This single volume provides a comprehensive introduction and explanation of both the theory and practice of all forms of modern antenna measurements, from their most basic postulates and assumptions to the intricate details of their application in various demanding modern measurement scenarios. Theory And Practice Of Modern Antenna Range Measurements begins with an initial examination of the properties of antennas that allow them to enhance the free space interaction of electronic systems, followed by an introduction to direct far-field measurements. The text presents a comprehensive treatment of Compact Antenna Test Ranges, Body-Centric measurements, and detailed developments of standard planar, cylindrical and spherical near-field techniques. Detailed discussions are also provided on near-field range error budgets which are an indispensable part of antenna metrology. The book concludes with some of the most recent advances in the various measurement techniques including aperture diagnostics, phase-less antenna metrology, error correction, range multi-path suppression techniques, and gain measurements. Extensive examples illustrate the concepts and techniques. A large number of antenna test facilities exist worldwide but to the authors' knowledge no single text provides a clear step-by-step description of all the details of the Planar, Cylindrical, Spherical Near-Field, Compact Range and Body-centric Measurement Techniques. All four authors have spent a significant proportion of their professional careers involved with antenna measurements and the aim of this text is to provide the reader with a complete, coherent, comprehensive and practical text that will act as a single reference for all aspects of modern antenna measurements.
Inspec keywords: mobile antennas; electromagnetic field theory; antenna testing
Other keywords: body-centric antenna measurements; antenna coupling; compact range measurements; electromagnetic theory; near-field antenna measurements; mobile antenna measurements
Subjects: Electric and magnetic fields; General electrical engineering topics; Antennas; Production facilities and engineering
This text concerns itself with the 'theory and practice of modern antenna range measurements' and as such it is intimately concerned with the problem of the quantification, interpretation and verification of a range of physically observable phenomena that, as will be described in this text, are associated with the emission, reception and scattering of electromagnetic waves. More specifically the technologies and concepts to be discussed and explained in the text along with their use in engineering situations are bounded by a range of frequencies that are normally referred to as micro and/or sub-millimetre wave (10 MHz to 1 THz frequency range).
In this text, while attempting to explain the observed phenomena of antenna coupling in terms of the underlying electromagnetic mechanisms, all discussion of the electromagnetism will be confined to the classical representations of field concepts. This is usually sufficient for extended macroscopic objects like platforms, targets, transmission lines and antennas, the main categories of assets that are of concern in antenna and RF engineering. However, it should be borne in mind that all scientifically based theories have a range of applicability including classical EM theory, and although more accurate relativistic gauge theories of the EM interaction will not be addressed in this text, as antenna theory concerns the propagation of electromagnetic energy between physically remote antennas at the speed of light, it will not be possible to completely ignore the relativistic aspects of antenna theory.
Although the practical use of antennas is mainly in an outdoor environment where there are large separations between Tx and Rx antennas, modern antenna test ranges attempt to make measurements in indoor facilities where TX and Rx antenna are in close physical proximity to each other. Such indoor facilities have the advantages of security, control of the environment and ease of access for equipment and personnel. However, in order to make measurements in indoor facilities that mirror what would be expected on large outdoor ranges, a number of engineering solutions are required. These solutions involve isolating the test range from its immediate environment, which usually involves placing the range in a metallic chamber of some other enclosure to ensure the signals generated inside the chamber stay in the chamber and signals generated outside the chamber do not interfere with the measured signals generated inside the chamber.
This chapter discusses the various compact antenna test range (CATR) reflector measurements on comment on their main design issues.
This chapter discusses the so-called planar near-field antenna test range. This implies that the planar near-field range is only a useful tool if it is used for highly directive antennas where it can be assumed that by far the vast majority of the radiated power is incident on the plane over which the data is sampled.
This chapter has presented a development of the standard probe-corrected cylindrical near-field antenna measurement theory. The great advantage of the cylindrical approach is that it is instantly applicable to testing antennas for which it is desired to compute the complete 360o far-field azimuthal pattern. However, for the class of antennas that do not satisfy this directivity requirement, recourse must be sought in spherical near-field antenna testing which is developed.
From the material presented here, it is clear that the theory underlying the SNF approach is complex and involved to implement. However, it is also very elegant and provides one with many measurement options and powerful capabilities. The numerical implementation of the theory can be efficiently deployed through the use of the fast Fourier transform (FFT) enabling transforms of even electrically large antennas to be accomplished in a matter of a few seconds on a modern powerful digital computer. With the advent of commercially available SNF test systems, the user can exploit these techniques, largely unimpeded by the burden of the theory or the implementation thereof. The material presented here highlighted some of the fundamental concepts and limitations the user needs to be aware of in order to use these test systems with confidence.
The uncertainty concepts described in this chapter form the basis of any range assessment (RA), regardless of the type of test facility and therefore allow us to create a framework within which the quality of any antenna measurement result can be expressed. It also allows us to do meaningful range inter-comparisons that have become such an integral part of modern test programmes. Although most of the groundwork related to RAs was conducted in an effort to validate near-field testing in the early days, this work has found wider application and can today be applied to far-field and CATR test systems with equal success. It is safe to say that the antenna measurement community (for the most part) have adopted the principle that measurement results need to be reported with an associated uncertainty, to make them credible.Finally, a very welcome side effect of doing any RA is a greater understanding of the measurement process and associated weaknesses. This often leads to a clear definition of exactly what aspect needs to be addressed if uncertainty is to be reduced, making for a very efficient use of resources in the process.
In this chapter we look at the key issues that are unique to the measurement of this class of antenna, and we start by considering both far-field and near-field techniques for radiation pattern measurement. We then consider the measurement of return loss and hence the antennas' operating bandwidth. In the practical use of mobile devices, there are no RF cables connecting them, but for S-parameter and pattern measurements a cable usually exists and it can have significant influence on the resulting measurements, and in section 9.5 we show how the use of optical fibre connections is solving this problem. The human body has a high dielectric constant and so antennas mounted close to the body operate differently than in 'free space', so in section 9.6 we consider the issue of 'on-body' antenna measurements both on a live subject and on the use of phantoms. For electrically small antennas efficiency is very important and in section 9.7 we consider the measurement of efficiency via both radiation pattern measurement and the Wheeler Cap method, where we report an improved method well suited to body-centric measurements. Finally we consider the measurement of UWB antennas, noting that 'radiation pattern' has less importance than pulse fidelity in many UWB applications.
This chapter encompasses a number of disparate antenna measurement topics: open-ended rectangular waveguide probes; dual polarised waveguide probes; broadband probes; far-field anechoic chamber measurements; probe calibration; channel balance correction for measurements of linearly and circularly polarised antennas; aperture diagnostics; amplitude and phase drift correction; antenna pattern rotation; alignment correction in planar antenna measurements; antenna pattern correction; near-field antenna measurements; planar and cylindrical mathematical absorber reflection suppression; spherical near-field electrical alignment; and three antenna gain method.
Appendices are presented for: radar bands IEEE standard letter designations, rectangular waveguide bands, microwave coaxial connectors, coordinate systems and their isometric rotation, antenna measurements, reflection coefficients, return loss, transmission loss, polarisation basis.