A novel bandpass filter fed antipodal tapered slot antenna for millimeter wave imaging

Abstract

In this paper, we propose antipodal tapered slot antenna with integrated bandpass filter over 23.5-40 GHz for high resolution imaging applications. The novel antenna feed comprises of half mode substrate integrated waveguide and rectangular slots with isosceles trapezoidal variation. The feed section gives a passband over 23.5-40 GHz with S 11 j j< À10 dB and S 21 j j'0 dB. We present the design evolution procedure for the integrated filter antenna. The proposed antenna exhibits S 11 j j< À10 dB over the controlled bandwidth from 23.5 GHz to 40 GHz. We incorporate rectangular corrugations in the form of a staircase at the outer edges of the antenna and ground plane slots to achieve a stable gain and stable radiation pattern over the controlled bandwidth. The proposed antenna occupies a volume of 30.3 Â 16 Â 0.254 mm 3 , and is fabricated and tested. The measured results show good agreement with simulations. As compared to the state-of-the-art approaches, the proposed antenna is compact in size and exhibits a constant gain and stable radiation pattern over the operating bandwidth. We describe case studies to illustrate the application of the proposed antenna in a wideband imaging system for the detection of concealed objects and material defects. The reconstructed images obtained with the proposed antenna demonstrate its potential for use in high-resolution millimeter wave imaging systems.antipodal tapered slot antenna, half mode substrate integrated waveguide, integrated filter antenna, millimeter wave imaging | INTRODUCTIONIn recent years, noninvasive imaging has been deployed in various industrial, commercial, medical, and security applications. They include through-wall imaging, biomedical imaging, detection of concealed objects, security scanners, nondestructive testing of materials for fault detection, and detection of landmines and unexploded ordnance. Owing to their nonionizing nature and capability to detect nonmetallic objects, microwave and millimeter wave imaging systems have emerged as good alternatives to the conventional X-ray scanning technology. As less-crowded large bandwidth is available at higher frequencies, imaging systems at these frequencies benefit from their small size and a higher spatial resolution. The latter is crucial to capture the minutest details during imaging. While capturing a high-resolution image, the wide bandwidth signal is directed towards the target with the help of a high gain and wideband antenna. Given a target for imaging, the directivity, gain,