Miniaturized microwave modified Koch fractal Hairpin Filter with harmonic suppression

Designing a filter with harmonic suppression capability without adding any external filtering capacitors or notch filter is a big challenge. The paper presents the design of a compact microstrip bandpass filter having integrated harmonic suppression capability. The filter operates at a center frequency of 900 MHz. The structure chosen is the Hairpin Filter. The conventional hairpin is modified by integrating with Koch fractal shaped structure for miniaturisation and harmonic suppression capability. The filters were simulated and optimized using electromagnetic simulation software. Integration of fractal shaped structure into microstrip filters can be used as harmonic suppressor. In addition, reduction in size is also attainable. Second harmonic suppression of up to -35 dB is achieved for the fractal shaped Hairpin Filter, FSF, design.