A Cryogenic L-band Low-noise Amplifier

The design details for a cryogenic L-band low-noise amplifier are presented. This amplifier will be used on Shanghai astronomical observatory L-band cryogenic receiver that is building by NFRA (Netherlands Foundation for Research in Astronomy). The whole circuits design, including schematic input, simulation, optimization and PCB layout, are realized on the microwave EDA platform Agilent's ADS (Advanced Design System). The noise measurement method and equipments for the cryogenic applications are described. The first amplifier was finished at NFRA microwave technique laboratory in May 2004 and the prototype was test at room ambient temperature and at 15K (Kelvin). Commercial GaAs pHEMT transistors, Agilent ATF-35143, were used in this 2-stage amplifier. At a physical temperature 15K the amplifier achieves noise temperature between 3.2K and 3.8K over 1600MHz to 1740MHz band. The measured amplifier gain ranges from 28.7dB to 28.9dB with a total power consumption of 28mW. The input power matching is better than –22dB, i.e. VSWR 1.2:1. Ultra-low noise temperature, flat gain, good input power matching, low-power consumption, and unconditional stability make this amplifier suitable for cryogenic L-band receiver. At room temperature, the amplifier has a noise temperature of 35K, and gain is of 27.8-28.0dB.