-Band Total Power Radiometer Performance Optimization in an SiGe HBT Technology

摘要

A $D$-band SiGe HBT total power radiometer is reported with a peak responsivity of 28 MV/W, a noise equivalent power (NEP) of 14–18 ${hbox{fW/Hz}}^{1/2}$, and a temperature resolution better than 0.35 K for an integration time of 3.125 ms. The $1/f$ noise corner of the radiometer is lower than 200 Hz. Fabricated in a developmental technology with 270-GHz $f_{T}$ and 330-GHz $f_{rm MAX}$, it includes a five-stage low-noise amplifier (LNA) with 4–7-GHz bandwidth and over 35 dB of gain centered at 165 GHz, along with a square-law detector with an NEP below 6 ${hbox{pW/Hz}}^{1/2}$ up to 170 GHz. An average system noise temperature of 1645 K is obtained using the $Y$-factor method and a noise bandwidth of 10 GHz calculated from the measured $S21(f)$ characteristics of the radiometer. The reduced $1/f$ noise corner frequency in the presence of the amplifier, compared to that of the detector, appears to indicate that, unlike in III–V radiometers, LNA gain fluctuations are not a problem in SiGe HBT radiometers. The circuit consumes 95 mW and occupies ${hbox {765}},times{hbox {490}}~mu{hbox {m}}^{2}$. Wafer mapping of the radiometer sensitivity and of the amplifier gain was performed across different process splits. The mapping results demonstrate that the radiometer can be employed as a r-nlatively simple and area-efficient transistor noise-measure monitor, useful in SiGe HBT vertical profile optimization.