Nicola De
Zanche1,2, Brodi Roberts, 1,2, B. Gino Fallone1,2
1Department of Medical Physics, Cross
Cancer Institute, Edmonton, Alberta, Canada; 2Department of
Oncology, University of Alberta, Edmonton, Alberta, Canada
Preamplifier
S parameters are known to vary with B0 field strength and orientation.
Variations in noise figure are also expected, but such data has not been
reported until now. Here we present the variation of noise figure of a
commercially available amplifier (MAR 8A+, Mini-Circuits, USA) at field
strengths up to 9.4 T. The method allows arbitrary noise source impedances
for complete noise parameter measurement, if desired. Variations in noise
source power (ENR) with applied field are prevented by locating the noise
source outside the field.