A Compact Multilayer Quad-Band Bandpass Filter with Coupled SIRs
for Multi-Standard Wireless Systems
Hassan Saad Abdullah and
Raaed Thaaban Hammed
In this paper, we propose a compact quad-band bandpass filter by using short-ended stepped-impedance resonators (SE-SIRs) and open-ended stepped-impedance resonators (OE-SIRs) in a hybrid structure. The proposed design uses the odd- and even-mode resonances of the two types of resonators to produce four independent passbands in a compact multilayer structure. The first and second passbands are set by SE-SIR resonators at 1.56 and 2.5\,GHz, respectively. The third and fourth passbands are centered at 3.5 and 5.2\,GHz, respectively, due to the OE-SIR resonators. To achieve the quad-band response in a compact size, a multilayer arrangement with electromagnetic broadside coupling between the feeding structure and resonators has been adopted. Finally, the filter is designed, simulated, fabricated, and measured using a Rogers-Ceramic RO4360 substrate with a permittivity of εr = 6.15 and thicknesses of (h1 = 0.3, h2 = 0.508) mm. Simulated insertion losses were 0.29, 0.26, 0.43, and 0.66 dB, and return losses were 28.65, 15.05, 14.04, and 17.3 dB in each of the four operating bands, respectively. Filter responses from simulation and measurement are contrasted and discussed. The produced filter is very small, covering a circuit area of about 129 mm2, without feeding ports.
