Wide Stopband Bandpass Filter for 5G N79 Band Applications

ABSTRACT A compact bandpass filter (BPF) with a wide stopband is proposed for the fifth‐generation (5G) mobile communication N79 band applications. The proposed BPF is symmetrically constructed of a pair of L‐shaped microstrip feeding lines (LSMFLs) and a T‐shaped resonator. For a wide stopband, the LSMFL is constructed of a stepped‐impedance variation (SIV) structure and a folded microstrip line with enhanced coupling effect. Fabricated on a two‐layer low‐temperature co‐fired ceramic (LTCC) substrate, the proposed BPF has a compact size of 22.76 × 10.97 × 0.20 mm³ (i.e., 0.732 × 0.352 × 0.006 λ g ³). A measured in‐band insertion loss (IL) better than 0.3 dB and a wide stopband up to 3.5 f 0 with a high suppression level of 20 dB are both achieved.