A Low-Cost Compact Planar Dual-Band 3 dB Branch Line Coupler Using an Unbalanced CRLH
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In this work, a compact dual-band 3 dB branch line coupler (BLC) is designed with center frequency at 2.45 GHz and 5.08 GHz using an unbalanced composite right/left-handed transmission line. Based on the two-port ABCD parameters, the lumped equivalent circuit of the proposed TL is extracted and optimized to obtain characteristic impedance at 2.45 GHz and 5.08 GHz. The right- and left-handed characteristics of the proposed TL are examined. Incorporating the proposed TL, a dual-band BLC with 0.29λg × 0.3λg size is obtained. The frequency response has magnitude imbalance of 0.8 dB, phase imbalance of 1.8° and 160 MHz bandwidth at 2.45 GHz and magnitude imbalance of 0.81 dB, phase imbalance of 0.006° and 100 MHz bandwidth at 5.08 GHz.
KeywordsInterdigital capacitor CRLH TL Unbalanced CRLH TL Open stub Dual band Branch line coupler (BLC)
The authors want to acknowledge Mr. Avinash Chandra (Senior Research Fellow, ISM Dhanbad) for extending his help in the completion of the project.
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