Single-Layered SIW Post-Loaded Electric Coupling-Enhanced Structure and Its Filter Applications

A broadband post-loaded electric coupling structure in single-layered substrate integrated waveguide with enhanced coupling is proposed and investigated. The proposed structure can achieve the maximum electric coupling coefficient of more than 0.11. The effects of dimensional parameters on the electric coupling are studied by simulation. The proposed structure is verified by designing two bandpass filters, namely, a wideband fourth-order quasi-elliptic filter and a narrowband fourth-order quasi-elliptic filter. The measured results show that the designs are capable of providing the 12% bandwidth for the wideband fourth-order quasi-elliptic filter and the 3% bandwidth for the narrowband fourth-order quasi-elliptic filter at 5.8-GHz WiMax bands.