Multilayer dual-mode dual-band filter using square loop resonators

In this paper, a multilayer dual-band dual-mode band pass filter based on square loop resonators is proposed, which allows independent tuning of both resonant frequencies and both pass band bandwidths. The filter is realized on two stacked Taconic CεR-10 substrates, where one resonator is positioned in the upper layer and other one in the middle layer between feed lines and the ground. Despite a similarity of resonators, the coupling and feeds locations in regards to resonators in the filter, they operate at different bands. The influence of different geometrical parameters on the filter performances is analyzed: size of perturbation elements, loops length, loops width and substrate thickness. The fabricated filter has two pass bands positioned at 2.49GHz and 3.55GHz with 3dB bandwidths equal to 80.3MHz and 69.8MHz, respectively. Currently, optimization is underway to precisely comply with IEEE WLAN 802.11 b/g and the IEEE WiMAX 802.16 standard frequencies (i.e. at 2.4GHz and 3.5GHz).