Abstract #1820
Prediction of RF Preamplifier Noise Temperature Variations in a Magnetic Field
Cameron M. Hough 1 , Russell L. Lagore 2 , Cecilia Possanzini 3 , and Nicola De Zanche 1
1
Department of Oncology, University of
Alberta, Edmonton, Alberta, Canada,
2
Center
for Magnetic Resonance Research, University of
Minnesota, Minneapolis, Minnesota, United States,
3
Philips
Healthcare, Best, Netherlands
In this work we investigate the noise temperature
variations of RF preamplifiers when exposed to an
external magnetic field. The noise parameters are
expressed in terms of the transconductance which varies
with the magnetic field and is readily derived from
S
parameters
measured using a network analyzer. Models for
field-effect transistors and bipolar-junction
transistors were applied and fitted to measured noise
temperature data. Noise parameter changes as a function
of B
0
are
calculated.
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