A novel compact branch-line coupler operating in two arbitrary frequencies is proposed, analyzed and designed. Stepped-impedance stubs are used in the branch-line coupler to achieve dual-band applications. Parameters of the structure are chosen and provided for design guidelines. Broader operating frequency ratios and compactness are achievable. For the purpose of validation, a microstrip coupler operating at 2.4/5.2 GHz is fabricated and measured.
"A Novel Dual-Band Π-Shaped Branch-Line Coupler with Stepped-Impedance Stubs," Progress In Electromagnetics Research Letters,
Vol. 25, 11-20, 2011. doi:10.2528/PIERL11032915
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