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8 - Design, modeling, and linearization of mixers, modulators, and demodulators

Published online by Cambridge University Press:  05 July 2011

Patrick Roblin
Patrick Roblin
Affiliation:
Ohio State University
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Summary

This chapter is concerned with the system design, behavioral modeling, experimental characterization, balancing, and linearization of I–Q modulators and mixers. The K-parameters are first introduced for the purpose of linear modeling and balancing. The extraction of the K-matrix from LSNA measurements and a modulator–demodulator chain is discussed. The polyphase up-converter topology which permits the realization of linear single-sideband mixers is introduced next. The nonlinear modeling of the single-sideband mixer is then discussed. Finally the linearization of single-sideband mixers using the poly-harmonic predistortion technique is presented. These techniques offer some interesting options for the filterless implementation of wideband software-defined radio (SDR).

Vector characterization of an I–Q modulator

Balancing of an I–Q modulator

The balancing of I–Q modulators and demodulators is of critical importance in wireless systems, especially for modern multi-carrier techniques (OFDM) employing higher-order modulations such as QAM-64. This problem has been approached from the receiver side using adaptive equalization techniques using known preambles [1] [2]. Balancing is also of importance in multi-band predistortion linearization of the transmitter power amplifiers. As we shall see in Chapter 9 when introducing a frequency-selective predistortion linearization algorithm that differentially linearizes the signal in different bands [3], a balanced modulator is required in order for this linearization scheme to be effective.

An effective technique has been developed for balancing modulators [4]. This approach relies on the initial K-matrix modeling of I–Q modulators [5].

Type
Chapter
Information
Nonlinear RF Circuits and Nonlinear Vector Network Analyzers
Interactive Measurement and Design Techniques
 , pp. 237 - 261
Publisher: Cambridge University Press
Print publication year: 2011

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References

[1] Jian, Lin and E., Tsui, “Joint adaptive transmitter/receiver IQ imbalance correction for OFDM systems,” in IEEE International Symposium on PIMRC, Vol. 2, pp. 1511–1516, 2004.Google Scholar
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[3] P., Roblin, Sukkeun, Myoung, D., Chaillot, Young Gi, Kim, A., Fathimulla, J., Strahler, and S., Bibyk, “Frequency selective predistortion linearization of RF power amplifiers,” IEEE Transactions on Microwave Theory and Techniques, Vol. 56, No. 1, pp. 65–76, Jan. 2008.Google Scholar
[4] Behzad, Razavi, RF Microelectronics, Prentice Hall, 1998.Google Scholar
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[7] S. K., Myoung, X., Cui, P., Roblin, D., Chaillot, F., Verbeyst, M., Vanden Bossche, S. J., Doo, and W., Dai, “Large signal network analyzer with trigger for baseband modulation linearization,” in 64th ARFTG Conference Digest, Orlando, FL, 2004.Google Scholar
[8] S., Mutha, P., Roblin, D., Chaillot, X., Yang, K., Jiwoo, J., Strahler, R., Rojas-Tehra, and J., Volakis, “Technique for joint balancing of IQ modulator–demodulator chains in wireless transmitters,” in 2009 Microwave Symposium Digest, pp. 221–224, 2009.Google Scholar
[9] E., Mensink, E. A. M., Klumperink, and B., Nauta, “Distortion cancellation by polyphase multipath circuits,” IEEE Transactions on Circuits and Systems I, Vol. 52, No. 9, pp. 1785–1794, Sept. 2005.Google Scholar
[10] R., Shrestha, E. A. M., Klumperink, E., Mensink, G. J. M., Wienk, and B., Nauta, “A polyphase multipath technique for software-defined radio transmitters,” IEEE Journal of Solid-State Circuits, Vol. 41, No. 12, pp. 2681–2692, Dec. 2006.Google Scholar
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[12] X., Yang, D., Chaillot, P., Roblin, W.-R., Liou, J., Lee, H. D., Park, J., Strahler, and M., Ismail, “Poly-harmonic modeling and predistortion linearization for software defined radio upconverters,” IEEE Transactions on Microwave Theory and Techniques, Vol. 58, No. 8, pp. 2125–2133, Aug. 2010.Google Scholar

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