Abstract
Different noise sources in HEMTs are discussed, and state-of-the-art
low-noise amplifiers based on the Fraunhofer IAF 100 nm and 50 nm
gate length metamorphic HEMT (mHEMT) process are presented. These
mHEMT technology feature an extrinsic fT of 220 / 375 GHz and an
extrinsic transconduction gm, max of 1300 / 1800 mS/mm. By using
the 50 nm technology several low-noise amplifier MMICs were realized.
A small signal gain of 21 dB and a noise figure of 1.9 dB was measured
in the frequency range between 80 and 100 GHz at ambient temperature.
To investigate the low temperature behaviour of the 100 nm technology,
single 4 * 40 um mHEMTs were integrated in hybrid 4 - 8 GHz (Chalmers)
and 16 - 26 GHz (Yebes) amplifiers. At cryogenic temperatures noise
temperatures of 3 K at 5 GHz and 12 K at 22 GHz were achieved.
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