A dual mode filter with wideband suppression

Abstract

This paper presents a novel method to suppress the harmonic responses of dual mode bandpass filters. The harmonic suppression is based on discriminating coupling. The coupling coefficient at fundamental resonant frequency can be tuned to desirable value whereas it is approaching to zero at high-order harmonic. The coupling region blocks the high-order harmonic but still allows the transmission of signals at passband frequency. Benefiting from this feature, the high order harmonic can be suppressed without degrading the passband performance. Furthermore, no additional circuit is needed. An example filter is implemented, and experimental results are presented to verify the proposed method.

Acknowledgment

This work was supported in part by the National Basic Research Program of China under Grant 2009CB320204 and in part by the National Natural Science Foundation of China under Grants 60821062 and 61001014.