Arbitrary dual-band components using composite right/left-handed transmission lines

Arbitrary dual-band microstrip components using composite right/left-handed (CRLH) transmission lines (TLs) are presented. Theory, synthesis procedure, and implementation of the dual-band quarter-wave (λ/4) CRLH TL are presented. Arbitrary dual-band operation is achieved by the frequency offset and the phase slope of the CRLH TL. The frequency ratio of the two operating frequencies can be a noninteger. The dual-band λ/4 open/short-circuit stub, dual-band branch-line coupler (BLC), and dual-band rat-race coupler (RRC) are also demonstrated. The performances of these dual-band components are demonstrated by both simulated and measured results. Insertion loss is larger than 23 dB for the shunt λ/4 CRLH TL open-circuit stub and less than 0.25 dB for the shunt λ/4 CRLH TL short-circuit stub at each passband. The dual-band BLC exhibits S₂₁ and S₃₁ larger than -4.034 dB, return losses larger than 17 dB, isolations larger than 13 dB, phase differences 90°±1.5°, and gain imbalance less than 0.5 dB at each passband. The dual-band RRC exhibits S₂₁ and S₃₁ larger than -4.126 dB, return losses larger than 12 dB, isolations larger than 30 dB, phase difference 180°±4°, and gain imbalance less than 0.2 dB at each passband.