Study And Realization Of The Frequency Synthesis Technique Of The Modern Coast Defense Radar Based On DDS

The development of the frequency synthesis technique is reviewed firstly in this paper, and then the direct digital frequency synthesis technique and its scattering is studied deeply and the spectrum features of the ideal output signal of the direct digital frequency synthesizer is analyzed.A implementation method is introduced for X band frequency synthesizer with low phase noise, low scattering, wide frequency and agility on the basis of DDS technique for coast protection. This method combines the local programmable logical device FPGA and CPLD,and classical DDS method to generate IF frequency scale cohort of P band and the chirp signal with variable time width/band width for realize the expert target via replacing the frequency multiplication, frequency division and mixing by program optimization and reasonable electromagnetic compatibility design. The actual test result is shown that the method is to be good practice and it is a important progress for traditional frequency synthesis. It has the certain theories meaning and actual reference value for the total amount word turns the frequency synthesis system engineering design.The detailed three-proofing design is explained in this paper for it has high requirement for moisture-proof, salt fog proof and mould proof because of coast protectoin.The paper is wrote through the stages of information collection, subject determination, system demonstration and feasibility analysis, system engineering design, adjustment and test, and system specification achievement. The test datas show that the system achieves that the phase noise <-110dBc/Hz@1kHz, scattering≤-70dBc, frequency hopping time≤300ns and the harmonic suppression≥65dB in X band.