Chessboard FPA in 130-nm SiGe BiCMOS for High-Resolution Passive Terahertz Imaging
Year: 2026
Type: article
Abstract: This work presents a chessboard focal plane array (FPA) camera with state-of-the-art thermal and spatial resolution in the$200$–$600 \,\mathrm{G}\mathrm{Hz}$frequency range. The FPA is implemented in a$130$-$\mathrm{n}\mathrm{m}$SiGe BiCMOS technology, where each antenna element is loaded with a direct detector based on heterojunction bipolar transistors (HBTs). The antenna and detector architecture, including the vias and biasing network, were optimized to achieve a noise-equivalent power (NEP) suitable for passive$\mathrm{T}\mathrm{Hz}$imaging. Overall, the estimated loss of the FPA is better than$4 \,\mathrm{d}\mathrm{B}$between$350$and$600 \,\mathrm{G}\mathrm{Hz}$, of which$1.5 \,\mathrm{d}\mathrm{B}$is due to ohmic losses in the FPA,$1 \,\mathrm{d}\mathrm{B}$to mutual coupling between detectors, and$0.7 \,\mathrm{d}\mathrm{B}$to the impedance mismatch between the detector and antenna. A prototype of$24$pixels was manufactured and mounted on the base of a silicon hyperhemispherical lens with an anti-reflection coating. Excellent spatial resolution is achieved through a tight element spacing in the fabricated FPA, which is only half the wavelength in silicon at$350 \,\mathrm{G}\mathrm{Hz}$and therefore consistent with the state-of-the-art. Its responsivity, noise, and radiation patterns were characterized using a quasi-optical measurement setup. The measured radiation patterns are within$1 \,\mathrm{d}\mathrm{B}$of simulations, demonstrating that the integrated$\mathrm{T}\mathrm{Hz}$camera achieves excellent spatial resolution. Between$330 \,\mathrm{G}\mathrm{Hz}$and$500 \,\mathrm{G}\mathrm{Hz}$, the NEP was measured to be on the order of$10 \,\mathrm{p}\mathrm{W}\mathrm{/}\sqrt\text{Hz}$. When considering the entire operational band, this NEP results in a noise-equivalent temperature difference (NETD) of the camera is$1.6 \,\mathrm{K}$for an integration time of$1 \,\mathrm{s}$per pixel, which is comparable to the state-of-the-art. While$\mathrm{T}\mathrm{Hz}$detectors with state-of-the-art sensitivity are limited to single-pixel designs, the presented work combines a multi-pixel implementation with competitive sensitivity.
Source: IEEE Journal of Microwaves
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,075
OpenAlex ID: W7128767937