Ultra Wideband Bandpass Filter with Sharp Selectivity Using Interdigitated Structure

In this paper, an ultra-wideband (UWB) bandpass filter (BPF) is proposed, which is formed by an interdigitated structure and a defected ground structures (DGS) and four short-circuited branches. This filter has sharp selectivity due to two zeros at low frequencies. One of the two low-frequency zeros of the filter is at 1.2 GHz and the other is at 3.8 GHz. The proposed filter has a working frequency range of 3.85 GHz to 11.83 GHz and the center frequency is 7.89 GHz. The filter was designed using a RT/Duroid 5870 medium with a thickness of 0.862 mm. The total fractional bandwidth is 101%.