In this article, we developed a dual-band band-pass filter (DB-BPF) based on stepped impedance resonators (SIRs) using coupled feeding lines input and output ports. The developed filter allows the adjustment of the frequency and the bandwidth of the upper band (3.8 GHz) and the lower band (2.4 GHz). The transmission coefficients of the DB-BPF are improved by maximizing the coupling between the SIRs. Furthermore, the capability of the rejection band is increased and the insertion losses between the two pass-bands are reduced. The experimental results for the insertion loss (S 21 ) and the return loss (S 11 ) of the lower band (2.4 GHz) were1.0 and 2.0 dB, respectively while the insertion loss and return loss for the upper band (3.8 GHz) were 23 and 25 dB, respectively. The 3 dB fractional bandwidths obtained for both bands were about 200 MHz and four transmission zeros around the passband edges were created to improve the selectivity of the DB-BPF. The overall size of the DB-BPF was also reduced significantly.
In this article, the reduced size of the ultra‐wide band (UWB) band‐pass filter (BPF) with λg/4 short stubs using π‐type meander structure and folding short stubs is presented. The π‐type meander structure and folding short stubs are adopted instead of the λg/4 transmission line (TL) and λg/4 short stubs to reduce the size of the proposed BPF. The overall size of the new BPF is reduced by 72.5% over the conventional BPF and other filters. The measurement results of the insertion and return losses are 1.61 and 15.4 dB with a bandwidth of 125% (1.96‐9.20 GHz) at a center frequency of 5.8 GHz. The total size of the BPF is 5.13 × 5.36 mm2. It is applied to a coordinate intelligent transport system. The proposed BPF can be fabricated for semiconductors because of its planar structure.
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