The Research Of Microwave Nondestructive Testing And Imaging Algorithm

Nowadays Microwave imaging has become an advanced research field in application electromagnetism. It is a no-contact method in study objects properties by using microwave technique, electronic technique and digital processing technique. Microwave imaging is also a kind of nondestructive testing technique, the research of which is according to the measured scattering data to reconstruct the image of material dielectric constant. Shining with the microwave field of the low power at first, the scattering field is measured and the image can be reconstructed with the data. Different from the traditional nondestructive testing technique such as the ultrasonic, X-ray, etc.,it is according to the density of the material but electromagnetism properties. It has strong penetrating ability. At microwave frequency bands, the electromagnetism properties of different materials change more sensitively than other physical properties. This is the superiority by using microwave. Microwave imaging is still at developing stage and its future depends on the improvement of microwave technologies and perfect imaging algorithm.Microwave imaging has extensive uses in military and civil affairs. In the civil respect, microwave imaging is widely used in industry nondestructive testing, the earth explore, object recognition, national safety inspection and so on. There are enormous application prospects in medical science, too. The subject is subsided by scientific and technological department of Liaoning Province in 2002. Distributions situation of reinforcing bar in the concrete wall can be detected by microwave nondestructive technique. It can also be used in the testing of bridgeboard, pier, road surface and the structure of living beings. There are also important meanings to guarantee the quality of the project and the security of the structure of the building.The paper includes the study of microwave function mechanism, the determination of microwave device structure, receiving experimental data, the research of microwave imaging algorithm. In the earlier stage, the structure of the testing device had been determined by studying the microwave theory. Then the scattering data are received by finite elementsimulation and the distribution situation of reinforcing bar within the concrete is reconstructed with a kind of w-k algorithm. Then data-gathered card is designed and the satisfied result has been achieved by using the real device to detect the concrete model (450mm x350mrnx250 mm). The paper includes five chapter altogether. The principle of MNDT and microwave imaging, the development of MNDT at home and abroad, the transmitting of plane wave and the classification of different medium are described in detail in the first and second chapter. Those contents are all foundations of following study. The third, forth, fifth chapters are the key parts of the thesis. In chapter three, the foundation of all microwaves image reconstruction algorithms isfigured out from basic Maxwell--the integral equation of the scattering. Some kinds ofmicrowave image algorithms have been probed into and the background of application has also been described. In chapter four, software ANSYS of finite element in the MNDT application study has been analyzed and the results of reconstructed images are given by simulated data. And then the design of the software and hardware of data-gathered card is described. At the same time, the result of reconstructed image is also given by the actual data. At last, the conclusions of the paper and the good application foreground of microwave nondestructive technology are discussed, and then some suggestions are put foreword to in the future research.