AbstractIn this article, a cascaded bandstop filter using quarter‐wavelength open‐circuited stub structure is employed to suppress the spurious passband at the second harmonic of the bandpass filter. The center frequency of the fabricated bandpass filter is at 0.9 GHz and the fractional bandwidth is 5%. The proposed bandpass filter shows 30 dB rejection at the second harmonic during the frequency range from 1.1 to 10 GHz. The measured frequency responses of the fabricated filter are in agreement with simulated results. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 863–865, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23226