Design of Dual-Band Band-Pass Filters with Compact Resonators and Modern Feeding Structure for Wireless Communication Applications

Abstract

In this paper two new planar dual-band band-pass filters (DBBPF), that each of them is designed using an exclusive type of feed structure and by planar technologies of microstrip have been presented. First DBBPF is implemented, using compact open-loop meandering resonators, and open stub-loaded feed-lines. The cause of introducing the transmission zeros near the pass-bands of the first filter is source/load coupling at stub-loaded feed structures. The longer resonators, which are fed by open-stub loaded feed-lines, independently control the lower pass-band and the shorter resonators which are magnetically coupled, independently control the higher pass-band. The second DBBPF are designed by using 0° feed structure and by combining of two types of resonators. The main resonators with diagonal feeding structure and similar to stepped-impedance resonators (SIR) construct the lower pass-band. The sub-resonators with double-spiral and inter-coupling, can be embedded in the structure of main-resonators and construct the higher pass-band. There is a cross-coupling between the four sub-resonators, that suppresses any harmonics and introduces the extra transmission zeros at each side of second pass-band. Both sets of DBBPFs are designed to miniaturize, improve the gain, decrease losses and are fabricated to apply to wireless communication applications. The obtained experimental results validate the simulation results.