A numerical short-open calibration technique is applied to deembedding of planar discontinuities with periodically perturbed nonuniform feed lines in the full-wave method of moments (MoM) algorithm. Different from the other deembedding techniques that are based on the assumption of uniform feed lines, this proposed technique exhibits an unparalleled capability on modeling of planar circuits with nonuniform feed lines. To demonstrate this feature, the open and gap discontinuities are modeled under periodically nonuniform feed configuration, and the effective per-unit-length transmission parameters of slow-wave and electromagnetic bandgap structures are extracted from the full-wave MoM simulation. Two periodically nonuniform microstrip-line resonator circuits are modeled and then confirmed by EM simulators and measurement.