A N77 band bandpass filter for 5G applications using LTCC technology with wide upper stopband

Abstract A bandpass filter (BPF) designed for the 5G N77 band using low-temperature co-fired ceramic (LTCC) technology is presented in this paper. This proposed BPF incorporates a pair of hook-shaped microstrip feeding lines (HSMFLs) on the top layer and a T-junction resonator on the second layer. In order to realize a wider upper stopband, the HSMFL is composed of a stepped-impedance variation microstrip line (SIVML) and a folded microstrip line with enhanced coupling effect at the end. With a compact structure measuring 26.85 × 12.68 × 0.20 mm 3 , which equates to 0.689 × 0.325 × 0.005 λ g 3 , the design achieves an exceptional performance profile. The proposed BPF demonstrates superior performance with an out-of-band suppression higher than 20 dB up to 3.35 f 0 , while maintaining low in-band insertion loss (IL) under 0.3 dB. The proposed BPF offers significant potential for 5G mobile communications due to its wide upper stopband, exceptional out-of-band suppression capability, low in-band IL, simple design, and compact structure.