Simplified Design Procedure for Fourth-Order Coupled-Resonator Bandpass Filter

This paper presents a new simplified procedure to design a fourth-order coupled resonator filter. This procedure does not require the calculation of complicated Eigenvalues to develop the required coupling matrix. It starts with studying the effects of different coupling mechanisms on the performance of the overall filter structure. Then, these coupling mechanisms are combined to obtain the design of the required filter. This procedure may be more suitable for machine learning procedure to design coupled-resonator filters. The proposed method is used to design a substrate integrated waveguide (SIW) bandpass filter for sub-six GHz 5G applications. The designed SIW bandpass filter operates in the frequency range from 3.7 GHz to 3.98 GHz which covers the New C-band 5G network with a fractional bandwidth (FBW) of 28% and is centered at 3.84 GHz. This filter is fabricated and measured for verification.