Design and implement of compact UWB bandpass filter with a frequency notch by consisting of coupled Microstrip line structure, DGS and EOS

In this paper, an ultra-wideband (UWB) bandpass filter with a frequency notch is designed and implemented. The proposed filter is based on coupled microstrip line with U-shaped defected ground structure (DGS). By introducing embedded open stubs (EOS) into input and output feed lines, the UWB bandpass filter can get a band-notched characteristic at the appointed frequency band. Several compensatory lines are introduced to compensate the damage bringing by EOS. The test results show that 3 dB pass-band is from 3.1 GHz to 10.6 GHz. The depth of the frequency notch is about -30 dB at 5.8 GHz, which is deep enough to choke back interference from other wireless communication systems operating at the same frequency. The insertion loss in the pass-band is less than 1 dB (including the insertion loss of two SMA connectors).