Design of Miniaturized Comb-line LTCC Bandpass Filter Based on Cross Coupling

This paper proposes a four-order bandpass filter with a center frequency of 2.58 GHz and a bandwidth of 2.43 to 2.73 GHz. The insertion loss is 1.21dB and the return loss is about 19.5 dB. The filter has a good selectivity by adding the cross-coupling between the resonators to generate transmission zero, with stopband suppression of 36.21dB at 0.85f<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> and 47.59dB at 1.15f<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf>. Based on Low- Temperature Co-fired Ceramics (LTCC) technology, the final size of the filter is 5mm×3.3mm×1mm, which has good passband performance in a small size.