Broadband Millimeter Wave Circular Scanning Turntable Imaging Technology Research

Millimeter-wave, which has the advantages of both centimeter wave and infrared wave, not only is capable of penetrating into non-metallic luggage and clothes, but also creating high resolution imaging. Therefore, more and more attention is gotten in the fields of security inspection and medical diagnosis, and it will become a crucial and non-contact security means to implement the imaging detection for the contraband of luggage and clothes through millimeter-wave in the future.Conventional millimeter-wave security inspection imaging system, which usually combines linear array technique with mechanical scanning to obtain data collection, makes use of synthetic aperture formed by large-sized electronic scanning and mechanical scanning to realize two-dimensional high resolution imaging. Due to large-sized linear array needs more antenna arrays and transceiver channels, the cost of these imaging systems tends to be much higher, which restricts application and popularization of these kinds of systems. Therefore, it is imperative to develop a low-cost millimeter-wave security imaging scheme. This paper presents a millimeter wave imaging system based on single-channel circularscanning method, which can reduce the cost. In addition, we also conducts an experiment to verify its effectiveness. This system consists of a single-channel system with only a pair of antennas. One of the antennas is used to transmit the millimeter wave signal to the target and the other one is utilized to receive the return signals. The antennas are located at a certain height over the circular trace formed by the target. Thus, the antennas which regard targets as center to scan with oblique view, can collect all-around return data of targets, and then achieve objects imaging through back projection algorithm. Compared to traditional linear array imaging system with numerous array elements, this system with low cost and small size just needs a pair of single transmitting and receiving antennas. It differs from small angle imaging system of traditional SAR and ISAR and collects objects return data from 360-degree scattering information with a high resolution as well as reflecting multi-angle image information of objects.We have demonstrated the imaging experimental platform with vector network analyzer, horn antenna and high precision turntable and achieved automatic data collection and turntable control. During the experiment, return datas of materials with different attributions such as scissor, kitchen knife, pistol model, water and oil at Ka-band and W-band are collected. We processed measured datas with algorithm of circular back projection in MATLAB. The results indicate that this system has a good performance and verifies its imaging ability for hidden hazardous objects. Meanwhile, it displays promising perspective in human body security imaging.