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

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