Design of a Compact Dual-Band Microstrip Bandstop Filter with High Rejection Levels

In this paper, a novel compact dual-band microstrip bandstop filter with third order Chebyshev filtering function is presented. Meandered open-circuited stubs and meandered transmission lines are used to design the proposed filter within a compact circuit size. Both stopbands can be independently controlled with respect to the changes in the open-circuited stubs. The designed filter with the center frequencies of 1.13 and 3.47 GHz with the 3-dB fractional bandwidths of 46.4 % and 15.3 % was fabricated and measured to validate the proposed model. The measured results exhibit an excellent agreement with the simulated ones. Rejection levels at both stopbands have been measured as better than 29 dB.