Towards multi-dimensional terahertz imaging systems based on low-cost silicon technologies

In this work, novel system concepts offering multi-dimensional imaging capabilities are investigated, which provide new modalities for the implementation of millimeter-wave (mmWave) and terahertz (THz) systems based on silicon technologies. Providing 3-D imaging with additional frequency diversity, 4-D imaging at THz frequencies is approached in the current work. The technique of using continuous wave (CW) radiation for mmWave/THz imaging has been studied for several decades, but only recently semiconductor-based mmWave/THz transceivers have reached the point, where the devices can be compact and fully integrated. Electronic III-V-based mmWave/THz devices show generally better performance than their competitors implemented in silicon. However, silicon-based transceivers offer such advantages like high level of monolithic integration, co-integration of digital processing units, low quality variation within series production of multi-pixel sensor matrices, and low-cost production at higher volumes. Thus, in order to overcome the limitations of the currently available silicon technologies being operated in the THz regime, optimized transceiver architectures and novel system concepts are in need. The results presented in this work reach well beyond the state-of-the-art in silicon-based imaging systems. Hence, the developed and realized amplitude and phase imaging system operating at 160 GHz, the circularly polarized radar systems operating at 240 GHz provide an outstanding performance in terms of system SNR, antenna beam quality, achievable range resolution, and module compactness combined with advantages offered by the modern efficient and low-cost SiGe HBT technology. The multi-frequency-band imaging system where the operating frequency spans from 160 GHz to 1 THz completes the targeted system approach for frequency diversity with spectroscopic capabilities that is successfully implemented in a SiGe HBT technology. Therefore, the here derived conclusions build a basis for the implementation of future low-cost, compact, robust, and fully electronic multi-pixel THz sensing systems for such industrial applications like the non-destructive quality and package control, for the civil security, and for various spectroscopic applications.