Research And Realization Of A High-performance VHF Frequency Synthesizer Based On DDS Hybrid PLL

Frequency synthesizer is an important component of the modern electronic system and widely used in communications, radar and navigation equipment. DDS have high frequency resolution, low-output phase noise, but frequency output is low; PLL have poor phase noise when resolution is high, but have better performance in spurious and higher output frequency. DDS hybrid PLL can take good advantage of both their merit, have become an important area of frequency synthesis.Research of DDS hybrid PLL concentrated in multiple-frequency approach, which is relatively simple structure, but the phase noise and spurious of DDS will become worse, especially when high output frequency is needed. Resolution is change with different N. Research of DDS mixed with PLL is virtually blank. Because DDS no lock-in PLL frequency, does not exist phase noise and spurious deteriorating, and frequency resolution is only decided with DDS. But, the designed and achieve of high frequency broadband filter is difficult.This paper presented a new high-performance DDS hybrid PLL VHF frequency synthesizer based on mix thinking. The DDS mixed with the VCO output in the PLL feedback path, have two improvements with traditional frequency synthesizer: 1. DDS take the place of the low-frequency loop of the Multi-PLL. Maintain the DDS output phase noise and spurious level unchanged. Frequency resolution is not changes when N is different.2. Design sliding LC filter rather than fixed broadband high-frequency band-pass filter. Frequency range of the synthesizer is 89.6~110.4MHz, resolution is 1Hz, spurious character is better than . Finally, offer some technical references to application and development on frequency synthesis techniques. -90dBc /Hz@10kHz...