Current research considers the crossbar H-mode linear resonant accelerator with drift tubes mounted inside the cavity. The focus of the study has been on the dependence of resonant frequency on the parameters of the geometry. Since Alternating-Phase-Focusing (APF) type of accelerator is investigated, the efficiency of the operation depends on the synchronization of the charged particle velocity and accelerating field oscillations. Researchers can control it by the variation of longitudinal size of the cells of the structure (periods). On the other hand, the effective performance of this resonant system requires the equality of resonant frequencies of its cells, because it affects the uniformity of accelerating field distribution along the axis. The diversity of cells longitudinal sizes causes the deviation from the particular value of the resonant frequency. This aberration can be eliminated by the adjustment of other geometry parameters period's length, gap length and drift tube radii. We have conducted the study to analyze the relation between resonant frequency and these values. Using the this dependency we can tune the geometry parameters of each period in the structure. We first create the computer-aided design (CAD) geometry model of the accelerator cavity. Then, using Comsol Multiphysics, the platform for physics-based modeling and simulation, we conduct the calculation of resonant frequencies.