New Compact Dual-Band Bandpass Filter Using Stepped Impedance Resonator and U-Shaped Microstrip Structure

Abstract

This paper presented a design to realize a compact dual-band bandpass filter using a pair of coupled symmetric stepped impedance resonator (SIRs) and U-shaped microstrip structure for wireless communication applications. To obtain its compact size, the symmetric SIR was bent like an L-shape. The U-shaped microstrip structure was designed and integrated into the SIR to achieve notch bandstop response so as to produce the specified dual-band bandpass filter. For the resonant frequency and attenuation, the U-shaped microstrip structure was designed at 3GHz and greater than 60dB respectively. Based on the simulation and experimental results, it was verified that this proposed design produced two passbands centered at 2.5GHz and 3.5GHz with the fractional bandwidth of more than 16%. The return loss and insertion loss are better than 15dB and 1dB respectively. The simulated and measured results are both presented and showed a good agreement. This proposed dualband bandpass filter is beneficial in modern wireless communication and many other applications such as WiMAX and WLAN.