Research On Key Techniques Of Deformation Measurement Based On Radar Differential Interferometry

The deformation measurement based on differential interferometry of radar can be used in monitoring the deformation of structures such as tower,bridge and dam,it can reach the deformation measurement effect of long distance,non-contact,and multipoint,thus it has great potential in the field of deformation monitoring.Based on the pulse compression of the linear frequency modulation continuous wave and differential interferometry theory,the system designed of deformation measurement based on radar and some key technologies of radar information processing are researched in this paper.Firstly,the principle of the radar based on the linear frequency modulation continuous wave signal was introduced in this paper,and then the parameter of the deformation update and the influence of different signal structures to the deformation update was analyzed.Then the two common radar receives—the structure of zero intermediate frequency and fixed intermediate frequency were compared in this paper,so the new radar receive was designed combined the advantages of the two common receives and the practical use of our new radar,the new radar system is based on the orthogonal modulation,it can avoid a lot of problems,such as the local oscillator leakage,dc offset and so on,and solve the problem of the zero drift of the circuit at the same time.Secondly,since the complex conditions of the scatterer within the radar radiation scope,the existence of the stationary clutter seriously affected the precision of deformation monitoring.The reason for the formation of a stationary clutter and the influence because of the existence of the static clutter were analyzed in this paper,the way based on circular curve fitting to remove static clutter so as to improve the precision of deformation monitoring was researched,then the designed experiment verified the existence of stationary clutter and influence,and then verified the precision of deformation monitoring was improved significantly after the removal of static clutter.And then,as a result of the radar relative to traditional deformation monitoring method has the advantages of can monitoring multiple points at the same time,the methods of how to extract multiple targets at the same time was studied in this paper.The method of extracting targets according to the scattering intensity was researched first,and it was validated by the experimental data,the effect of this method can extract the strong scattering points in the line of sight direction of the radar,which suitable for the deformation monitoring where the environment is simple,then the method of extracting the targets compared the scattering intensity and the error of the circular curve fitting was researched on that basis of the way of circular curve fitting to remove static clutter,the effect of target extraction of this method was validated by the designed simulation experiments,the target which was extracted in the radar line of sight direction were deformation occurred obviously,which suitable for the deformation monitoring where there are a lot scatterers and only those targets deformation occurred.Finally,the error sources of the deformation monitoring are summarized and classified.According to the mathematical performance of the errors,these errors can be divided into the zero mean error and the slowly accumulated errors.How to adjust these errors were researched after removing the zero mean errors,the slowly accumulated errors include the errors which comes from the change of the temperature of the radar system and the change of the atmospheric meteorological parameters which affect the refractive index of electromagnetic wave in the open air.Experiment was designed and conducted to verify the method can effectively reduce the influence of the error and greatly improve the precision of deformation monitoring after the research on how to adjust the lowly accumulated errors.