Abstract-Three-Dimensional Terahertz Tomography With Transistor-Based Signal Source and Detector Circuits Operating Near 300 GHz

Jungsoo Kim,  Daekeun Yoon,   Jongwon Yun,  Kiryong Song,   Mehmet Kaynak, Bernd Tillack,   Jae-Sung Rieh

https://ieeexplore.ieee.org/document/8399538/

In this paper, three-dimensional (3-D) terahertz (THz) tomography was demonstrated with a signal source and imagers based on transistor circuits fabricated with standard semiconductor technologies. For the signal source, a 300-GHz oscillator based on InP HBT technology was employed. For detection, two types of imagers operating near 300 GHz were employed, one direct and the other heterodyne, both realized with SiGe HBT technology. With a set of 2-D images taken from different angles, sinograms and tomograms were obtained, which led to a successful reconstruction of 3-D images of the target object based on the filtered back-projection algorithm. A systematic comparison was made for the direct imager and the heterodyne imager, for which the signal input power and the video bandwidth were varied for both imagers. The results revealed that the heterodyne imager shows a better sensitivity than the direct imager. However, a similar dynamic range of around 30 dB was achieved for both imagers because of a saturation observed for the heterodyne imager when the input power exceeds the threshold. The video bandwidth did not affect the image quality significantly for the bandwidth variation over four orders of magnitude for both imagers.

Abstract-300-GHz Direct and Heterodyne Active Imagers Based on 0.13-μm SiGe HBT Technology

Daekeun Yoon, Jungsoo Kim,   Jongwon Yun, Mehmet Kaynak,  Bernd Tillack, Jae-Sung Rieh,

http://ieeexplore.ieee.org/document/7962297/

300-GHz direct and heterodyne imagers based on a 0.13-μm SiGe HBT technology were developed for active imaging applications in this work. The direct imager, which is based on the square-law principle, shows a maximum responsivity of 6121 V/W and a minimum noise equivalent power (NEP) of 21.2 pW/Hz1/2 at 315 GHz. The heterodyne imager, which consists of a mixer, a local oscillator, an IF amplifier, and an IF detector, exhibits a maximum responsivity of 322 kV/W and a minimum NEP of 3.9 pW/Hz1/2 at 300 GHz. Total dc power consumption of the direct imager is 0.6 mW, while the heterodyne imager consumes 21 mW. The chip areas of the direct and heterodyne imagers including the on-chip antenna are 460 × 410 and 610 × 610 μm2, respectively. To compare the performance of the two types of imagers for imaging applications, images from both imagers were acquired and compared with various output power levels of the signal source. It was demonstrated that the heterodyne imager shows much better image quality, especially when the signal source power is not sufficiently high.