Research On Ka-band Low Phase Noise Frequency Source

Millimeter wave radar is widely used in aerospace,ship-borne,UAV and other fields.As one of the key components of millimeter wave radar,it is of great application value to study and design the frequency source of millimeter wave radar.The frequency source with low phase noise can enhance the detection accuracy and imaging accuracy.However,the volume,power consumption and cost of the instrument frequency source are very large,and it is not suitable for millimeter wave radar in shipboard and aerospace environment.The remote phase noise of frequency source obtained by PLL or direct frequency synthesis can not meet the requirement of low phase noise frequency source for radar system with large dynamic range and high selectivity.The phase noise of the frequency source synthesized by only using PLL can only meet the requirements of low-band radar application scenarios.If the frequency of the PLL chip is doubled to Ka-band,the phase noise cannot meet the requirements of largerange and high-selectivity radar system in Ka-band.The frequency synthesis method of direct frequency doubling can achieve low phase noise at the near end,but the phase noise at the far end can not meet the demand,and the frequency range is narrow.Based on the above background,a Ka-band low phase noise frequency source is designed in this paper.In order to ensure low phase noise at the far end and a wide frequency conversion range,this thesis uses a point frequency source signal generated by harmonic frequency multiplication to build a phase-locked loop to reduce the phase noise at the far end,and then further uses multiple up-conversion methods to design a ka-band low phase noise frequency source.This project is mainly divided into two parts:(a)The point frequency source part is realized by harmonic frequency doubling and local frequency phase-locked loop.The step diode harmonic frequency doubling is first used to generate 1 GHz point frequency signal,and then the local frequency phase-locked loop built by voltage controlled sound surface wave oscillator(VCSO)is used to improve the remote phase noise of 1 GHz signal.(b)The up-conversion part is realized by multiple frequency doubling and filtering.First,the output frequency reaches the Ka band through triple frequency doubling and single frequency quadruple,and then the millimeter-wave frequency source of 28-29 GHz is realized through mixing.Finally,the output frequency of 28～29 GHz is realized,the output power is between-18～-20 d Bm,the output power flatness is less than 3 d B,the performance of spurious suppression in the frequency band is good,the spurious suppression degree in the 10 GHz bandwidth is more than 50 d Bc,phase noise at 28.5 GHz frequency is-82.78 d Bc/Hz@1k Hz,-83.41 d Bc/Hz@10k Hz,-115.62 d Bc/Hz@1MHz.