In this paper, a novel four-port symmetric coupled composite right-/left-handed (CRLH) transmission line in common-/differential-mode operation is introduced. The symmetric metamaterial structure is based on a unit-cell which under a differential-mode excitation behaves like a CRLH metamaterial with bandpass filter characteristics. In contrast, the CRLH metamaterial is below the cut-off frequency under a common-mode excitation. To validate these features, a five-cell four-port symmetric CRLH-TL is simulated, fabricated, and measured, and the obtained results verify the bandpass filter features of the structure under differential-mode excitation.
2. Chen, C.-C., Y.-R. Chen, and C.-Y. Chang, "Miniaturized microstrip coupled-line bandpass filters using quarter-wave or quasi-quarter-wave resonators," IEEE Trans. Microwave Theory & Tech., Vol. 51, No. 1, 120-131, Jan. 2003..
3. Bockelman, D. E. and W. R. Eisenstant, "Combined differential and common-mode scattering parameters: Theory and simulation," IEEE Trans. Microwave Theory & Tech., Vol. 43, No. 7, 1530-1539, Jul. 1995.
4. Goto, R., H. Deguchi, and M. Tsuji, "Composite right/left-handed transmission lines based on conductor-backed coplanar strips for antenna application," Proceeding of the 36th European Microwave Conference, 1040-1043, Sep. 2006.
5. Liu, C. and W. Menzel, "Broadband via-free microstrip balun using metamaterial transmission lines," IEEE Microwave Wireless Compon. Lett., Vol. 18, No. 7, 437-439, Jul. 2008.
6. Kim, Y., E. Kim, A. Lai, D. S. Goshi, and T. Itoh, "Integrated mixer based on composite right/left-handed leaky-wave antenna," 2008 IEEE MTT-S Int. Microwave Symp., 1317-1320, Jun. 2008.
7. Le, L., C. Caloz, and T. Itoh, "Dominant mode leaky-wave antenna with backfire-to-endfire scanning capability," Electron. Lett., Vol. 38, No. 23, 1414-1416, Nov. 2002.
8. Hashemi, M. R. and T. Itoh, "Dispersion engineered metamaterial-based transmission line for conformal surface application," 2008 IEEE MTT-S Int. Microwave Symp., 331-334, Jun. 2008.
9. Cao, W.-Q., B. Zhang, A. Liu, T. Yu, D. Guo, and Y. Wei, "Novel phase-shifting characteristic of CRLH-TL and its application in the design of dual-band dual-mode dual polarization antenna," Progress In Electromagnetics Research, Vol. 131, 375-390, 2012.
10. Caloz, C. and T. Itoh, Electromagnetic Metamaterials Transmission Line Theory and Microwave Application, J. Wiley & Sons, New Jersey, 2006.
11. Casares-Miranda, F., P. Otero, E. Marquez-Segura, and C. Camacho-Pealosa, "Wire bonded interdigital capacitor," IEEE Microwave Wireless Compon. Lett., Vol. 15, No. 10, 700-702, Oct. 2005.