Phase Unwrapping In Inteferometric Synthetic Aperture Radar

Radar Remote Sense technology has become a hot research in Space-to-Ground Survey and also been widely used since it was proposed. With the advantages of 'all-weather' and 'round-the-clock', Radar Remote Sense becomes very important and active, especially the method named Interferometric Synthetic Aperture Radar (InSAR), which provides a new way to acquire the 3D information of the earth's surface.SAR can capture the Radar image like photography even in the worst weather condition. InSAR extracts the phase information from Radar image to calculate 3D information and heights change of the earth's surface. It is an active microwave sensor, which was proposed in 1950's and first used in aircraft-carried imaging. It can provide surveillance for activities of earthquake, volcano and iceberg etc as well as survey and map Earth. Furthermore, it can sense the heights of other planets' terrain. InSAR is a promising measurement, and its advantages include 3D imaging in all-weather and round-the-clock, high resolution, wide side-glance and strong perspective etc.This paper focuses on the phase unwrapping, one of the key steps of InSAR's data processing. First, the interferential imaging's principle in InSAR and the computer simulation are discussed. Next, the phase unwrapping method of interferential map of InSAR is studied, and one algorithm based on reliability guided and another algorithm based on fringe frequency analyses are proved to be effective in unwrapping InSAR's phase pattern, after using them in processing the practical and simulated phase data respectively and producing good phaseunwrapping results. The main achievements as follows:1. After elucidating the radar imaging principle of SAR, which includes the key theory of imaging, fundamental rules of imaging and the particular properties of radar side-glance imaging, the phase unwrapping algorithms are discussed in detail and the differences of those algorithms are also listed.2. A new model to simulate the InSAR imaging is proposed according to its principle and characters, which can quickly produce the copies of InSAR's target as well as its interference patterns.3. The sources of the noise of the interference fringe are discussed, as well as the corresponding filtering test for simulated noise. The circle-period-mean filtering algorithm is verified by good experimental results.4. A new phase unwrapping algorithm, which takes correlation coefficients as the guide of reliability sorting, is compared with other algorithms. The better results show this one can contain the false data in local region and can guarantee the correct restoration of the interference phase pattern.5. A new phase unwrapping algorithm based on fringe frequency analyses is proposed. First, it produces reliability mask by analyzing fringe frequency. And then a sorting algorithm based on this mask can restrict the phase unwrapping error in the smallest region. The principle, flow chart and design of the algorithm are explained detailedly. It can be another good choice in InSAR's phase unwrapping.