Abstract
This article presents a portable system for freehand antenna diagnosis and characterization based on amplitude-only data. The amplitude-only samples are acquired by moving a handheld probe, which is tracked by a motion capture system, in front of the antenna under test (AUT) aperture. The acquired measurements are processed using the phaseless sources reconstruction method to compute an equivalent current distribution on the AUT aperture. Finally, the radiation pattern of the AUT can be obtained by evaluating the corresponding radiation integrals. Unlike previous work, the use of amplitude-only data avoids the need of a phase reference, paving the way to the diagnosis and characterization of antennas under operational conditions. This fact, together with the handheld capabilities, makes the system very convenient for measurements of already deployed and onboard antennas. Moreover, these amplitude-only acquisitions also simplify the required hardware. The system has been validated through measurements in a wide frequency range from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Ka$ </tex-math></inline-formula> -band up to 300 GHz. Despite that one cannot expect the same degree of accuracy that can be achieved under laboratory conditions (including an anechoic environment and highly accurate positioners), the system shows excellent capabilities to detect malfunctions, such as wrong amplitude/phase distributions, as well as a fair estimation of the far field.
Highlights
A NTENNA diagnosis enables to assess the correct operation of this element
Recent advances demonstrated the feasibility of using freehand systems for antenna diagnosis based on a full acquisition of the field radiated by the antenna under test (AUT) [6], [7]
Once the equivalent currents distribution is computed, the far-field radiation pattern of the AUT can be obtained by means of the corresponding radiation integrals [28], which effectively enable to implement a near-field to far-field (NFFF) transformation
Summary
A NTENNA diagnosis enables to assess the correct operation of this element. In this context, several techniques have been proposed to directly detect faulty elements of an array [1], [2] or to retrieve an equivalent currents distribution [3]–[5] providing more low-level information (e.g., the amplitude and phase of the elements of an array). Recent advances demonstrated the feasibility of using freehand systems for antenna diagnosis based on a full acquisition (amplitude and phase) of the field radiated by the AUT [6], [7] These systems, which can be fastly deployed, avoid the need of using mechanical structures to move the probe antenna. This offers great flexibility since the measurements are acquired at arbitrary positions as the operator of the system moves the handheld probe in front of the AUT aperture without the need of physical constraints This freehand approach is useful for assessing the performance of millimeter-wave (mmwave) antennas and beyond because, at those frequencies, the probe antennas are lightweight and the reflections with the operator are limited.
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