Silicon-Based sub-THz Radiometers for Passive Imaging

This paper presents three silicon-based 100 GHz radiometer chips for passive imaging, including a total power radiometer and two types of Dicke radiometers. The total power radiometer consists of a high gain low noise amplifier (LNA) and a high-responsivity detector. Besides the LNA and the detector, the two Dicke radiometers include an additional passive SPDT switch and a proposed SPDT amplifier respectively. The above radiometers are fabricated in two different $0.13 \mu \mathrm {m}$ SiGe BiCMOS technologies, which feature comparable $f_{\mathrm {T}}/ f_{\max}$. The measurement results demonstrate a typical LNA gain of 35–45 dB utilizing 4 cascode stages, a typical responsivity of 27.2 kV/W, a typical noise equivalent power of around $2.5\,\mathrm{pW/\surd Hz}$ at 91 GHz. Utilizing the SPDT amplifier, the Dicke radiometer demonstrates a switching loss as small as 0.93 @ 91 GHz, which leads to a noise equivalent temperature difference (NETD) as small as 0.21 K@30 ms.