Jiefeng Zang

Passive Millimeter Wave Imaging System Based on Helical Scanning.

A simple and fast single channel passive millimeter wave (PMMW) imaging system for public security check is presented in this paper. It distinguishes itself with traditional ones by an innovative scanning mechanism. Indoor experiments against human body with or without concealed items in clothes show that imaging could be completed in 3 s with angular resolution of about 0.7°. In addition, its field of view (FOV) is adjustable according to the size of actual target.

A new design of 3D electromagnetic inverse scattering imaging system

Summary form only given. In a 3D electromagnetic inverse scattering imaging system, the illuminating zones of different array elements may not necessarily overlap, as shown in Fig. 1. On the other hand, the imaging domain covers the superposed area illuminated by each and every element. Therefore, the active dimension of the imaging domain corresponding to each array element is much smaller than that of the imaging domain. Significant ill-posedness is therefore present in the governing equations. In view of the above problems, a new 3D electromagnetic imaging system as shown in Fig. 1 is proposed, which can be used in some special situations, such as fault inspection and clinical medical imaging. In this system, these are two identical arrays excited by coherent sources. One of arrays is called reference array, which illuminates the standard sample, while the other one is probe array, which illuminates the object to be imaged. The difference between signals received by the two arrays must come from the difference between the sample and the object. Difference image between the sample and the object will then be reconstructed if the difference signals are used as measurement data. As a matter of fact, it is exactly the information of our interest.

Low cost phase calibration in millimeter wave imaging system

In millimeter wave imaging systems, a slight displacement in the system may cause great phase error because of its short wavelength. In addition, different working conditions and aging rate may also bring deviation of phase and amplitude in each channel. In this regard, channel calibration, especially phase calibration is critical for millimeter wave imaging system.