A novel compact wideband b andpass filter using rotational symmetric loaded structure is proposed in this paper. A λ/4 parallel coupled line is first introduced to form a passband with desired center frequency. The rotational symmetric structure with short/open circuit stubs is then introduced as a loading structure to improve the filter's performance. The rotational symmetric loading structure is discussed in detail in this paper, and a pair of transmission zeros is obtained and located at two sides of the passband to improve the passband selectivity intensively. Moreover, three open circuit stubs are utilized to replace one single stub for obtaining a wide stopband. At last, the proposed filter is fabricated and measured, and the results show a good agreement with each other.
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