Ultra-wideband bandpass filter with notch and upper-band suppression

A novel ultra-wide band (UWB) bandpass filter (BPF) rejecting two unnecessary bands is proposed. The filter consists of a modified stepped impedance resonator (SIR) and four interdigital coupled lines in the main part. Three pairs of open stubs are connected to the SIR in order to make notch in the passband and reject the upper-stopband. By optimizing the length, width and location of the stubs, -10dB suppression is realized from 5.15 GHz to 5.8 GHz and from 11 GHz to 30 GHz. The proposed filter size is 16.4 × 4.2 mm². 2.5 dimentional EM simulator was used to optimize the filter layout, and the measured results are good agreement with the simulated responses. The 3 dB bandwidth of our proposed UWB BPF is from 3.2 to 4.9 GHz and form 6.2 to 10.5 GHz in experiment.