Low Noise Amplifiers at 67 – 116 GHz

The research of the Advanced Radio Instrumentation Group (ARIG) is focused on the design and development of low noise amplifiers (LNAs) and front-end receiver instrumentation, primarily for use in astronomical instrumentation, often operating at cryogenic temperatures to minimise their noise contribution. Advances in materials, design and fabrication technology has now allowed LNAs to become competitive with other technologies, such as SIS mixers, at frequencies beyond 100 GHz. Through the ALMA Band 2+3 project we have shown that recent technological developments in cryogenic monolithic microwave integrated circuit (MMIC) high electron mobility transistor (HEMT) amplifiers provide an opportunity to extend the originally planned onsky bandwidth, combining ALMA Bands 2 and 3 into one receiver cartridge covering 67-116 GHz. We will discuss the recent advancements in our ALMA 2+3 LNAs, both MMICs and packaged LNAs using stateof-the-art technology. The packaged LNAs have been characterised at room temperature and cryogenic ambient temperature of 20 K for S-parameter and noise performance. We will also show recent developments in MMIC designs with measured optimum performance around 80 GHz.