A polygonal open-loop resonator compact bandpass filter for Bluetooth and WLAN applications

Abstract

In this paper, a new bandpass filter is designed using two open-loop resonators with polygonal forms. The use of polygonal forms leads to compact size and broad bandwidth behavior. The overall filter dimensions are 8×16 mm2, which correspond to 0.4λg × 0.2λg using a substrate with Rogers Ro 3010 with a relative permittivity of 10.2 and a thickness of 1.5 mm. The resulting filter exhibits enhanced passband behavior with two transmission zeros. The resulting passband has a centre frequency of 2.40 GHz, and a bandwidth of 230 MHz and fractional bandwidth (FBW) of 10%, with return loss of about −26 dB and insertion loss equal to −0.8 dB. The locations of the two transmission zeros are at 2.176 GHz and 2.638 GHz, which means that there is a sharp cut before and beyond the passband. The simulation and performance evaluation of the proposed filter were carried out using Microwave Studio Suite (MWS) Computer Simulation Technology (CST). The resulting performance of the proposed filter makes it very desirable for Bluetooth and WLAN applications (IEEE 802.11n).