Research On Temporal Imaging Based On The Time-lens

In order to adapt to the rapid development of the broadband and ultra-wide band communication and radar technologies,and then accomplish the real-time processing of broadband and ultra-wide band signals,the research on analog signal processing technology has become increasingly active in recent years.The temporal imaging technology based on time lens has attracted extensive attention,because it can broaden,compress or invert the signal with arbitrary waveform in the time domain in real time.The temporal imaging technology was first introduced into the optics and was applied to the fields such as the precision diagnosis of the ultrafast optical pulses,real-time spectrometer and so on.In recent years,the microwave temporal imaging has greatly developed.In this dissertation,the basic principles of temporal imaging are researched,the performances of it are analyzed,and the key parameters to improve the performance of microwave temporal imaging system are revealed.A new kind of dispersion delay structure is proposed and used into the microwave temporal imaging.The final microwave temporal imaging system has a duration of 10 ns and a bandwidth of 1GHz.The main research contents of this paper are as follows:In the first chapter,the backgrounds and significances of temporal imaging technology are introduced.Then the development of temporal imaging in the optics reviewed and several methods of optical temporal imaging compared.After that,the dispersion delay structures,which are the most part in the microwave temporal imaging,are introduced and compared.In the second chapter,the theory of temporal imaging is reviewed and improved.There are two basic concepts,which are the space-time duality and the time lens,in temporal imaging.The practical time lens is not ideal and its time duration(time lens aperture)is finite.The time lens aperture effect will generates the resolution and quality factor of temporal imaging,which are the two important parameters.In addition,the aperture brought out the filtering effect of the temporal imaging.The principles of microwave temporal imaging are same as that of the optical,except some details.Finally,the relationship between the performance of the microwave temporal imaging and the parameters of the time lens along with the dispersion delay structure is studied.In chapter 3,considering that the group delay slope of the existing dispersion delay structures is small,a group delay dispersion structure based on the reflecting-type all-pass equalizer is proposed..At first,the performance of the most basic class C-type all-pass equalizer are analyzed,and then the cascade composed of a number of C-type all-pass equalizers is proposed to achieve a prescribed group delay response.Finally,the asymmetric high-order all-pass equalizer is proposed to provide the group delay response with better performance.In chapter 4,the microwave temporal imaging is realized.One reverse imaging system reverses a triangular wave with a duration of 8 ns or a multimodal pulse with a duration of 10 ns.One broaden imaging system double a pulse with a duration of 10 ns.In chapter 5,the synthetic aperture imaging is discussed.In temporal imaging,the longer time lens aperture bring out the higher resolution..A time lens with an extreme long aperture is difficult to directly obtained,and can be synthesized with several independent aperture time lens.The independent aperture time lens images the certain band of the input pulse respectively,then the outputs are superimposed after the image shift compensation.The synthetic aperture imaging is accomplished.At the end of this chapter,a 160 ps synthetic aperture is achieved by two 80 ps independent aperture and width.The sixth chapter is the summary and prospect of the whole paper.