Parallel-plate split-conductor surface coil: analysis and design

A split-conductor circular parallel-plate resonator with one end shorted to ground can be used to one's advantage as a surface coil for NMR imaging experiments. It can be easily constructed by a printed-circuit method and possesses a relatively high loaded Q with negligible frequency detuning. From the proposed equivalent circuit, an equation was derived that relates the self-resonance frequency of the resonator to the split distance measured from a reference point. An example of a 101-mm-diameter surface coil operating at 26 MHz for 31P in vivo spectroscopy is given to illustrate the concordance between calculated and experimental results. Complementary equations and formulas are also included to assist researchers in designing their own antennas to meet specific requirements.