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.