A Compact Tunable Triple Stop-Band Filter Based on Different Defected Microstrip Structures

A compact triple stop-band filter based on different defected microstrip structures is proposed, fabricated and measured to filter out the undesired narrowband signal interferences against UWB systems. A meander line slot (MLS), a U-shaped slot (USS) and a spur line (SL) are etched on a 50-Ohm microstrip line to achieve the expected triple stop-band function and to provide a good tunable characteristic by selecting the proper dimensions of the MLS, USS and SL. The equivalent circuit model and its simulations are presented to evaluate the designed triple stop-band filter. Simulated and measured results are given to demonstrate that the proposed triple stop-band filter has controllable center frequencies and compact size.