Arbitrary Dual-Band Components Using Composite Right/Left-Handed Transmission Lines

TLDR

The paper presents arbitrary dual‑band microstrip components based on composite right/left‑handed transmission lines, detailing their theory, synthesis, and implementation. Dual‑band operation is achieved by tuning the frequency offset and phase slope of the CRLH TL, allowing noninteger frequency ratios, and the design is applied to λ/4 open/short stubs, a branch‑line coupler, and a rat‑race coupler. Simulations and measurements confirm the dual‑band components meet the specified performance, with the short‑circuit stub loss < 0.25 dB, open‑stub loss > 23 dB, BLC S21/S31 > –4 dB, return loss > 17 dB, isolation > 13 dB, phase ±1.5°, gain imbalance < 0.5 dB, and RRC S21/S31 > –4 dB, return loss > 12 dB, isolation > 30 dB, phase 180° ± 4°, and gain imbalance < 0.2 dB.

Abstract

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 (/spl lambda//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 /spl lambda//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 /spl lambda//4 CRLH TL open-circuit stub and less than 0.25 dB for the shunt /spl lambda//4 CRLH TL short-circuit stub at each passband. The dual-band BLC exhibits S/sub 21/ and S/sub 31/ larger than -4.034 dB, return losses larger than 17 dB, isolations larger than 13 dB, phase differences 90/spl deg//spl plusmn/1.5/spl deg/, and gain imbalance less than 0.5 dB at each passband. The dual-band RRC exhibits S/sub 21/ and S/sub 31/ larger than -4.126 dB, return losses larger than 12 dB, isolations larger than 30 dB, phase difference 180/spl deg//spl plusmn/4/spl deg/, and gain imbalance less than 0.2 dB at each passband.