A Novel Concept in Design of Microwave Planar Dual Band Filter having the Controllable Closed/Isolated Bands by Using the Simple Vias and the Slow Wave Effect for 5G/IoT Applications

A microstrip dual-mode dual-band bandpass filter with slow wave effect is presented in this paper. The slow wave effect is provided by interdigital unit cells. The interdigital unit cell located into microstrip resonator is investigated using full-wave electromagnetic simulations. It is shown that an extra surface area is not required to obtain the slow wave effect using these resonators. Using of metal vias on the resonator allows to be designing a dual-band bandpass filter configuration with out-of-band rejection characteristic. The proposed filter exhibits a wideband frequency response since the I/O ports are directly connected to the resonator. Both simulated and measured results are presented to demonstrate the proposed filter.