In this paper, a dual-band stub (DBS) comprising one lumped kernel circuit unit cell (KCUC) and two distributed uniform transmission lines is presented. An odd-even mode resonant frequency ratio (OEMRFR) is introduced, which can determine all the element values in the DBS circuit model. Its phase and impedance bandwidth properties are extracted based on the image parameter theory. By adjusting the OEMRFR value, the second working bandwidth and structural size can be controlled simultaneously. On the other hand, the input and output space mapping (IOSM) is exploited to realize a planar microstrip DBS by transferring the lumped KCUC into a quasi-lumped formation. The established ISOM design process is fully automated and can generate the finalized DBS layout with just a few full-wave simulations. A DBS operative at WLAN dual frequencies of 2.4/5.8 GHz with extended bandwidth is designed as an example. Good agreement between the measured and simulated results justifies both the extracted dual-band performance of the proposed DBS and its customized IOSM design process.
2. Chang, L. and T.-G. Ma, "Dual-mode branch-line/rat-race coupler using composite right-/left-handed lines," IEEE Microw. Wireless Comp. Lett., Vol. 27, No. 5, 449-451, 2017.
3. Bonache, J., et al., "Application of composite right/left handed (CRLH) transmission lines based on complementary split ring resonators (CSRRs) to the design of dual-band microwave components," IEEE Microw. Wireless Comp. Lett., Vol. 18, No. 8, 524-526, 2008.
4. Durán-Sindreu, M., et al., "Planar multi-band microwave components based on the generalized composite right/left handed transmission line concept," IEEE Trans. Microw. Theory Tech., Vol. 58, No. 12, 3882-3891, 2010.
5. Selga, J., et al., "Synthesis of split-rings-based artificial transmission lines through a new two-step, fast converging, and robust aggressive space mapping (ASM) algorithm," IEEE Trans. Microw. Theory Tech., Vol. 61, No. 6, 2295-2308, 2013.
6. Caloz, C., "Metamaterial dispersion engineering concepts and applications," Proc. IEEE, Vol. 99, No. 10, 1711-1719, 2011.
7. 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.
8. Wu, G.-C., G. Wang, L.-Z. Hu, Y.-W. Wang, and C. Liu, "A miniaturized triple-band branch-line coupler based on simplified dual-composite right/left-handed transmission line," Progress In Electromagnetics Research C, Vol. 39, 1-10, 2013.
9. Cheng, K.-K. and S. Wong, "A novel dual-band 3-dB branch-line coupler design with controllable bandwidths," IEEE Trans. Microw. Theory Tech., Vol. 60, No. 10, 3055-3061, 2012.
10. Page, J. E. and J. Esteban, "Dual-band matching properties of the C-section all-pass network," IEEE Trans. Microw. Theory Tech., Vol. 61, No. 2, 827-832, 2013.
11. Bai, Y.-F., et al., "Design of compact quad-frequency impedance transformer using two-section coupled line," IEEE Trans. Microw. Theory Tech., Vol. 60, No. 8, 2417-2423, 2012.
12. Li, X., et al., "A quad-band Doherty power amplifier based on T-section coupled lines," IEEE Microw. Wireless Comp. Lett., Vol. 26, No. 6, 437-439, 2016.
13. Arigong, B., J. Shao, M. Zhou, H. Ren, J. Ding, Q. Mu, Y. Li, S. Fu, H. Kim, and H. Zhang, "An improved design of dual-band 3 dB 180° directional coupler," Progress In Electromagnetics Research C, Vol. 56, 153-162, 2015.
14. Koziel, S., J. W. Bandler, and K. Madsen, "A space-mapping framework for engineering optimization - Theory and implementation," IEEE Trans. Microw. Theory Tech., Vol. 54, No. 10, 3721-3730, 2006.
15. Hsu, C.-L., J.-T. Kuo, and C.-W. Chang, "Miniaturized dual-band hybrid couplers with arbitrary power division ratios," IEEE Trans. Microw. Theory Tech., Vol. 57, No. 1, 149-156, 2009.
16. The Mathworks Inc., MATLAB Optimization Toolbox User’s Guide, Version R2016b, Natick, MA, 2015.
17. Pozar, D. M., Microwave Engineering, 4th Ed., Wiley, Hoboken, 2012.
18. Hong, J. S. and M. J. Lancaster, Microstrip Filters for RF/Microwave Applications, Wiley, New York, 2001.
19. The ANSYS Inc., ANSYS Electronics Desktop Online Help, Version 16.0.0, Pittsburgh, PA, 2015.
20. Nosrati, M. and M. Daneshmand, "Substrate integrated waveguide L-shaped iris for realization of transmission zero and evanescent-mode pole," IEEE Trans. Microw. Theory Tech., Vol. 65, No. 7, 2310-2320, 2017.