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

Riaz, Muhammad, Virdee, Bal Singh, Mariyanayagam, Dion, Salekzamankhani, Shahram, Benetatos, Harry and Lubangakene, Innocent (2022) Sharp roll-off triband microstrip bandpass filter with wide stopband for multiband wireless communication systems. International Journal of RF and Microwave Computer-Aided Engineering, 32 (12). pp. 1-10. ISSN 1096-4290


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

Int-J-RF-Mic-Comp-Aid-Eng_2022_Riaz_Sharp-roll‐off-triband-microstrip-bandpass-filter-with-wide-stopband.pdf - Published Version
Available under License Creative Commons Attribution Non-commercial No Derivatives 4.0.

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