Dual-band bandpass filter for WLAN application using coupled three-line microstrip structure

A novel wide stop band with high attenuation in stop band dual-band micro strip band pass filter for wireless local area network products (WLAN) are designed using the concept of coupled line micro strip structure. Wireless local area network products (WLAN) operate at 2.4GHz to 2.5GHz and 5.235 GHz to 5.350 GHz bands. Finally, a new dual-band filter is designed, and it is demonstrated that good impedance matching at all the two ports and excellent selectivity between two pass bands which extends from 2.33 GHz to 2.63GHz and 4.5GHz to 5.37GHz are obtained. The simulated return loss is greater than 12 dB over the pass bands. The group delay is less than 2.4 ns over across the first pass band and it is less than 1.5ns over across the other pass band In addition, the existence of three transmission zeros one in between two pass band and other two on both sides of the pass band improves the selectivity of the proposed filter. The insertion loss at the center frequencies 2.5GHz and 4.87GHz are 2.14 dB and 2.77 dB respectively.