An L-band Frequency Synthesizer with Fine Step Size
Min Jie · Radio Engineering of China · 2007
Firstly the basic theory of DDS and PLL,as well as their characteristics and phase noise properties,has been analyzed in detail.Combining the DDS and PLL technology is a method to achieve fine step size without degradation of spurious characteristics.The integrative frequency synthesis technology of DDS+PLL+Mixer is adopted in the final scheme.According to the request of the scheme,DDS chip AD9850 and the PLL chip ADF4112 have been chosen to establish the system circuit.Finally,experimental results are introduced.Its specifications show as following:output frequency at L -band,phase noise -94dBc/Hz@1kHz,spurious -60dBc,step size 1kHz.So the feasibility has been verified.