Compact and narrowband LTCC filter using vertically stacked end-coupled resonators

A compact and narrowband low temperature co-fired ceramic (LTCC) bandpass filter (BPF) is proposed using vertically stacked half-wavelength end-coupled resonators. The multilayered end-coupled stripline resonators are stacked and buried into LTCC substrate for vertical end-coupling and size reduction. The coupling strength between adjacent resonators is adjustable by offsetting the intermediate ground layer. A narrowband fractional bandwidth (FBW) of 1.9% and a significant size reduction of 80% are achieved. Measurements agree with the simulation results well. Performance and size reduction comparisons and discussions are also implemented. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:86–89, 2017