This paper presents an application of cavity modeling technique to study its effectiveness in analyzing complex waveguide networks, like a five-port four-hole dual-side backward coupler. The proposed structure has been modelled using four waveguide sections, including a square waveguide, and forty-four cavities. The modeling resulted fifty-three interfacing apertures, which required total one hundred six simultaneous matrix equations to be solved. The matrix equations have been solved using method of moments to find field distributions at the apertures between different regions and frequency response of the structure. The analysis has been verified by comparing numerically calculated data with literature available data.