High-Q band rejection filter by using U-slot DGS

This paper presents a new U-slot defected ground structure (DGS) in the microstrip line for the use in the design of high-Q band rejection filter. Compared to the conventional DGS, a U-slot DGS has a simple shape but the slope of its rejection characteristic is more steep. The Q factor of the band rejection property for the U-slot DGS increases when the distance between two slots in the U-shape decreases. By employing three cascaded U-slot DGSs, a high-Q band stop filter is designed and fabricated. Experimental results show that the Q factor of the band stop filter with three U-slot DGSs is 38.4.