Performance of periodic grooves on harmonic rejection in C band folded edge coupled microstrip band pass filters

摘要

Design of a miniaturized and compact V-shaped half-wavelength edge-coupled microstrip bandpass filter with improved harmonic suppression is presented. The proposed filter is designed at a center frequency of 5.25 GHz with 20% fractional bandwidth (4.75-5.80 GHz) applicable in WLAN. The conventional parallel-coupled bandpass filter structure has been folded symmetrically about horizontal plane and consecutive square and rectangular shaped periodic grooves are inserted to the parallel lines. Thus, the 2nd harmonic is suppressed significantly to -44.38 dB and 43.71 dB and a size reduction of 59.05% and 59.67% is achieved for square and rectangular grooves respectively with respect to the conventional filter.