Design of a Hairpin SIR Dual-Band Bandpass Filter with Defected Ground Slots for WLAN Application

An efficient and practical method in designing a dual-band bandpass filter operating at 2.4 and 5.2 GHz for WLAN application is presented. The proposed filter is designed by utilizing stepped impedance resonator (SIR) in hairpin-line configuration to make the structure compact and defected ground slots is introduced to attain a high coupling coefficient to enhance the performance of frequency response. The proposed design of the dual-band bandpass filter is simulated in CST Studio Suite software and fabricated using RO4003C substrate with relative permittivity of 3.55, thickness of 1.524 mm and loss tangent of 0.002. The simulation result shows low insertion loss with 1.42 dB and 1.11 dB, high return loss with 35.74 dB and 32.67 dB, fractional bandwidth (FBW) of 263 MHz (10.9%) and 349.4 MHz (6.5%) respectively at 2.4 and 5.2 GHz. The simulated and experimental results are well correlated. The proposed filter has been compared with other designs in this paper and demonstrated higher return loss compared to others.