Wideband cryogenic LNA design for the ngVLA band-1 receiver

The next-generation Very Large Array (ngVLA) front end incorporates six dual-polarization receivers covering the frequency range from 1.2 to 116 GHz. The ngVLA Band-1 receiver covers a frequency range of 1.2 to 3.5 GHz. This wideband requirement presents a challenge for the extremely low noise design for the required cryogenic low noise amplifier (LNA). GaAs HEMT technology is very reliable at a gate length of 150 nm and that gate feature size is suitable for low noise amplifiers up to the microwave frequency range. Below 3 GHz, the transistor gate has a very large capacitive impedance, exhibiting like an open circuit, which requires large values of inductors for 50 Omega impedance and low noise matching. The hybrid circuit configuration allows the design to select high-Q discrete inductors and capacitors with large values to minimize loss/noise from passive components. A two-stage single-ended GaAs HEMT LNA was designed based on the hybrid configuration. A prototype ngVLA Band-1 LNA was assembled and fully tested at a physical temperature 12 K. This newly designed GaAs HEMT LNA achieved 1.6 K average noise temperature and 34 dB average high gain between 1.2 and 3.5 GHz, the total power consumption is about 10 mW, which can meet the current requirements of the ngVLA Band-1 receiver.