Bandpass compact microstrip filters for wireless communication

It was established that the coupling coefficient of two neighbouring microstrip resonators (separated by a narrow clearance) could be successfully controlled by the openings in the resonator electrodes. The openings are located near the short-circuited part of the quarter-wave resonators and decrease their coupling coefficient. Based on these resonators, a new compact microstrip filter with a narrow bandpass (less than 1%) were realized.