In this paper we present electromagnetic (EM) analysis of the unloaded slotted-tube resonator (STR) with a circular cross section, using the finite element method (FEM) and method of moments (MoM) in two dimensions. This analysis allows the determination of the primary parameters: [L] and [C] matrices, optimization of the field homogeneity, and simulates the frequency response of S(11) at the RF port of the designed STR. The optimum configuration is presented, taking into account the effect of the thickness of the STR and the effect of the RF shield. As an application, we present the design results of a MRI probe using the STR and operating at 500 MHz (proton imaging at 11.74 T). The resonator has -69.37 dB minimum reflection and an unloaded quality factor (Q(o)) > 500 at 500 MHz.

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In this paper, we have implemented a numerical tool using finite element method (FEM) for designing an antenna for MRI (Magnetic Resonance Imaging) probe operating at high field. The birdcage antenna type is a transverse electromagnetic (TEM) coupled lines resonator, and the developed model in the absence of a biological load is based on the propagation equations of voltages and currents on the coupled lines of the resonator. This numerical tool simulates the frequency response of the reflection coefficient of the RF (Radio Frequency) excitation port of the resonator, which allows us to estimate the level of adaptation of the antenna for imaging small animals at a field of 9.4 T.

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