Sources Reconstruction Method Research Articles

Improving the Performance of the Phaseless Sources Reconstruction Method for Antenna Diagnostics and Characterization

Improving the Performance of the Phaseless Sources Reconstruction Method for Antenna Diagnostics and Characterization

A Probe Correction Technique for Near Field to Far Field Transform Based on Sources Reconstruction Method

A Probe Correction Technique for Near Field to Far Field Transform Based on Sources Reconstruction Method

Freehand System for Antenna Diagnosis Based on Amplitude-Only Data

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.

In situ antenna diagnostics and characterization system based on RFID and Remotely Piloted Aircrafts

A cost-effective solution for in situ antenna characterization and diagnostics based on Radio Frequency IDentification technology and Remotely Piloted Aircrafts is presented. The cost-effectiveness of the proposed solution is achieved by replacing the radio frequency equipment on-board the small aircrafts with Radio Frequency IDentification tags, while the Antenna Under Test is connected to a Radio Frequency IDentification reader, thus reducing the weight and complexity of the payload of the aircrafts dedicated to antenna measurement task. Received Signal Strength measurements are geo-referred with centimeter-level accuracy thanks to a Real Time Kinematic system. An iterative phase retrieval technique based on the Sources Reconstruction Method is used to recover an equivalent magnetic currents distribution on the Antenna Under Test aperture plane. The reconstructed currents distribution provides antenna diagnostics information and enables the calculation of the antenna radiation pattern. The presented method has been validated by means of measurements in the UHF band for two different antenna arrays with excellent results.

Antenna Diagnostics and Characterization Using Unmanned Aerial Vehicles

This paper presents a compact, low-cost unmanned aerial system for antenna measurement. The proposed system overcomes existing limitations in terms of unmanned aerial vehicle positioning and data geo-referring accuracy using a real-time kinematic positioning system to achieve centimeter-level accuracy. Amplitude-only measurements acquired using a low-cost power sensor are processed by means of the phaseless sources reconstruction method. This is an iterative phase retrieval technique that allows recovering an equivalent currents distribution, which characterizes the antenna under test (AUT). From these equivalent currents, near-field to far-field transformation is applied to calculate the AUT radiation pattern. This contribution also analyzes probe antenna characterization and the impact of positioning and geo-referring accuracy on the radiation pattern. Two application examples of antenna measurement at S- and C-bands using the implemented system are presented.

FAST ANTENNA CHARACTERIZATION USING THE SOURCES RECONSTRUCTION METHOD ON GRAPHICS PROCESSORS

The Sources Reconstruction Method (SRM) is a noninvasive technique for, among other applications, antenna characterization. The SRM is based on obtaining a distribution of equivalent currents that radiate the same field as the antenna under test. The computation of these currents requires solving a linear system, usually ill-posed, that may be very computationally demanding for commercial antennas. Graphics Processing Units (GPUs) are an interesting hardware choice for solving compute-bound problems that are prone to parallelism. In this paper, we present an implementation on GPUs of the SRM applied to antenna characterization that is based on a compute-bound algorithm with a high degree of parallelism. The GPU implementation introduced in this work provides a dramatic reduction on the time cost compared to our CPU implementation and, in addition, keeps the low-memory footprint of the latter. For the sake of illustration, the equivalent currents are obtained on a base station antenna array and a helix antenna working at practical frequencies. Quasi real-time results are obtained on a desktop workstation.

Antenna Diagnostics Using Phaseless NF Information

An extension of the Sources Reconstruction Method (SRM) for antenna diagnostics using phaseless information is presented. The aim of this work is to extend the method's capabilities from planar field acquisition domains to arbitrary ones. To achieve this goal, the SRM capabilities for handling arbitrary-geometry domains are combined with phase retrieval technique. The consideration of the radiation inverse problem with a general integral equation formulation using arbitrary-geometry field and currents domains, and field phaseless information, supposes a challenging ill-posed problem that is solved using iterative minimization techniques for non-linear problems. An application example is presented, comparing the proposed method's performance with amplitude and phase results.

CHARACTERIZATION OF ANTENNA INTERACTION WITH SCATTERERS BY MEANS OF EQUIVALENT CURRENTS

Antenna characterization in presence of obstacles requires removing multipath efiects in order to retrieve the non-distorted antenna radiation pattern. In this contribution a new approach based on the Sources Reconstruction Method is proposed. The idea is to characterize the Antenna-Under-Test (AUT) and the region where the scatterers are located through a set of equivalent currents. Finally, the reconstructed equivalent currents on the contour enclosing the AUT can be used to recover the AUT radiation pattern, removing most of the distortion efiect due to the presence of the scatterers.

The Sources Reconstruction Method for Amplitude-Only Field Measurements

An extension of the sources reconstruction method (SRM) for antenna diagnostics using amplitude-only field measurements is presented. While previous works limit the application to canonical domain cases, the combination of the SRM capabilities for handling with arbitrary-geometry domains jointly with phase retrieval techniques, allows antenna diagnostics extension to complex geometry antenna and field acquisition domains. The consideration of the radiation inverse problem with a general integral equation formulation using arbitrary-geometry field and currents domains, and field phaseless information, supposes a challenging ill-posed problem that is solved using iterative minimization techniques for non-linear problems. Different examples are presented, from simple to general antenna diagnostics cases.

Geometry Reconstruction of Metallic Bodies Using the Sources Reconstruction Method

This letter presents a novel application of the Sources Reconstruction Method (SRM) for geometry reconstruction. Foundations of this work are based on the correspondence between the placement of the metallic objects and the highest values of the reconstructed equivalent currents. In order to improve the accuracy of the method, reconstructed equivalent currents, due to different incident waves and working frequencies, are combined. Application examples using simulated data are presented.

On the sources reconstruction method application for array and aperture antennas diagnostics

AbstractThis article presents two practical applications of the Sources Reconstruction Method for antenna diagnostics and antenna manufacturing errors detection. The goal is to show the SRM capabilities to determine defective elements in antenna arrays as well as to detect irregularities in the surface of reflector antennas from the analysis of the aperture fields. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1664–1668, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24416

Antenna Diagnostics Using Arbitrary-Geometry Field Acquisition Domains

An extension of the sources reconstruction method (SRM) for handling with arbitrary-geometry field acquisition domains is presented. The amount of information that is needed to retrieve the original sources (field-sampling requirements, number of field components to be considered) is discussed as well as the influence of the noise in the measurements and the resolution limitations. The discussion is supported by a numerical simulation using a cubic field acquisition domain.

Probe-distortion correction for the sources reconstruction method

This paper introduces a probe-correction method for near-field antenna measurements. The proposed technique is intended to be used jointly with a sources reconstruction method for antenna diagnosis and near-field-to-far-field (NF-FF) transformation. The method is based on the introduction of the probe antenna's pattern as a weighting function into the field integral equations relating the measured near field and the antenna's equivalent sources. In this way, the equivalent currents are reconstructed without distortion due to the probe's pattern, as well as the fields calculated from those currents. The theoretical formulation and practical examples based on antenna measurements are presented in this paper.

On the Comparison Between the Spherical Wave Expansion and the Sources Reconstruction Method

A comparison between two well-known near field to far field (NF-FF) transformation methods is presented: the spherical wave expansion (SWE) and the sources reconstruction method (SRM). The goal of this paper is to show the methods performance for NF-FF transformation pointing out the advantages and limitations of each one. First, the computational cost is studied, showing its dependence with the antenna under test (AUT) electric size. Second, the NF-FF transformation accuracy of each method is compared for a fixed AUT electric size, analyzing also the influence of the main parameters that affect the SRM and SWE accuracy. Third, the SRM capabilities are presented, with focus on the NF-NF transformation inside the minimum sphere. Practical applications of the SWE and SRM are illustrated by means of an example of NF-FF transformation and antenna diagnostics problem using measured NF data.