Dual‐wideband band pass filter using folded cross‐stub stepped impedance resonator

Abstract

AbstractIn this letter, a dual‐wideband band pass filter (DW‐BPF) using cross‐stub stepped impedance resonator (CS‐SIR) was simulated, fabricated, and measured accordingly. The CS‐SIR was used to replace the conventional half‐wavelength open stub resonators. Compare to the conventional resonator, the CS‐SIR resonator has a wider fractional bandwidth and ease of fabrication. Furthermore, the DB‐BPF was fabricated on microstrip with ɛr = 4.4, h = 0.8 mm, and tan δ = 0.0265. The DW‐BPF with CS‐SIR achieves transmission‐coefficients/fractional‐bandwidth of 0.22 dB/94.19% and 1.87 dB/33.52% at 1.14 GHz and 2.31 GHz, respectively. In order to reduce the filter size, a folded CS‐SIR (FCS‐SIR) was also proposed. As a result, this BPF size was reduced to 53%, with the BPF size of 0.30 λG2 and 0.14 λG2 for DW‐BPF with CS‐SIR and DW‐BPF with folded CS‐SIR, respectively. The λG is the wavelength at the first frequency. Further, the DW‐BPF with FCS‐SIR achieves transmission coefficients/fractional bandwidth of 0.19 dB/89.08% and 1.29 dB/31.90% at 1.21 GHz and 2.41 GHz, respectively. Measured results are in a very good agreement with the simulated results.