Design of Low-Loss Six-Channel Multiplexer with Metal Integrated Suspended Line Hybrid Resonators

This work presents a miniaturized low-loss six-channel multiplexer for sub-6 GHz communications based on metal integrated suspended line (MISL) technology. Unlike conventional multiplexers that rely on multiple single-channel filters combined through a manifold or T-junction, the proposed design employs two triple-band filters realized using patch bandpass resonators and half-wavelength bandstop resonators. The two triple-band filters are combined in a diplexer architecture to achieve a six-channel response, significantly simplifying the overall topology while maintaining compact size and low insertion loss. Each triple-band filter is synthesized by coupling half-wavelength bandstop resonators with patch bandpass resonators, creating multiple passbands with controllable transmission zeros. A prototype was designed, fabricated, and measured. The measured results show good agreement with the theoretical predictions, validating the proposed multiband diplexer architecture as an effective solution for integrated multiband front-end modules.