volume | PIER Journals

2008-10-27

Applying Critical-Points Method in the Presence of Phase Shift Due to Feed Line

Changying Wu,

Dr. Changying Wu

Northwestern Polytechnical University

China

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Kai Zhang,

Dr. Kai Zhang

School of Electronics and Information

Northwestern Polytechnical University

China

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Gao Wei,

Dr. Gao Wei

School of Electronic and Information

Northwestern Polytechnical University

China

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Jia-Dong Xu

Professor Jia-Dong Xu

School of Electronic and Information

Northwestern Polytechnical University

China

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Progress In Electromagnetics Research M, Vol. 5, 15-23, 2008

doi:10.2528/PIERM08100704

Abstract

The critical-points method is adopted for measuring unloaded Q-factor of microwave resonators in the presence of phase shift caused by the feed line. The result is calculated from four frequencies of three points in the resonator's impedance trace. In fact, the resonator's impedance trace rotates in Smith Chart by the phase shift. If Q-factor were gotten directly from the measured impedance including feed line rather than the equivalent impedance of the resonator without feed line, the performance of measurement will be impaired. To de-embed the phase shift, objective function was introduced to find the proper rotation angle caused by the feed line instead of calibration using extra measurement. Another advantage of the proposed method lies in the fact that no special attention is needed to distinguish magnetic coupling and electric coupling. The effectiveness of the proposed method was demonstrated by one set of simulation data and two measurement examples, namely, a low Q dielectric resonator and a high Q hollow cylindrical cavity.

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Changying Wu, Kai Zhang, Gao Wei, and Jia-Dong Xu, "Applying Critical-Points Method in the Presence of Phase Shift Due to Feed Line," Progress In Electromagnetics Research M, Vol. 5, 15-23, 2008.
doi:10.2528/PIERM08100704

References

1. Kumar, A., S. Sharma, and G. Singh, "Measurement of dielectric constant and loss factor of the dielectric material at microwave frequencies," Progress In Electromagnetics Research, Vol. 69, 47-54, 2007.
doi:10.2528/PIER06111204

2. Kajfez, D., S. Chebolu, M. R. Abdul-Gaffoor, and A. A. Kishk, "Uncertainty analysis of the transmission-type measurement of Q-factor," IEEE Trans. Microw. Theory Tech., Vol. 47, No. 3, 367-371, 1999.
doi:10.1109/22.750244

3. Kajfez, D., "Q-factor measurement with a scalar network analyzer," Proc. Inst. Elect. Eng., Vol. 142, No. 5, 369-372, Pt. H, 1995.

4. Kajfez, D. and E. J. Hwan, "Q-factor measurement with network analyzer," IEEE Trans. Microw. Theory Tech., Vol. 32, No. 7, 666-670, 1984.
doi:10.1109/TMTT.1984.1132751

5. Sun, E. Y. and S. H. Chao, "Unloaded Q measurement --- The critical points method," IEEE Trans. Microw. Theory Tech., Vol. 43, No. 8, 1983-1986, 1995.
doi:10.1109/22.402290

6. Wang, P., L. H. Chua, and D. Mirshekar-Syahkal, "Accurate characterization of low-Q microwave resonator using criticalpoints method," IEEE Trans. Microw. Theory Tech., Vol. 53, No. 1, 349-353, 2005.
doi:10.1109/TMTT.2004.839931

7. Chua, L. H. and D. Mirshekar-Syahkal, "Accurate and direct characterization of high-Q microwave resonators using one-port measurement," IEEE Trans. Microw. Theory Tech., Vol. 51, No. 3, 978-985, 2003.
doi:10.1109/TMTT.2003.808711