The UWB filter with using stepped-impedance method and improving out of band rejection

Abstract

In this paper, an ultra-wideband (UWB) bandpass filter is designed by using the stepped impedance method. A stepped impedance structure with low order is proposed, then some of them are used in series. First only one short circuit stub is used then some of them are combined according to frequency response. The result of simulation depicts that the passband is 3.356 to 22.81 GHz, it means bandwidth is over than 19 GHz, therefore the fractional bandwidth is 148.7%, which it is good compared to papers of recent years. Ripple is less than 1dB in band. The insertion loss is over than 25 dB in out of band. The presented filter size is 16×16 mm2 that it is compact. The designed filter is fabricated on RO4003 substrate with 3.38 dielectric constant, 32 mil thickness, and 0.0026 loss tangent. The simulation is performed with numerical software and they confirm each other's results.

Keywords

• uwb filter
• stepped impedance
• out of band rejection
• fractional bandwidth
• series filters