Highly-Stable Microwave Synthesis And Frequency Transfer And Their Application To Bistatic SAR

Highly-precision,highly-stable microwave frequency sources are an important part of the beam atomic clock system.The beam atomic clock locks the electrical oscillation signal to the Atomic ground state hyperfine transition to achieve extremely high stability frequency output.The highly-stable frequency source is the basis of communication,navigation,metrology,deep space exploration,basic scientific research,etc.It is also an important guarantee for national defense and national security.At present,the atomic frequency standard system including commercial cesium beam atomic clock has been embargoed on China by western countries,and the research significance of highly-stable microwave frequency sources is to break through the technical blockade of western countries in the field of atomic frequency standard and to contribute to the localization of atomic clocks.Highly-stable microwave frequency signal generated in the laboratory are transmitted by laser in the atmosphere or underwater to achieve high-precision frequency transmission,which provides theoretical and experimental support for the construction of the transmission link of the atmospheric or underwater atomic frequency standard signal,and has important scientific significance and application value.Highly-stable microwave frequency signals generated in the laboratory,high-precision frequency transmission through the laser in the atmosphere or underwater,providing theoretical and experimental support for constructing the transmission link of atmospheric or underwater atomic frequency signals,with great scientific significance and application value.The combination of atomic frequency-based microwave frequency generation and laser-based atmospheric high-precision frequency transmission is applied to the synchronic-Aperture Radar(SAR)local oscillator signal synchronization,which can be used when the GPS is subject to human interference or cut-off.Providing a new phase synchronization method is of great significance for national security and emergency response to natural disasters.The combination of microwave frequency generation based on atomic frequency standard and highly-precision frequency transmission based on laser through atmosphere is applied to synchronize the local oscillation signal of bistatic synthetic aperture radar(SAR),which can be used when the GPS is subject to human interference or cut-off providing a new phase synchronization method with great significance for national security and emergency response to natural disasters.This thesis focuses on the research of highly-stable microwave frequency synthesis based on atomic frequency standard,highly-precision free space atmosphere and underwater frequency transmission based on laser,and bistatic SAR local oscillator signal synchronization.The aim is to break the foreign blockade of China in related technical fields.The main contents are divided into four parts shown as follows.(1)Research on high-stability microwave frequency generation.The theoretical model of high-stability microwave frequency synthesis is developed,analyzed and simulated based on Dielectric Resonator Oscillator(DRO)technique.The structure of the frequency multiplier combined with the double-phase-locked loops is designed to realize the signal generation.The phase noise and phase tracking time of the output signal is measured in detail.The test results show that the absolute phase noise characteristics are almost equal to the theoretical value at the offset carrier frequency of 1 Hz and 10 Hz.As a first application,the Opto-Electronic Oscillator(OEO)based atomic frequency standard generation technology was researched and analyzed.And single-ring structure OEO frequency generation device was designed and built,and the absolute phase characteristics were measured in detail.Exploratory research was carried out for high-stability frequency synthesis technology based on OEO structure.As a first application,based on the above research,a dual-mode Ramsey cavity for a dual Rb/Cs atomic clock was designed and measured in detail which provides a reference for the practical application of a dual Rb/Cs Ramsey microwave cavity.As followed,combine the high-stability microwave frequency and the Ramsey microwave cavity tor use in the atomic clock system.The frequency instability of the high-stability microwave frequency was measured and the result showed that the instability was on the same of the atomic clock.(2)Research on continuous-laser-based atmospheric free space frequency transfer technique.The theory of atmospheric frequency transfer is deeply studied,and turbulence-affected timing fluctuation over free space optical links is analyzed in detail,and the theoretical model of atmospheric frequency transfer is established.A continuous-laser-based atmospheric frequency transfer with sub-picosecond timing fluctuation using single phase compensator setup is proposed for the first time.The experimental results show that the electrical phase compensation technique effectively compensates the timing fluctuation.The frequency transfer experiment shows the compensated free space frequency distribution link has instability of 2 × 10-13 @ 1 s and 2×10-16@ 1000 s.The Alan variance is two or three orders of magnitude lower than that of the commercial cesium beam atomic clock(5071A),providing powerful theoretical and experimental support to disseminate atomic clocks over atmospheric free space link.(3)Research on continuous-laser-based underwater frequency transfer technique.The effects of different water bodies on underwater frequency transfer link are studied and we also analyzed the problems of underwater frequency transfer.Using the theoretical model of atmospheric turbulence,the influence of underwater turbulence on frequency transfer is evaluated,and the root mean square(RMS)value of phase jitter in different transfer distances is obtained as the experimental verification reference value.The experimental setup of the underwater frequency transfer system was designed,and the transfer distances of 3 m,6 m and 9 m were measured,respectively.Then the measurement results were compared and analyzed.On this basis,the continuous laser underwater frequency transmission technology based on electrical phase compensation is proposed for the first time.The experimental results show that the electrical phase compensation technique effectively compensates the timing fluctuation.The RMS timing fluctuation for a 100 MHz frequency transfer over a 5 m long underwater link with phase compensation was measured to be approximately 2.1 ps within 5000 s with a fractional frequency instability on the order of 5×10-13 @ 1 s and of 7×10-16@1000 s.The instability of the underwater transmission link with the distance of a few meters is superior to Cs atomic clocks which implies the atomic clock is able to be directly distributed over underwater link in a short-range.(4)High-stability microwave frequency and atmospheric frequency transfer technique in the phase synchronization of bistatic SAR(Synthetic-Aperture Radar)local oscillator.The requirements of frequency and phase synchronization of the bistatic SAR system are introduced,and the influence of synchronization error on bistatic SAR imaging is analyzed in detail.Combined with the high-stability microwave frequency generation technology and the laser-based atmospheric frequency transfer technique,the synchronization scheme of the local oscillator signals frequency and phase of the bistatic SAR system is designed.Then,the real data in the atmospheric frequency transfer experiment is used to carry out an in-depth simulation analysis of the synchronized bistatic SAR system.The experimental results demonstrate the feasibility of applying high-stability microwave frequency generation technology and atmospheric frequency transfer technique to the synchronous bistatic SAR local oscillators.