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Measurements and Tolerances There are excellent books on measurements, listed below, Thus only special topics pertinent to arrays will be discussed herein. These are: measurement of low sidelobe antennas; array diagnostics; and scan impedance simulators. Because array performance is affected by random errors, tolerances are also discussed in this chapter. A. E. Bailey, Microwave Measurement, IEE/Peregrinus, 1985. 1988. G. H. Bryant, PrincipZe~ of Microwave Measurement, IEE/Peregrinus, G. E. Evans, Antenna Measurement techniques, Artech House, 1990. layton, Microwave Antenna Measurements, Scientific Atlanta, 1970. IEEE Standard Test Procedures for Antennas, Std 149, 1979. 12.1 MEASUREMENT OF. | Phased Array Antennas. Robert C. Hansen Copyright 1998 by John Wiley Sons Inc. ISBNs 0-471-53076-X Hardback 0-471-22421-9 Electronic CHAPTER TWELVE Measurements and Tolerances There are excellent books on measurements listed below. Thus only special topics pertinent to arrays will be discussed herein. These are measurement of low sidelobe antennas array diagnostics and scan impedance simulators. Because array performance is affected by random errors tolerances are also discussed in this chapter. A. E. Bailey Microwave Measurement lEE Peregrinus 1985. G. H. Bryant Principles of Microwave Measurement lEE Peregrinus 1988. G. E. Evans Antenna Measurement Techniques Artech House 1990. J. E. Hansen Spherical Near-field Antenna Measurements lEE Peregrinus 1988. J. S. Hollis T. J. Lyon and L. Clayton Microwave Antenna Measurements Scientific Atlanta 1970. IEEE Standard Test Procedures for Antennas Std 149 1979. 12.1 MEASUREMENT OF LOW-SIDELOBE PATTERNS As mentioned in Chapter 3 the conventional far-field distance of 2Z 2 A is usually inadequate for accurate measurement of patterns with low sidelobes antenna diameter is D. Consider patterns such as the Taylor n. As the observation distance R moves in from infinity the first sidelobe rises and the null starts filling. Then the sidelobe becomes a shoulder on the now wider main beam and the second null rises see Fig. 12.1. This process continues as the distance decreases. To first order the results are dependent only on design sidelobe level. Figure 12.2 shows the distance at which the first sidelobe is raised a given amount for values of SLR from 13 uniform to 60b dB Hansen 1984 . This graph also shows distances at which the first sidelobe is shouldered. Thus the accuracy of measurement may be traded against the measurement distance. 453 454 Amplitude d8 Figure 12.1 Taylor pattern for SLR 40dB n 11. source. Figure 12.2 Sidelobe change vs. normalized measurement distance for Taylor n line ARRAY DIAGNOSTICS 455 Bayliss and .
