Compact ultra‐wideband bandpass filter with improved out‐of‐band rejection

This letter presents a compact ultra-wideband bandpass filter with improved out-of-band rejection performances. Complementary split ring resonators with microstrip feed lines are used to design the filter. Measurements show that maximum insertion loss within the ultra-wide passband is below 2 dB. The 50-dB stopband on the lower end is from DC to 2.48 GHz and the 25-dB upper stopband is from 11.27 to 20 GHz. Out-of-band rejection performance of the filter satisfies and exceeds the U.S. Federal Communications Commission's indoor limit. Implementation area of the filter is 0.54 λg × 0.22 λg, λg is the guided wavelength of 50-Ω microstrip line at 6.85 GHz. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 758–761, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23203

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