Folded Substrate Integrated Waveguide Engineering Applications

Folded substrate-integrated waveguide is a novel planar transmission line, which is an improvement of substrate integrated waveguide (SIW). The height of FSIW is twice of that of SIW, while the width of FSIW is only half of SIW, leading to more compact structure, meanwhile, it nearly keeps all the transmission characteristics of SIW. With such good advantages, its wide engineering applications can be expected in the near future.We have already finished the theoretical investigation on FSIW, including the formula derivation such as propagation constant and cutoff frequency etc. However, the engineering application has not been found too much. In this way, the engineering application of FSIW will be investigated in our work. Firstly, the effects of cylinder spacing on characteristics of SIW have been addressed; some conclusions can be obtained from the HFSS simulations. In succession, the FSIW resonant cavity has been investigated, the formulas of resonance frequency and quality factor are derived, and the verifications at several frequency bands have been made. Lastly, two FSIW devices—resonator band pass filter based on FSIW and 3dB directional coupler, are proposed and designed to demonstrate the engineering application of FSIW structure. In the design of resonator band pass filter based on FSIW, the band pass characteristic is achieved through the coupling between resonators etched on the middle metal plane, and the measured and simulated results are in good agreement. As to 3dB directional couplers, two 3dB directional couplers with single slot and double slots are designed and simulated, demonstrating good performances.