Engineering topics

Smith, Phillip M.

Publications and source records attributed to Smith, Phillip M..

3 records

NASA NTRS1989

32-GHz cryogenically cooled HEMT low-noise amplifiers

The cryogenic noise temperature performance of a two-stage and a three-stage 32 GHz high electron mobility transistor (HEMT) amplifier was evaluated. The amplifiers employ 0.25 micrometer conventional AlGaAs/GaAs HEMT devices, hybrid matching input and output microstrip circuits, and a cryogenically stable dc biasing network. The noise temperature measurements were performed in the frequency range of 31 to 33 GHz over a physical temperature range of 300 K down to 12 K. Across the measurement band, the amplifiers displayed a broadband response, and the noise temperature was observed to decrease by a factor of 10 in cooling from 300 to 15 K. The lowest noise temperature measured for the two-stage amplifier at 32 GHz was 35 K with an associated gain of 16.5 dB, while the three-stage amplifier measured 39 K with an associated gain of 26 dB. It was further observed that both amplifiers were insensitive to light.

Duh, K. H. George↗

NASA NTRS1988

High-performance Ka-band and V-band HEMT low-noise amplifiers

Quarter-micron-gate-length high-electron-mobility transistors (HEMTs) have exhibited state-of-the-art low-noise performance at millimeter-wave frequencies, with minimum noise figures of 1.2 dB at 32 GHz and 1.8 dB at 60 GHz. At Ka-band, two-stage and three-stage HEMT low noise amplifiers have demonstrated noise figures of 1.7 and 1.9 dB, respectively, with associated gains of 17.0 and 24.0 dB at 32 GHz. At V-band, two stage and three-stage HEMT amplifiers yielded noise figures of 3.2 and 3.6 dB, respectively, with associated gains of 12.7 and 20.0 dB at 60 GHz. The 1-dB-gain compression point of all the amplifiers is greater than +6 dBm. The results clearly show the potential of short-gate-length HEMTs for high-performance millimeter-wave receiver applications.

Duh, K. H. George↗

NASA NTRS1986

Noise parameters and light sensitivity of low-noise high-electron-mobility transistors at 300 and 12.5 K

The four noise parameters of cryogenically cooled HEMTs have been investigated. Two different HEMT structures, with and without a spacer layer, were tested. The noise parameters of both structures were similar at room temperature, while they were dramatically different at cryogenic temperatures. The minimum noise temperatures measured at 8.4 GHz were 75 + or 5 K at room temperature and 8.5 + or - 1.5 K at the temperature of 12.5 K. The cryogenic performance is the best ever observed for field-effect transistors.

Pospieszalski, Marian W.↗