Microwave Chirp Source Developed

A sort of LFM synthesizer with high resolution, wide bandwidth, low phase noise and fast frequency switching has been introduced. By adopting the hybrid "DDS+orthogonal modulation"frequency upconversion technology controlled by MCU. The performance of the system has been achieved.The main content comprised of MCU, DDS, PLL,Microwave switch and orthogonal modulation.Firstly, the developing background and trend of LFM synthesizer has been introduced, as well as the basic characteristics and synthesis method of LFM signal and the basic concept frequency synthesis technology has been presented.Secondly, The main theory of LFM synthesizer based frequency synthesis technology has been analyzed in detail, mainly including: DDS technology, PLL technology,Microwave switch and orthogonal modulation technology. Then the scheme of LFM synthesizer has been put forward based on these theories.Thirdly, the scheme has been demonstrated roundly. DDS chip AD9854 PLL chip ADF4113,VCO ROS₁200W orthogonal modulation chip AD8345 and microwave switch chip HMC349 have been selected by according to the need of system:frequency switching time the phase noise,bandwidth,resolution and SFDR.Finally the debugging process has been introduced. The result has been analyzed detailed.Specifications of LFM synthesizer show as following: output frequency range 675-715MHz, phase noise -108dBc/Hz@10kHz,SFDR -50dBc,step 0.05MHz, hopping time 0. 8μs,output power -6dBm.