Parallel-coupled microstrip filters with over-coupled end stages for suppression of spurious responses |
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Authors: | Jen-Tsai Kuo Sin-Ping Chen Meshon Jiang |
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Affiliation: | Dept. of Commun. Eng., Nat. Chiao Tung Univ., Hsinchu, Taiwan; |
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Abstract: | In a parallel-coupled microstrip filter, end stages with over-coupling are designed to suppress the unwanted responses at twice the passband frequency (2f/sub 0/). The inherent transmission zero of an over-coupled input/output stage is shown tunable. It is found that increasing the image impedance of the filter sections can further enhance the suppression. The designed bandpass filters thus have a wide upper stopband and improved passband response symmetry. Measured results of fabricated circuits show that the idea works very well. |
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