In this work, we apply the method of modal parameters for investigation of SEM poles of open-circuit wires. The main accent is done for investigations of pieces of symmetrical wire structures: a straight finite wire in free space, a straight finite wire parallel to a PEC ground, a circle arc and a helix segment. The symmetry of these structures allows a fast calculation of matrix elements in the MoMP, especially for the straight wire where one can obtain explicit analytical result and investigate poles of high layers. The investigation has shown that the real part of the SEM poles for a finite straight wire in free space, a finite straight wire above a ground plane and a circular arc wire increases monotonically with increasing the number of the pole. In contrast, for a large segment of the helix wire, a more complex dependence of the real part of the SEM pole on its number n is observed. This is due to the fact that for some numbers n of the pole there are effective common modes of the current, which corresponds to strong radiation and a large real part of the SEM poles, and for some $n$ there are effective differential modes, which corresponds to weak radiation and a small real part of the SEM poles.
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