Characterization of Narrowband Hairpin Bandpass Filter Composed of Fractal Koch Geometry

In this paper, a narrowband hairpin bandpass filter (BPF) composed of fractal Koch geometry is characterized numerically and experimentally. The implementation of fractal Koch geometry aims to minimize the dimension of filter which aspects to reduce the need of material. The filter which utilizes the 1st iteration of fractal Koch geometry, later referred as fractal hairpin BPF is established using 7 elements deployed on a Rogers RO4350 dielectric substrate with the thickness of 1.52 mm. Prior to hardware realization, the proposed filter is numerically characterized to deal with the required specification. The filter which is intended for radar application is designed to have center frequency of 3 GHz with the 3 dB minimum working bandwidth of 200 MHz. It is shown that the realized fractal hairpin BPF which has the dimension of 16mm x 47mm and is approximately 20% smaller than the dimension of conventional one demonstrates the 3 dB working bandwidth of 260MHz with the center frequency of 3.01 GHz.