In 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.

A hepta-band bandpass filter (HB-BPF) based on folded cross-loaded stepped impedance resonator (SIR) was investigated. A cross-loaded SIR microstrip structure was arranged to produce several transmission zeros. In order to reduce the filter size, a folded cross-loaded SIR was proposed. The HB-BPF was designed on FR4 microstrip substrate with ε r = 4.4, thickness h = 0.8 mm, and tan δ = 0.0265. This HB-BPF achieves transmission coefficients of 0.

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This simulation study involved the use of a QC-SSIR (quad cross-tub stepped impedance resonator) to examine the behavior and performance of the MW-BPF (multi-wideband band pass filter). To evaluate the performance of the proposed model, it was compared to the case of the conventional resonator. In the results, MW-BPF was found o exhibit a superior performance in terms of the ease of fabrication, good transmission coefficients, and a wider fractional bandwidth. For the filter structure analysis, this study incorporated the ABCD matrix, with the design of the MW-BPF also based on the FR4 microstrip. The experimental conditions and parameters were set in such a way that for the substrate, tan δ = 0.0265, thickness = 1.6 mm, and εr = 4.4, and thickness h = 1.6 mm. at 2.58 GHz, 1.71 GHz, and 0.81 GHz, the proposed QC-SSIR-based MW-BPF achieved transmission coefficients/fractional bandwidths of 1.93 dB/13.9%, 1.49 dB/18.7%, and 0.60 dB/49.3%, respectively. Relative to the filter size reduction, the FQC-SSIR (folded quad cross-tub impedance resonator) was incorporated. The resultant observations indicated a possibility of BPF size reduction up to 46%. Also, the proposed framework was found to yield (at 2.62, 1.80, and 0.82 GHz) 1.76 dB/12.5%, 1.21 dB/17.7%, and 0.57 dB/49.6% transmission coefficient/fractional bandwidths, respectively. It is also worth indicating that the filter employed LTE2600, WCDMA1800, and GSM800. Therefore, the model exhibited a good agreement, which was depicted by the comparison outcomes between the measured values and the simulated values. Hence, the proposed design was found to be valid and reliable.

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