Development of cryogenic 0.7–1.8 GHz low noise amplifier

<p indent="0mm">The receivers of radio telescopes demand an extremely low system noise temperature. The InP HEMT devices, with their excellent noise and gain performance at low temperatures, possess outstanding advantages in the development of cryogenic low noise amplifiers. Driven by the requirements of Xinjiang Qitai Radio Telescope (QTT), this paper presents a <sc>0.7–1.8 GHz</sc> hybrid integrated cryogenic amplifier module based on independently fabricated InP HEMT devices. Firstly, we conducted on-chip DC and RF parameter measurements for the core InP HEMT device and established a small-signal model for the device. Subsequently, we designed a two-stage cascaded circuit with source degeneration and ensured the stability of the amplifier by using a bias filtering network and inter-stage isolation structure. Finally, the amplifier module was tested at an ambient temperature of <sc>15 K,</sc> demonstrating a gain of over <sc>30 dB</sc> and an average noise temperature of <sc>8.3 K.</sc> This paper verifies cryogenic performance of the independently fabricated InP HEMT devices and processes, laying a foundation for the subsequent development of cryogenic ultra-wideband MMIC amplifiers in QTT.