A new tri-band bandpass filter for Gsm, wimax and ultra-wideband responses by using asymmetric stepped impedance resonators

In this paper, a design of new tri-band bandpass filter for the application of GSM (1.8 GHz), WiMAX (2.7 GHz) and UWB (3.3- 4.8 GHz) is proposed. The first two narrow passbands are created, and the bandwidth of the third passband can be tuned by properly selecting the impedance ratio (R) and physical length ratio (u) of the asymmetric stepped-impedance resonator. To improve passband performance and form the UWB passband, a U-shape defected ground structure and extra extended coupling lines are integrated with the asymmetric SIR. Due to the three transmission zeros appearing near the passband edges, the band selectivity of the proposed filter is much improved. The filter was fabricated, and the measured results have a good agreement with the full-wave simulated ones.