Near-Field Electromagnetic Measurement Techniques

Near-field electromagnetic measurement techniques probe the region immediately around radiating structures, where reactive and radiative field components coexist. By scanning a dedicated probe across a predefined measurement aperture, spatial distributions of the electric and magnetic field vectors can be acquired with subwavelength resolution. These measurements support accurate antenna characterisation, electromagnetic compatibility testing and inverse-source reconstruction. Core methods include planar, cylindrical and spherical scanning geometries, each offering trade-offs between coverage, measurement speed and complexity of data processing. Transformations from measured near-field data to far-field radiation patterns rely on non-redundant sampling strategies and mathematical transforms that minimise data acquisition time while preserving accuracy. Recent advances have focused on probe design innovations, spatial warping of sampling grids to reduce measurement points, and enhanced inversion models that stabilise equivalent source extraction. Such developments reinforce the global importance of near-field techniques for next-generation wireless systems, high-precision radar sensors and non-destructive evaluation of materials.

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Near-Field Electromagnetic Measurement Techniques publication trend

The graph below shows the total number of articles in near-field electromagnetic measurement techniques across all publications each year (not limited to Nature Index journals).

Technical terms

Near field: The region within approximately one wavelength of a radiating structure where reactive and radiative field components overlap.

NF–FF transformation: A mathematical procedure converting measured near-field data into far-field radiation patterns.

Sampling theorem: A principle ensuring that a band-limited continuous field can be fully reconstructed from discrete samples taken at or above a critical spacing.

Equivalent dipole source: A simplified representation of a radiating system using discrete dipoles whose strengths are determined from measured field data.

Warping transformation: A spatial change of variables applied to the measurement aperture to yield non-uniform sampling grids that optimise data acquisition.

References

1. Application of Nonredundant Sampling Representations of Electromagnetic Fields to NF‐FF Transformation Techniques. International Journal of Antennas and Propagation (2012).
2. Design and characterisation of a dual probe with double‐loop structure for simultaneous near‐field measurement. IET Microwaves, Antennas & Propagation (2022).
3. Efficient Planar Near-Field Measurements for Radiation Pattern Evaluation by a Warping Strategy. IEEE Access (2021).
4. An Improved Equivalent Dipole Moment Source Model Based on Regularization Optimization Method for Near Field-Far Field Conversion. IEEE Access (2020).