AbstractA new mixed‐coupled quint‐wideband ASIR bandpass filter with low insertion loss and compact size is proposed: spiral and open‐loop coupled structures realize fundamental mode coupling and enhance another four spurious modes with optimum insertion loss. The fundamental frequency and four spurious frequencies are located at 1.275 GHz with fractional bandwidth (FBW) of 38.4%, 3.225 GHz with FBW of 38.4%, 5.875 GHz with FBW of 12.1%, 7.515 GHz with FBW of 13.7%, 9.74 GHz with FBW of 4.3%. The filter is suitable for multiple applications including GPS, Wi‐Fi and IEEE 802.11a, and partially for IEEE 802.16. The quint‐wideband filter has a performance superior to its currently proposed quint‐wideband counterparts.