Sharp roll‐off triband microstrip bandpass filter with wide stopband for multiband wireless communication systems

Design of a novel triband bandpass filter is presented for wireless communications systems. The based on inter-coupled stepped impedance resonators and inter-digitally coupled to the input/output ports. configuration circuit consists open-loop that are electromagnetically each other using inverted T-shaped open stubs. intrinsic characteristics structure generates five transmission zeros results in response exhibiting sharp selectivity, high inter-band isolation wide out band rejection. Unlike filters reported recently literature proposed single layer does not require any short-circuited plated through hole which can introduce fabrication complexity therefore production costs. Moreover, be configured provide passbands with identical 3-dB fractional bandwidth whose center frequency equally spaced. In prototype design here passband frequencies set 3.6, 4.6, 5.6 GHz corresponds WiMAX, 5G, WLAN applications. consequence employing open-circuited lines relatively large structure, overcome by higher dielectric constant substrate. was designed achieve 11.9%. Measured confirm better than 30-dB. theoretical model consistent measured results.