A novel G-shaped slot ultra-wideband (UWB) bandpass filter with a very narrow notched band is proposed. The basic ultra-wideband filter is short-circuited stub bandpass filter consisting of shunted λ/4 short-circuited stubs and λ/4 connecting lines. To avoid the interferences such as WLAN signals. The G-shaped slot embedded in the stub filter is used to obtain the notched band inside the UWB passband. Additional U-shaped defected ground structures are adopted to improve the out-band suppression. Measured results show that the proposed filter has an ultra-wide bandwidth from 3.1 GHz to 10.6 GHz, and the insertion loss is less than 1 dB. Specifically, the fabricated filter possesses a 10 dB notched fractional bandwidth (FBW) of 2.36% at the notched center frequency of 5.8 GHz. It also achieves a stop band with 20 dB attenuation.
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