detector is implemented by the commercial chip MP7100. The acquisition-aid circuit uses a Wien bridge oscillator to generate the sweeping voltage. Then the SPLL is employed in an X-band frequency-hopping source design. The architecture is a dual-loop synthesizer which consists of the external loop and the internal loop, namely the SPLL. The output of the SPLL is divided by two and then mixes with the output of the VCO in the external loop. The IF output is fed to the PFD in the external loop. The reference signal of the external loop comes from the output of a DDFS chip AD9911. In the external loop, a DAC circuit is designed to pre-tune the VCO. In addition, an MFC application is programmed in order to debug the system. The internal loop eliminates the effect of the noise floor of the divider, and the external loop has small divider ratio. The system can be easily debugged by the MFC application.According to experimental results, the output frequency of the X-band SPLL is 9.5 GHz while the output power is 9.3 d Bm. The output phase noise achieves-99.34 d Bc/Hz at 10 k Hz offset. The frequency range of the X-band frequency-hopping source is from 10.7 GHz to 11.7 GHz with a frequency resolution of 10 MHz. The out phase noise is better than-89.48 d Bc/Hz at 10 k Hz offset while the output power achieves 10 d Bm. Experimental results are in line with the theoretical analysis, which demonstrates that the analysis is correct and the design is feasible.