Abstract
This study presents a comprehensive investigation of the transmission characteristics and filtering performance of a tailored one-dimensional rectangular waveguide structure (1D-RWS). The research employs a combined analytical-numerical approach. The system is first modeled theoretically using the Green's function method (GFM) to elucidate the underlying physical mechanisms and then validated through rigorous finite element method (FEM) simulations. A key focus of the work is to explore the influence of critical geometric parameters, including resonator length, lateral position, and width, on the filter's spectral response. The results demonstrate that the transmission spectra and resonant frequencies are highly tunable, exhibiting phenomena such as resonant frequency shifts, critical coupling, and variations in bandwidth with geometric modifications. These findings confirm that the proposed 1D structure provides a versatile platform for controlling electromagnetic wave propagation. Consequently, this waveguide can be considered a bandpass filter for applications in the radio-frequency spectrum, offering a design principle for integrated radio-wave circuits and communication systems.