TWIN-HORSESHOE RESONATOR - AN INVESTIGATION

Two parallel-plate copper rings with diagonally opposite gaps separate d by a dielectric medium form a resonator the natural resonant frequen cy which is a function of the transmission line propagation constant, its characteristic impedance, as well as the series inductance of the two loops. By means of an extra capacitor connected to each gap, one c an easily vary the frequency of the resonator. The derived expressions , valid also for coaxial line devices, relating resonant frequency to other circuit constants, can serve as a tool for those who intend to u se this kind of resonator to design NMR surface coil antennas. Experim ental results are in good agreement with theory provided the circuit c onstants are accurately known.