Development of MM-Wave Transistor Amplifiers for Focal Plane Arrays

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These funds support a three year effort to develop low-noise cryogenic transistor amplifiers for use in millimeter wavelength radio astronomy. Transistor amplifiers offer a number of significant advantages for radio astronomical systems, including very low (Tn 65 K SSB) noise, large (10 - 20 GHz) instantaneous bandwidth, single sideband system operation without input filters, and good stability. There are additional virtues of particular importance for focal plane array systems. Such systems are relatively non-critical in terms of operating temperature and other conditions and they are well-adapted to reproduction in the quantities required for arrays. No mechanical adjustments are required for optimum performance. Projections for the performance of HEMT amplifiers in the 3 mm band are receiver noise temperatures below 65 K (single sideband), which should yield atmospheric- limited performance at most frequencies. The large bandwidth will facilitate searches for multiple spectral lines over a large frequency range as well as for emission from galaxies having unknown velocities. Presently available devices offer extremely low noise performance in the 40 - 50 GHz range, which is where initial efforts will be directed. Within two years, devices with comparable performance in the 3 mm wavelength range should be obtainable.