Design of a compact ultra-wideband bandpass filter with two notched bands

In this paper, a compact ultra-wideband (UWB) band-pass filter (BPF) with two steep rejected notch-bands is proposed. The designed UWB BPF is realized by cascading two interdigital hairpin resonator units with asymmetric open loading stubs and a spiral slot on microstrip line. The asymmetric loading stubs and spiral slot are studied and adopted to introduce notched bands. The lengths and the widths of the stubs and slots can control the notched band in a desired frequency. Finally, simulated results are presented, which are in good agreement with the measured results.