33m by 16m Near-field Measurement System

Authors: Terrance Speicher, Sevtap Sapmaz, Michiharu Niwata
Publication: AMTA 1998
Copyright Owner: NSI-MI Technologies

Nearfield Systems Inc. (NSI) has delivered the world’s largest vertical near-field measurement system. With a 30m by 16m scan area and a frequency range of 1GHz to 50GHz, the system consists of a robotic scanner, laser optical position correction, computer and microwave subsystems. The scanner and microwave equipment are installed in an anechoic chamber 40m in length by 24m in width by 25m in height. The robotic scanner controls the probe positioning for the 33m by 16m vertical scanner using X, Y, Z and polarization axes. The optical measurement package precisely determines the X and Y axes position, alignment errors along the X and Y axes, and Z-planarity over the XY scan plane.


Design And Validation Of A General Purpose Near-Field Antenna Measurement Facility For The Royal Netherlands Navy

Authors: Mart Hagenbeek, Daniël Janse van Rensburg
Publication: AMTA 1998
Copyright Owner: NSI-MI Technologies

This paper describes a new multi-purpose planar & cylindrical near-field antenna test facility installed at the Royal Netherlands Navy (RNN). In this paper an overview is given of the initial list of requirements that was generated and the process of selecting the best type of measurement facility to address these. A description of the facility is given and an outline of the accuracy of the planar/cylindrical near-field scanner is presented. The paper contains details of the extensive validation program and measured data demonstrating the performance of the system.


Phased-Array Simulation For Antenna Test Range Design

Author: Daniël Janse van Rensburg
Publication: AMTA 1998
Copyright Owner: NSI-MI Technologies

A simulation tool used during the design of nearfield ranges for phased array antenna testing is presented. This tool allows the accurate determination of scanner size for testing phased array antennas under steered beam conditions. Estimates can be formed of measured antenna pointing accuracy, side lobe levels, polarization purity, and pattern performance for a chosen rectangular phased array of specified size and aperture distribution. This tool further allows for the accurate testing of software holographic capabilities.


Precision Boresight Measurement for Doppler Radar

Authors: Vern Moore, Bert Schluper
Publication: AMTA 1998
Copyright Owner: NSI-MI Technologies

Airborne Doppler Velocity Sensors require precise boresight information in determining a Doppler solution. Far-field ranges have been extensively used to provide this boresighting capability. This paper discusses an empirical investigation to determine the feasibility of using near-field techniques to fulfill the boresighting requirement.


Probe Correction Effects On Planar, Cylindrical And Spherical Near-Field Measurements

Authors: Greg Hindman, David S. Fooshe
Publication: AMTA 1998
Copyright Owner: NSI-MI Technologies

The accuracy of the probe antenna pattern used for probe-corrected near-field measurements is critical for maintaining high accuracy results. The probe correction is applied differently in the three standard near-field techniques – planar, cylindrical, and spherical. This paper will review the differences in sensitivity to probe correction for the three techniques and discuss practical aspects of probe correction models and measurements.


Quantifying The Effect Of Position Errors In Spherical Near-Field Measurements

Authors: Allen C. Newell, Greg Hindman
Publication: AMTA 1998
Copyright Owner: NSI-MI Technologies

Concise mathematical relations have been derived for Planar Near-Field measurements that quantify the effects of x, y and z-position errors on antenna parameters such as gain, sidelobe level, pointing, and cross polarization. Because of the complexity of the theory, similar relations for spherical near-field measurements have not been developed. The requirements for the spherical coordinate system are generally defined in terms of the alignment parameters such as orthogonality and intersection of axes, θ-zero, xzero and y-zero rather than individual errors in θ, φ and r. Mechanical, optical and electrical techniques have been developed to achieve these alignments. This paper will report on the development of methods to estimate the antenna parameter errors that will result from spherical alignment errors for typical antennas.


Spherical Coordinate Systems For Defining Directions And Polarization Componets In Antenna Measurements

Author: Allen C. Newell
Publication: AMTA 1998
Copyright Owner: NSI-MI Technologies

The results of theoretical calculations or measurements for antennas are generally given in terms of the vector components of the radiated electric field as a function of direction or position. Both the vector components and the direction parameters must be defined with respect to a coordinate system fixed to the antenna. Along the principal planes there is no ambiguity about the terms such as vertical or horizontal component, but off the principal planes the definition of directions and vector components depends on how the spherical coordinate system is defined. This paper will define four different spherical coordinates that are commonly used in measurements and calculations, and propose a terminology that is useful to distinguish between them, and define the mathematical transformations between them. These concepts are essential when the results of different measurements or calculations are compared or when an antenna’s orientation is changed. Both mathematical and graphical representations will be presented.



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