Because of the asymmetry of six-port junctions and the nonlinearity of diode detectors, the calibration of direction finding receivers have to be carefully considered. It is generally believed that an efficient tool for numerical approximations, the artificial neural network (ANN), may be used for such calibrations. In this paper, a new calibration technique based on the ANN is proposed for direction finding receivers at a bandwidth of 1 GHz. The direction finding system adopts a zero-intermediate frequency receiver architecture, which offers the advantage of fast response times. The key modules of this receiver consist of two six-port networks used to measure phase differences and operating frequencies. The results indicate that the calibration technique achieves a high accuracy of 0.192°.
2. Galwas, B. and S. Palczewski, "Idea of six-port vector-voltmeter with homodyne phase-sensitive detectors," Ninth Instrumentation and Measurement Technology Conference, New York, United States, 1992.
3. Galwas, B. and S. Palczewski, "Broadband homodyne six-port reflectometer," Proc. 21st European Microwave Conference, Stuttgart, Germany, 1991.
4. Zhao, Y., C. Viereck, J. F. Frigon, R. G. Bosisio, and K. Wu, "Direct quadrature phase shift keying modulator using six-port technology," Electronics Letters, Vol. 41, No. 21, 1180-1181, 2005.
5. Boukari, B., E. Moldovan, S. Affes, K. Wu, R. G. Bosisio, and S. O. Tatu, "A heterodyne six-port FMCW radar sensor architecture based on beat signal phase slope techniques," Progress In Electromagnetics Research, Vol. 93, 307-322, 2009.
6. Khaddaj Mallat, N., E. Moldovan, and S. O. Tatu, "Comparative demodulation results for six-port and conventional 60 GHz direct conversion receivers," Progress In Electromagnetics Research, Vol. 84, 437-449, 2008.
7. De la Morena-Alvarez-Palencia, C. and M. Burgos-Garcia, "Four-octave six-port receiver and its calibration for broadband communications and software defined radios," Progress In Electromagnetics Research, Vol. 116, 1-21, 2011.
8. Huyart, B., J.-J. Laurin, R. G. Bosisio, and D. Roscoe, "A direction-finding antenna system using an integrated six-port circuit," IEEE Trans. Antennas Propagation, Vol. 43, No. 12, 1508-1512, 1995.
9. Yakabe , T., F. Xiao, K. Iwamoto, F. M. Ghannouchi, K. Fujii, and H. Yabe, "Six-port based wave-correlator with application to beam direction finding," IEEE Trans. Instrum. Meas., Vol. 50, No. 2, 377-380, 2001.
10. Vinci, G. , A. Koelpin, and R. Weigel, "Employing six-port technology for phase-measurement-based calibration of automotive radar," Microwave Conference, APMC 2009, Singapore, 2009.
11. Hopfield, J. J., "Neural networks and physical systems with emergent collective computational abilities," Proceedings of the National Academy of Sciences of the United States of America, 1982.
12. Liu, Y., "Calibrating an industrial microwave six-port instrument using the artificial neural network technique," IEEE Trans. Instrum. Meas., Vol. 45, No. 2, 651-656, 1996.
13. Cicolani, M. and F. Marchetti, "Phase and amplitude automatic measurements on pulsed RF signals," Twenty-second European Microwave Conference, Helsinki, Finland, Sep. 1992.
14. Pandolfi, C., E. Fitini, G. Gabrielli, E. Megna, and A. Zaccaron, "Comparison of analog IFM and digital frequency measurement receivers for electronic warfare," Seventh European Radar Conference, EuRAD 2010, Paris, France, Sep. 2010.