A Multiband Terahertz Detector in 65-nm CMOS for Spectroscopic Imaging

This article proposes a low-area multiband terahertz (THz) detector structure for spectroscopic imaging, which consists of several narrow-band THz detectors with different detection frequencies. By combining the output of the narrow-band detectors, broadband detection is realized. The detection frequency can be expanded by adding more narrow-band detectors with different detection bands. To reduce the whole area of the detector, a loop antenna is used in each narrow-band detector to realize a nestable architecture, where the high-frequency antennas are successively placed in the low-frequency antennas with the same center position. The area is determined only by the narrow-band detector with the lowest detection frequency. Each of the narrow-band detectors adopts a conventional self-mixing detection structure, including an FET-based power detection circuit, an on-chip loop antenna, and a matching network. Two spiral structures are proposed as the matching network to improve the performance of each narrow-band detector. Using the multiband detector structure, a detector with eight frequency bands has been implemented in the 65-nm CMOS process, which achieves effective detection in the 75–1100 GHz range with an area of only 244 × 244 μm². A peak voltage responsivity (R_v) of 1.4 kV/W and a minimum noise equivalent power of 17 pW/Hz^1/2 are achieved. A set of spectrum analysis experiments and imaging experiments verify the practicability of the multiband detector structure.