AbstractA compact nonresonating, dual‐band bandstop filter is proposed. By connecting two transmission lines with proper characteristic impedances and phase delay (one is 90° and the other one is 450° in electrical length at center frequency), a dual stopband with two transmission zeros at each stopband is obtained. A prototype is demonstrated for 2.4/5.8‐GHz applications. The measured results show the dual fractional stopband bandwidths with 20‐dB signal attenuation are 25.2% and 12.4%. Also, the theoretical simulation, electromagnetic simulation, and the measured results show good agreement with this simple design. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2952–2954, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24753