A dual-band 180° hybrid coupler with a filter response

This study presents a dual-band 180° hybrid coupler with a filter response. The hybrid coupler consisting of four coupled stepped-impedance resonators has a second-order Chebyshev filter response. A 2.45/5.8-GHz filtering 180° hybrid coupler has been designed and fabricated on a Rogers RO4003C substrate for WLAN applications. The insertion loss 1/|S
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| is about 3+1.2/3+1.5 dB, and isolation are better than 24 dB. The proposed design can be used for dual-band and multifunctional applications.