Coupled filter design covers the odd and even wave coupling of transmission lines, which results in odd and even characteristic line impedances. Cascading the parallel coupled-line sections gives rise to bandpass filter structures. Since conventional coupled-line filter is large in size, it is not suitable for wireless communications. Hairpincomb and zig-zag filters were introduced to solve this disadvantage. These filters have narrow-band and compact size. This paper focuses on designing hairpin-comb and zig-zag filters at 1800 MHz and comparing their performances. The results show that a hairpin-comb microstrip filter has a better performance than a zig-zag microstrip filter in three categories, namely, return loss, size, and passband bandwidth.
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