[Legacy Report] ULTRA-LOW-NOISE, InP FIELD EFFECT TRANSISTOR RADIO ASTRONOMY RECEIVERS: STATE-OF-THE-ART

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In the early 1970's, the ultra-low-noise receiving systems employed mainly solid-state masers, cryogenically-cooled parametric amplifiers (or converters) and Schottky diode mixers. At the end of that decade, advances in GaAs FET technology, combined with cryogenic cooling, made the noise performance of GaAs FET amplifiers competitive with the noise performance of parametric amplifiers and masers. Indeed, improvements in the noise temperature of field-effect transistors (FET’s) and, later, heterostructure field-effect transistors (HFET’s) over the last several decades have been quite dramatic. In 1970, a noise temperature of 120 K was reported at 1 GHz and physical temperature of 77 K; in 2003, noise temperatures of 2, 8 and at 35 K were reported at 4, 30 and 100 GHz, respectively, for physical temperatures of 14 to 20 K. These last results were achieved with InP HFETs. Broadband amplifiers using these devices have been successfully used in a number of instruments for radio astronomy research. These include: Very Large Array (VLA), Very Large Baseline Array (VLBA), Green Bank Telescope (GBT), Wilkinson Microwave Anisotropy Probe (MAP), Planck Low Frequency Instrument and several ground-based instruments for the investigation of cosmic microwave background. Against this background, the presentation will focus on the following main topics:


Noise models of microwave transistors and their general properties common to all field effect (FET) and bipolar transistors (BT)
Noise and signal properties of InP heterostructure field effect transistors (HFETs) at cryogenic temperatures
Design and examples of realizations of wideband, low-noise, cryogenically-coolable HFET amplifiers in 1 to 115 GHz range
Examples of realizations of receivers for interferometric arrays
Examples of realization of very broadband continuum radiometers

In conclusion, thoughts on future developments in low-noise amplifier technology will be offered. Especially a question whether rapidly advancing technologies of microwave heterostucture bipolar transistors (HBT’s) and CMOS can in the future offer alternatives to the extremely low noise performance of InP HFET’s will be addressed.

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