Abstract
This article presents a thorough study of spherical probe-corrected phaseless near-field measurements with the two-scans technique. Such technique is based on retrieving the antenna under test radiation pattern from the measurement of the near-field amplitude signals on two spheres of different radii. The postprocessing of this type of measurements results in a highly nonlinear algorithm, prone to get trapped in local minima and provide incorrect solutions when the measurement conditions are not properly selected. Through a series of numerical simulations, the influence of different measurement parameters on the phaseless technique is analyzed. It will be shown how both the relative and absolute values of the measurement spheres highly affect the convergence of the phase retrieval algorithm. The type of AUT and its radiation pattern characteristic also play a fundamental role in the feasibility of phaseless measurements. Other parameters such as sampling rate, noise, probe correction, polar truncation, and measurement offsets are also investigated. The conducted study allows to extract a set of guidelines to improve the accuracy of phaseless spherical near-field algorithms. In addition, purely phaseless antenna measurement examples are given to demonstrate the algorithm capabilities and limitations, and to validate the developed numerical investigations.
Highlights
SPHERICAL near-field measurements [1]-[3] are a wellstablished technique for antenna testing
Separation between Huygens sources is set to 0.1λ forming a uniform grid, while the number of them and its amplitude and phase distribution will be adjusted according to the different experiments
The lower plot shows how the retrieved solution is degraded as the array aspect ratio changes in the rectangular arrays, reaching to the point that the algorithm gets trapped in a local minimum for all values of r when the Antenna Under Test (AUT) is a linear array
Summary
SPHERICAL near-field measurements [1]-[3] are a wellstablished technique for antenna testing. From the different phaseless techniques, those based on multiple scan surfaces constitute an attractive alternative because they can be implemented in traditional measurement setups without any hardware modification This led to the development of the two-scans planar [16]-[19] and spherical [20]-[22] techniques, in which the AUT radiation pattern is extrapolated from the measurement of near-field intensities over two planes or two spheres, respectively. No a priori knowledge about the AUT is required apart from its minimum sphere In this sense, the two-scans spherical technique has been comparatively less studied, but it has been applied to sophisticated antennas showing low transformation errors and promising capabilities [21].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
