A compact low-pass filter (LPF) with ultrabroad stopband characteristic is presented in this article. This filter mainly consists of a rectangular stub resonator and cumulative open-circuited stubs, providing multiple transmission zeros to form a wide stopband region. Further, two open stub loads are simply adopted to improve the band selectivity. This fabricated LPF exhibits a 3 dB cutoff frequency (fc) at 1.74 GHz with an average low insertion loss of 0.25 dB and a broad stopband region from 2.6 to 22.8 GHz (10.8c) under a high rejection level of 20 dB.
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