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Abstract
Two novel ultra-wideband (UWB) bandpass filters (BPFs) with multiple notched bands are presented. A stub-loaded multiple-mode resonator is used to realize an ultra-wide bandwidth, and two L-shape folded shunt open-circuited stubs are placed on the feed lines to control the quantity and frequency of notched bands within the desired bandwidth. This improves the selectivity and rejection of the filters as well. Then the stepped impedance structure connected with the feed lines on both sides is introduced to enhance the return loss performance. Finally, the prototypes of the UWB BPFs with triple and quad notched bands are implemented and measured. A good agreement between the predicted and measured results is obtained.
Acknowledgment
This work is supported by the Fundamental Research Funds for the Central Universities (ZYGX2009J041 and ZYGX2010J043), the National Natural Science Foundation of China (60901023), and the DPR Foundation (9140A03011210DZ02).