Design of Quad-Band Filter Based on the Improved Versions of Dcrlh Cell

In this article, one realization version of quad-band filter is firstly proposed, and it is the cascaded structure composed of the shunt open-circuit DCRLH (dual composite right/left-handed) cell and the shunt short-circuit DCRLH cell. The above two cells are initially proposed here in order to improve the inherent limitations of the microstrip DCRLH cell. It is demonstrated that the matching performance and frequency selectivity of these two cells are both better than those of the microstrip DCRLH cell. What is more important, these two cells both exhibit three transmission zeros within the given frequency band and any of them is of great potential to be applied in the design of quad-band filters. In order to get sufficient design freedom, we utilize the cascade connection version based on the shunt open/short-circuit DCRLH cells. Whereas, only the first and second transmission zeros of both the shunt open/short-circuit DCRLH cells are explored. Both the simulated and measured results indicate that the proposed design method is right and effective.