Dual-band microstrip notch filters using slotted square patch resonators

In this paper a novel dual-band microstrip notch filter is introduced using slotted square patch resonators. The gaps made on the patch load to the reduction of patch size and enhancement of the filter quality factor. Two resonance modes are excited in each filter frequency bandwidth, which cause the quality factor to increase and the value of S₂₁ decrease at the center frequency of the filter reject band. The gaps cut on the patch make the resonance modes in each band approach each other. Furthermore, the variation of the lengths of slots, displace the reject bands of filters. In this paper, the reject bands of the filter are designed for the WLAN bands, namely 2.4 GHz and 5.2 GHz. Consequently, one of the applications of such notch filters may be to reject the WLAN frequency bands from the UWB communication systems. One prototype model is fabricated and tested. The computer simulation results and measurement data agree very well in the specified frequency band.