A frequency selective limiter (FSL) is provided having a transmission line structure with a tapered width. The FSL includes a substrate having a magnetic material, a signal (or center) conductor disposed on the substrate and first and second ground plane conductors disposed on the substrate. The signal conductor having a first end with a first width and a second end with a second different width such that the signal conductor is provided having a taper between the first and second ends of the signal conductor. First and second ground plane conductors are spaced apart from first and second edges of signal conductor, respectively, by a distance that changes from the first end of signal conductor to the second end of signal conductor such that signal conductor, and first and second ground plane conductors form a co-planar waveguide transmission line.