MATCHING RF COILS FOR NMR TOMOGRAPH
Peter Andris
The RF coil of an NMR tomograph in an RF magnetic field created by
precessing protons induces electrical voltage or vice versa, the electrical
current flowing throuhg the coil causes an RF magnetic field influencing
on protons in the sample. Circuits consisting of capacitors together with
the coil can be tuned to resonance and their impedance can be matched
to the characteristic impedance of the transmission line to achieve
lossless transfer of electrical power. The paper presents equations for
the calculation of elements of two different matching circuits and
for the calculation of their output impedance which can be considered as
a good tool for judging the quality of matching. The qualities of the
circuits have been discussed.
Keywords: coil matching, tuning, balancing, impedance
|