[asac][almanews] ALMA Memos 421 Released

[Stacy Oliver]

ALMA MEMO #421

GaAs-BASED CRYOGENIC AMPLIFIER FOR ALMA 2SB MIXER

Christophe Risacher and Victor Belitsky
Onsala Space Observatory, Sweden

2002/04/18

Keywords: Cryogenic LNA, GaAs HEMT, InP HEMT, 2SB SIS mixer

As part of Onsala Space Observatory instrumentation activities, a 4-8 GHz
cryogenic low-noise amplifier was developed. This 2-stage LNA demonstrates
26 dB gain with noise temperature of 5.0 K using commercial GaAs transistors
MGFC4419G from Mitsubishi. The total power consumption is of about 12 mW
while with a total power consumption tuned down to 4 mW, the gain drops to
24 dB and the noise is of 6.0 K. This performance is in a very good
agreement with simulations and believed to be among the best-reported using
GaAs transistors. The amplifier design was carried using Agilent ADS, HFSS
and Momentum CAD software. This amplifier will be used as a cold IF
amplifier for mm and sub-mm wave receivers with SIS and HEB mixer, primarily
for APEX Project as well in our development of ALMA band 7 sideband
separation mixer providing two independent IF channels (USB and LSB) of 4-8
GHz, therefore fulfilling the 8 GHz bandwidth requirements for ALMA. In this
paper we present details on the amplifier design, performances (modelled and
measured) and gain-stability comparison between GaAs and InP transistor
based amplifiers.

View a pdf version of ALMA Memo #421.
http://www.alma.nrao.edu/memos/html-memos/alma421/memo421.pdf

Download a postscript version of ALMA Memo #421.
http://www.alma.nrao.edu/memos/html-memos/alma421/memo421.ps


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