Design and fabrication of a dual-band band-pass filter using dual-mode square patch resonator and ring-shaped slot

In this paper, a band-pass filter with suitable performance for wireless telecommunication applications is designed and fabricated. For designing the proposed filter, the dimensions of dual-mode square patch resonator are chosen to be within a quarter of the wavelength. Circular perturbations (circular slots) are used for better performance of the proposed filter. A dual channel filter is designed and fabricated on an FR4 substrate. The center frequency of the proposed filter for the first channel is equal to 2.35 GHz and for the second channel is equal to 3.375 GHz; the 3-dB fractional bandwidths (FBWs) of 12.75 and 10.3 %, respectively. The measured insertion losses are 0.8 and 1.45 dB, respectively. The proposed filter has a small size of 20 mm×  20mm. The group delay of the proposed filter for the first and second pass bands is almost constant, which indicates phase of the insertion loss in the pass bands is linear. The proposed filter is fabricated and tested. The results of simulation are fairly consistent with that of the measurement. The proposed filter can be used in wireless communications and modern microwave telecommunication.