Theory and practice for a spherical-scan near-field antenna range

Thal, H.L.; Manges, John

doi:10.1109/8.1183

Cited by 16 publications

(9 citation statements)

References 5 publications

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“…The mode voltages were computed by a spherical near‐field scan of the electric fields [21, 22] and then transformed to the surface. The scans used 721 and 1081 steps in theta and phi and were done at three probe‐to‐antenna radius ratios (1.050, 1.0625, 1.075) to confirm consistency of the transformed values.…”

Section: Q Validation By Direct Summation Of Stored Energymentioning

confidence: 99%

Effects of loss on the determination of antenna energy and Q

Thal¹

2017

IET Microwaves, Antennas & Propagation

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Expressions for the stored energy and Q factor of an antenna in terms of its radiated spherical modes and reflection coefficient have been extended to include the effects of loss. Three variations are given for excitation by matched, voltage, or current generators, and the importance of the proper phase reference for the radiated fields is emphasised. Two low-Q, selfresonant spherical antennas are used to illustrate the application of the energy formulae with and without loss. The results for these examples are validated by direct integration of the electric energy and by self-consistency of the radiation and dissipation terms. Approximation equations appropriate for processing experimental data are derived, and their predictions are compared with the actual Q's for the examples. Estimates of the lossless Q's are determined from the lossy data.

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Section: Q Validation By Direct Summation Of Stored Energymentioning

confidence: 99%

Effects of loss on the determination of antenna energy and Q

Thal¹

2017

IET Microwaves, Antennas & Propagation

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“…The other N ports are the normalised spherical modes of the radiated far‐zone pattern. The decomposition of an antenna pattern into spherical modes is a well‐documented procedure used for near‐field measurements, for example [15, 16], and pattern analysis. If the modes are defined at a radius R , (5) gives the total stored energy within the sphere defined by R .…”

Section: Stored Energy From Scattering Coefficientsmentioning

confidence: 99%

Antenna Q calculation using radiated modes and reflection coefficient

Thal¹

2015

IET Microwaves, Antennas & Propagation

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Optimisation techniques are currently being used to design antennas with Q values close to theoretical limits. In order to evaluate how closely these designs approach the limits, it is necessary to calculate their Qs from measured or simulated data. Many standard techniques are accurate for large Qs, but yield values significantly below the actual Q for low Q cases. In this study, equations are derived to bracket the actual value of Q, and the issues involved in attempting to determine an exact value are discussed. Both time-averaged and time-varying energies are considered. The derivations and conclusions are different from those previously published. Data from electromagnetic simulations of design examples are used to illustrate.

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“…In these expressions, the functions P |m| n are the associated Legendre functions and h (2) n are the spherical Hankel functions of the second kind.…”

Section: Representation and Calculation Of Coefficients Of A Sphericamentioning

confidence: 99%

“…The topic of a proper truncation mode index N has been discussed previously in the literature, but so far, only the truncation error of the expansion has been taken into account, while the possible errors of the data itself have been ignored. Various empirical and semiempirical rules for N have been given in references [1][2][3]. In an earlier paper by this author [4] analytical expressions for the characteristic modal power distribution and truncation error as a function of N have been derived.…”

Section: Introductionmentioning

confidence: 99%

Reduction of Errors in Antenna Radiation Patterns Using Optimally Truncated Spherical Wave Expansion

Koivisto¹

2004

PIER

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Abstract-This paper demonstrates how the error of a measured or simulated antenna radiation pattern can be decreased by calculating a spherical wave expansion (SWE) with an optimised truncation mode index. Four radiation pattern examples are examined for which the analytical expression of the electrical field is known. Upon adding random and φ-alignment errors to the exact electric fields, the SWEs are determined and compared with the corresponding ones for the exact fields. These comparisons show that the accuracy of the calculated SWE is much better than the accuracy of the original inaccurate field. Resting on the calculated examples, a method is created which can be used to determine the optimal truncation index from the modal power distribution of a SWE without knowing the exact field. Finally, the method developed is applied to measured antenna radiation patterns.

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Theory and practice for a spherical-scan near-field antenna range

Cited by 16 publications

References 5 publications

Effects of loss on the determination of antenna energy and Q

Effects of loss on the determination of antenna energy and Q

Antenna Q calculation using radiated modes and reflection coefficient

Reduction of Errors in Antenna Radiation Patterns Using Optimally Truncated Spherical Wave Expansion

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