Compact Coupled Line Based Multiband Bandpass Filter

Multiband Band pass filters play a critical role in wireless communication systems, as they enable the recovery of specific bands of signals in wireless receiver applications while rejecting unwanted signals. In real-life handheld device applications, there is a need to allow multiple bands of frequencies simultaneously. This paper focuses the design of a compact multi-band bandpass filter using multi coupled microstrip transmission lines. The filter was designed using open circuited stubs resulting in a more compact implementation. Three sets of resonators were used (A1/A2), (B1/B2), (C1/C2) respectively to provide three different passbands with independency. The design was simulated using Advanced design system 2022 software. The filter resonates at the center frequencies of 2.45 GHz in the unlicensed ISM band, 3.55 GHz in the 4G band and 5 GHz in high-speed Wi-Fi band. The designed filter exhibited low insertion loss, high return loss, a fast and smooth transition from passband to stopband, a better bandwidth response, with smaller physical dimension.