Long-term stability of an SiGe HBT-based active cold load

摘要

In this study, results of long-term stability of an Active Cold Load (ACL), realized at L-band with an SiGe heterojunction bipolar transistor are reported. The ACL exhibits return loss higher than 35 dB and a noise temperature less than 66 K. A noise injection radiometer has been developed to perform the measurements. A noise-equivalent delta temperature of less than 31 mK and a stability estimated to 25 mK during 95 s were obtained from Allan variance analysis. The long-term stability measurements performed over 4 months, indicate that a maximum deviation less than 0.35 K on the noise temperature is obtained with this ACL.