Monolithically Integrated C-Band Low-Noise Amplifiers for Use in Cryogenic Large-Scale RF Systems

This article reports on the design of C -band (4-8 GHz) monolithically integrated low-noise amplifiers (LNAs) in a 50-nm metamorphic high-electron-mobility transistor (mHEMT) technology with low-dc-power consumption dedicated to cryogenic operation in large receiver arrays. Two LNA monolithic microwave-integrated circuits (MMICs) are investigated: one two-stage design (LNA 1) targeting the C -band, which has been designed as a stand-alone and as a four-channel MMIC to demonstrate the ability to achieve higher integration levels. The second amplifier (LNA 2) is a three-stage design focusing on 6-9 GHz, but it can also be used from 4-9 GHz with only minor performance degradation. LNA 1 achieves an average in-band noise temperature of 2.7 K with 31 dB of gain when operated at 10 K with optimal noise bias (7.78-mW dc-power consumption). The power consumption of LNA 1 can be reduced to 0.77 mW with an average noise of 3.8 K and 23.7 dB of gain. LNA 2 provides 44.5 dB of small-signal gain and 3.3-K average noise temperature between 4 and 9 GHz (2.9 K between 6 and 9 GHz) at 10 K and optimal noise bias (5.57 mW). When the dc-power consumption of LNA 2 is reduced to 1.34 mW, 35.4 dB of small-signal gain and 4.4 K of average noise temperature are preserved. To the best of the authors' knowledge, LNA 1 demonstrates both the lowest noise temperature and dc-power consumption among monolithically integrated C -band LNAs at cryogenic temperatures.