Dual-mode trapezium-loop microstrip bandpass filter

A novel compact and simple microstrip trapezium loop bandpass filter structure using only one resonator is developed in this letter, the inequilaterally structure perturbs the fields of the resonator and excite degenerate modes.Without coupling gaps, the new filter can reduce uncertainty in fabrication. Simulated results agree well with measured results. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:840–841, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25074