Terahertz Signal Source and Receiver Operating near 600 GHz and Their 3-D Imaging Application

In this article, a set of oscillators and a heterodyne image receiver operating near 600 GHz have been developed, each based on a 250-nm InP heterojunction bipolar transistor (HBT) technology and a 130-nm SiGe HBT technology, respectively. The oscillators are based on the common-base cross-coupled push-push topology, which employed coupled-line loads for improved output power and efficiency with a small area. The measured oscillation frequency ranges of the three oscillators with different coupled-line lengths were 628-682, 556-610, and 509-548 GHz, respectively, with a tuning capability achieved with bias variation. The maximum output power and the dc-to-RF efficiency achieved with the oscillators were -10 dBm and 0.19%, respectively. The heterodyne receiver, which consists of a mixer, an IF amplifier, and an IF detector, exhibited a maximum responsivity of 469 kV/W and a minimum noise equivalent power (NEP) of 0.64 pW/Hz1/2. A transmission-mode 3-D THz tomography imaging setup was established with one of the fabricated oscillators and the heterodyne receiver employed as the signal source and the image detector, respectively. With the imaging setup, a successful reconstruction of 3-D images of a target object was demonstrated based on the filtered back-projection algorithm.