In this paper, a new approach to build a dual-band impedance transformer is presented. The transformer can handle impedances that are complex and vary with frequency. This transformer contains a Pi-section structure, which can be equivalent to having two different electrical lengths at the two operating frequencies. One of the electrical lengths serves as complementary angle of the other. In this way, the conjugate impedances obtained through previous process are transformed to real impedance concurrently. All parameters are derived from closed-form equations. In addition, several simulations as well as a fabricated power amplifier (PA) are presented to verify the proposed transformer. The measured result performs a good agreement with the simulated one in return loss and gain. This transformer may find use in different stages of a transceiver such as power amplifiers which operate at two independent frequencies.
2. Kuo, J.-T., C.-Y. Fan, and S.-C. Tang, "Dual-wideband bandpass filters with extended stopband based on coupled-line and coupled three-line resonators," Progress In Electromagnetics Research, Vol. 124, 1-15, 2012.
3. Jiménez-Martín, J. L., V. González-Posadas, J. E. González-García, F. J. Arques-Orobon, L. E. Garcia-Munoz, and D. Segovia-Vargas, "Dual band high efficiency class CE power amplifier based on CRLH diplexer," Progress In Electromagnetics Research, Vol. 97, 217-240, 2009.
4. Wei, K. P., Z. Zhang, and Z. Feng, "Design of a dual-band omnidirectional planar microstrip antenna array," Progress In lectromagnetics Research, Vol. 126, 101-120, 2012.
5. Cheng, K.-K. M. and F.-L. Wong, "A novel approach to the design and implementation of dual-band compact planar 90° branch line coupler," IEEE Transactions on Microwave Theory and Techniques, Vol. 52, No. 11, 2458-2463, 2004.
6. Chen, X.-Q., X.-W. Shi, Y.-C. Guo, and M.-X. Xiao, "A novel dual band transmitter using microstrip defected ground structure," Progress In Electromagnetics Research, Vol. 83, 1-11, 2008.
7. Rawat, K., M. S. Hashmi, and F. M. Ghannouchi, "Dual-band RF circuits and components for multi-standard software defined radios ," IEEE Circuits and Systems Magazine, Vol. 12, No. 1, 12-32, 2012.
8. Chow, Y. L. and K. L. Wan, "A transformer of one-third wavelength in two sections - For a frequency and its first harmonic ," IEEE Microwave and Wireless Components Letters, Vol. 12, No. 1, 22-23, 2002.
9. Monon, C., "A small dual frequency transformer in two sections," IEEE Transactions on Microwave Theory and Techniques, Vol. 51, No. 4, 1157-1161, 2003.
10. Orfanidis, S. J., "A two-section dual-band Chebyshev impedance transformer," IEEE Microwave and Wireless Components Letters, Vol. 13, No. 9, 382-384, 2003.
11. Castaldi, G., V. Fiumara, and I. Gallina, "An exact synthesis method for dual-band Chebyshev impedance transformers," Progress In Electromagnetics Research, Vol. 86, 305-319, 2008.
12. Wu, Y., Y. Liu, and S. Li, "A compact Pi-structure dual band transformer," Progress In Electromagnetics Research, Vol. 88, 121-134, 2008.
13. Colantonio, P., F. Giannini, and L. Scucchia, "A new approach to design matching networks with distributed elements," 15th International Conference on Microwaves, Radar and Wireless Communications, MIKON-2004, Vol. 3, 811-814, 2004.
14. Ji, S. H., C. S. Cho, J. W. Lee, and J. Kim, "Concurrent dual-band class-E power amplifier using composite right/left-handed transmission lines ," IEEE Transactions on Microwave Theory and Techniques, Vol. 55, No. 6, 1341-1347, 2007.
15. Liu, X., Y. A. Liu, S. L. Li, F. Wu, and Y. L. Wu, "A three-section dual band transformer for frequency-dependent complex load impedance," IEEE Microwave and Wireless Components Letters , Vol. 19, No. 10, 611-613, 2009.
16. Nikravan, M. A. and Z. Atlasbaf, "T-section dual-band impedance transformer for frequency-dependent complex loads," Electronics Letters, Vol. 47, No. 9, 551-553, 2011.
17. Rawat, K. and F. M. Ghannouchi, "Dual-band matching technique based on dual-characeristic impedance transformers for dual-band power amplifier design ," IET Microwaves, Antennas & Propagation, Vol. 5, No. 14, 1720-1729, 2011.
18. Chuang, M.-L., "Dual-band impedance transformer using two-section shunt stubs," IEEE Transactions on Microwave Theory and Techniques, Vol. 58, No. 5, 1257-1263, 2010.
19. Wu, Y. L., Y. A. Liu, and S. L. Li, "A dual-frequency transformer for complex impedances with two unequal sections," IEEE Microwave and Wireless Components Letters, Vol. 19, No. 2, 77-79, 2009.
20. Liu, Y., Y.-J. Zhao, and Y. Zhou, "Lumped dual-frequency mpedance transformers for frequency-dependent complex loads," Progress In Electromagnetics Research, Vol. 126, 121-138, 2012.
21. Fagotti, R., A. Cidronali, and G. Manes, "Concurrent hex-band GaN power amplifier for wireless communication systems," IEEE Microwave and Wireless Components Letters, Vol. 21, No. 2, 89-91, 2011.