Quad-band bandstop filter modeled by comprising quad-section stepped-impedance resonator
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This paper presents the implementation of symmetric folded meandered-line structure that includes a quad-section stepped impedance resonator (QSIR). The existence of four stop bands at 1.81/5.16/8.08/10.90 GHz was successfully synthesized by the incorporation of QSIR comprising an electrical length of 0.84λg–0.19λg–0.15λg–0.22λg. The throughput of the filter was further improved by the inclusion of five attenuation poles at 340 MHz, 3.24, 6.38, 9.45, and 11.92 GHz with the rejection levels of − 32.19, − 25.19, − 28.68, − 21.57, − 32.63 dB, respectively. The concept achieves a wide fractional bandwidth of 59/18.23/13.86/10.46% at 1.81/5.16/8.08/10.90 GHz, respectively. Noticeable attenuation of − 25 dB at the respective stop bands in the frequency range of 2.34–1.28, 5.60–4.66, 8.56–7.44, and 11.35–10.21 GHz, with a spurious-free response up to 13 GHz was confirmed. Furthermore, a sharp response is demonstrated by a simulation and shows strong agreement with the measurement results.
KeywordsBandstop filter (BSF) Symmetric meandered-line Quad-band Quad-section Stepped-impedance resonator (SIR)
This research was supported by the National Research Foundation of Korea (NRF) Grant funded by the Korea Government (MISP) (2016R1A4A1011761). The part of this research was also supported by the research Grant of Sejong University in 2018.
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