Design and Optimization of Tri-Band Open Loop Resonator Filter for BT, WiMAX, WLAN and Wi-Fi Applications

The consumer wireless frequency spectrum is getting denser and overlapping so may signals can cause interference and less data speed. There is need to either switch to new channel or to use newer technologies available. As per FCC new 6GHz band is now open for WLAN & Wi-Fi networks and to filter out other signals a microwave filter could the best mate. This paper proposed a tri-band microstrip filter having rectangular resonator with open loop has been evaluated. Because of its tiny size, lighter weight, cheaper cost, and superior performance, microstrip filters are often chosen over lumped filters at higher frequencies. The construction, refinement, and implementation of a modular tri-band bandpass filter have examined in this research. The proposed low-profile tri-band MS filter with three resonators designed for BT, WiMAX, WLAN and Wi-Fi microwave applications. The physical size of the filter is 30×15 mm2 . The designed filter has full ground and substrate is of FR-4 material having 4.3 dialectic constant and 1.6 mm thickness. The filter is made of four rectangular resonators of diverse dimension. Resonators are arranged in symmetrical geometry. Proposed tri-band bandpass filter is having negative group delay which facilitates the feedforward amplifier circuits. Filters with NGD also helps to reduces the physical size of the microwave circuits. The proposed tri-band filter has passband characteristics on 2.37GHz, 5.36GHz, and 6.15GHz with the insertion loss of 1.03dB, 1.6dB, and 3.67dB having return loss of 23.3dB, 18.56dB, 12.8dB, and 21.87dB. Filter exhibits good fractional bandwidth of 21.92%, 6.68%, and 4.36% respectively. Proposed filter has 2 transmission zeros. The tested and simulated results of |S11| and |S21| parameters are quite identical which shows the excellent matching of physical parameters. Keywords - Tri-band, band-pass filter, NGD, rectangular resonators, BT, WiMAX, WLAN, Wi-Fi.