Analysis of Coupling Effects to PCBs Inside Waveguide Using the Modified BLT Equation and Full-Wave Analysis

In this paper, the conventional Baum-Liu-Tesche (BLT) equation is modified to achieve S-parameters as outputs, and full-wave analysis data for partial structures are combined with the modified BLT equation to handle a multi-scale problem. Constructing of a topological network for waveguide structures is demonstrated considering propagating modes of the waveguide, to investigate huge waveguide structures such as missiles. Also, in the process of investigations, a coupling mechanism of printed circuit boards (PCBs) inside a waveguide is established. A missile is simplified into a rectangular waveguide, and inside compartments are assumed to be separated by metal plates having apertures. By investigating the coupling effects to PCBs placed in the waveguide with three cases, it is verified that the coupling mechanism is affected by frequency regions of incident fields, transmission characteristics of apertures, and the parallel-plate waveguide resonance characteristics of a target PCB itself. Each result from the modified BLT equation is compared to a graph by calculating the entire structure using full-wave analysis, showing excellent agreements and its validity. Also, time efficiency is observed from comparing the analysis time of the modified BLT equation and full-wave analysis.