Harmonic-rejected compact bandpass filter using dual-mode microstrip resonator with additional open stub.

In this article, a compact dual-mode λ_g/2 bandpass filter with the characteristic of harmonic rejection is designed and implemented.The second and third harmonics of the suggested bandpass filter are rejected by using the additional open stubs of the T-type equivalent circuit for the quarter wavelength line. Also, the J-inverter is investigated as functions of the impedance and electrical length of the open stub of dual-mode λ_g/2 resonator. From the results, the lower impedance of open stub of dual-mode λ_g/2 resonator is better for the good performance of the dual-mode λ_g/2 bandpass filter. The harmonic-rejected dual-mode λ_g/2 bandpass filter shows the characteristic of suppression of harmonics until 8 GHz and the insertion and return losses of 0.96 and 18.89 dB, respectively, at the center frequency of 2.43 GHz. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2288–2291, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25457 [ABSTRACT FROM AUTHOR]