Applying of Koch island fractal in Hi-Lo impedance line low-pass filter

In this paper, hi-lo impedance line low-pass filters with different Koch island fractals are presented. Comparing with the traditional hi-lo impedance line low-pass filter, the fractal structure will weaken current discontinuity, so the pass band return loss is reduced, the pass band performance of the low-pass filter is enhanced. It can also reduce filter size and improve restraint outside the band. The different of Koch island fractal will lead to differences in the improvement of pass band return loss. The simulation result shows that the maximum value of the pass band return loss is reduced from -16.6dB to 20.3dB and 22.2dB.