In this paper antenna measurements in the presence of multipath waves are discussed. Methods are proposed to diagnose the degradation sources of a compact range measurement system operating at a frequency much lower than the designed frequency range. A range-gating technique is employed to improve the capability of the compact range measurement system. With this technique, the field responses over a bandwidth for each rotation angle are coherently measured, and the fast Fourier transform is applied to obtain the range profile. A suitable window function is applied to extract the desired path and eliminate all other undesired paths. The antenna pattern is plotted according to the filtered response of the desired path. We have expressed the receiving voltage of a testing antenna in terms of its gain pattern and input impedance of the testing antenna operating in multipath environment. If the bandwidth of the testing antenna is very narrow and the mismatch problem is very serious over the required bandwidth, an algorithm is proposed to compensate the mismatch effect so that the obtained radiation pattern and the antenna gain are more accurate. Numerical and experimental results have verified the effectiveness of our method.
2. Hollis, J. S., T. J. Lyon, and L. Clayton, Jr., eds., Microwave Antenna Measurements, Scientific Atlanta, Atlanta, 1970.
3. LO, Y. T. and S. W. Lee, Antenna Handbook, Van Nostrand Reinhold Company, New York, 1988.
4. Johnson, R. C., ed., "Compact ranges," Joint Report of TMAT and IEEE A.P.S., Philadelphia, June 1986.
5. Burnside, W. D., "Dual chamber design reduces quiet zone ripple/ taper errors," Microwave and RF, 168-174, May 1987.
6. Li, H. J., N. H. Farhat, Y. Shen, and C. L. Werner, "Image understanding and interpretation in microwave diversity imaging," IEEE Trans. Antennas Propagate, Vol. 37, No. 8, 1048-1057, 1989.
7. Li, H. J., N. H. Farhat, and Y. Shen, "Image interpretation and prediction in microwave diversity imaging," IEEE Trans. on Geoscience and Remote Sensing, 27, 98-101, 1989.
8. Kiang, Y. W., "Antenna receiving characteristics,", Private note, Department of Electrical Engineering, National Taiwan University.
9. Elliott, R. S., Antenna theory and design, Prentice-Hall, Inc., 1981.