Broadband Low Phase Noise Microwave Frequency Synthesizer And Key Technologies

As the most crucial techniques that apply in electronic systems, a high performance frequency synthesizer is absolutely necessary that ensure modern electronic systems such as radar and communication systems to achieve high performance. By the development of modern electronic communication technology, higher requirements have been presented on various targets of frequency synthesizer such as phase noise, frequency-hopping and Stepped-Frequency. Low noise and spurious suppression are the points of the wideband low phase noise frequency synthesizer, and it is important to study the design technology of low noise and spurious suppression of the wideband frequency synthesizer.The article analyses and studies the wideband low phase noise frequency synthesizer mainly. Firstly, the basic theory and characteristics of various frequency synthetic technologies have been introduced, the characteristics of phase noise and spur and the design technology of low noise and spurious suppression have been analysed.Secondly, the scheme has been demonstrated roundly based on the basic theory and analysis. The feasibility about the phase noise, SFDR, hopping step, has been analyzed, the key technical problem in mixing PLL, such as SFDR, intermediate frequency filter and Loop filter, is carried out. Finally,through the EMC design of the layout and grounding, the requests have been achieved by debugging all the whole circuits and programs time after time. Its specifications show as following: output frequency range 6570～7970MHz, phase noise is superior to -100dBc/Hz@10kHz, SFDR is superior to -70dBc, frequency-hopping is superior to 80μs. So the feasibility has been verified.In the study process of the wideband low phase noise microwave frequency source, the following key technologies have been forwarded and effectively applied:The technology of low phase noise:Assigned the frequency of signals,chose the phase detector and VCO with lowest phase noise,paid more attentain to modules'impedance match,designed and debuged aboratively the PLL filter and decreased the transmission deteriorate are the measures adopted,which make the phase noise superior to -100dBc/Hz@10kHz and -110dBc/Hz@100kHz in 7970MHz.The technology of low SFDR: Distributed the cavity effectively,optimized the layout, strengthened the design of electro magnetic compatibility especially the crosstalk suppression, added the trap circuit to restrain the spur close to the carry and etc are the measures adopted,which make the SFDR superior to -70dBc.The technology of miniaturization: The narrow cavity was distributed effectively according to the module's function and frequence characteristics and the components used in the scheme was choosen aboratively. And so the cavity fulfills the demand and is small as to 200×100×22mm~3.