550 Ghz Near-Field Antenna Measurement System for NASA Submillimeter Wave Astronomy Satellite

Author: Dan Slater
Publication: AMTA 1994
Copyright Owner: NSI-MI Technologies

This paper describes a 550 GHz planar near-field measurement system developed for flight qualification of the radio telescope carried onboard the NASA submillimeter wave astronomy satellite (SWAS). The very high operating frequency required a new look at many near-field measurement issues. For example the short wavelength mandated a very high precision scanner mechanism with an accuracy of a few microns. A new thermal compensation technique was developed to minimize errors caused by thermally induced motion between the scanner and spacecraft antenna.

 

A Low Cost Spherical Near-Field System

Author: Jeff Way, Karl Haner
Publication: AMTA 1994
Copyright Owner: NSI-MI Technologies

The Spherical Near-Field measurement technique has been in existence for a number of years. The cost associated with this type of measurement system has often been assumed to be substantial. Herein is presented the system configuration for a low cost Spherical Near-field System whose design goals include the capability for production line testing while retaining simplicity in approach. NSI has been contracted to provide a Spherical Near-field antenna measurement system. This paper focuses upon the design considerations undertaken during the prototype development of that system.

 

An Integrated Near-field EMC Measurement System

Author: Dan Slater
Publication: IEEE EMC Conference 1994
Copyright Owner: IEEE

This paper briefly describes the theory and application of a small near-field imaging system designed for EMC precompliance applications. This system produces EMI and EMS images of circuit cards, cables and related items. If extended by using a phase coherent receiver in a region of free space propagation, this same system can precisely measure the radiation pattern of directive antennas and image the multipath within an anechoic chamber or TEM cell.

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Anechoic Chamber Evaluation

Author: Karl Haner
Publication: AMTA 1994
Copyright Owner: NSI-MI Technologies

This paper details the evaluation of a major aerospace company's tapered anechoic chamber. Using an NSI 3' x 3' near-field scanner and software, the chamber was evaluated at 11 frequencies and two polarizations. SAR imaging techniques were used to map the chamber reflections. A new addition to the software provided the ability to map the difference between the measured phase front and the theoretical spherical phase front; the software also derives the x, y, and z phase centers of the source. Error estimates for all aspects of the evaluation will be discussed.

 

Position Correction on Large Near-Field Scanners Using an Optical Tracking System

Author: Greg Hindman
Publication: AMTA 1994
Copyright Owner: NSI-MI Technologies

Large scanners used for near-field antenna measurements require careful attention to the design and fabrication process to maintain probe position accuracy1. This paper discusses the design, implementation, and results of a novel optical probe position tracking system used by NSI on a number of large near-field scanners. This system provides measurement of the probe X, Y and Z position errors, and real-time on-the-fly position correction. The use of this correction can significantly enhance measurement accuracy, and can reduce the cost of building large near-field scanners.

 

System Engineering for a Radome Test System

Author: John R. Jones, Virginia V. Jory, David R. Smith, Doren W. Hess, Jr., A. Reneé Soster, Alan L. Wilcox
Publication: AMTA 1994
Copyright Owner: NSI-MI Technologies

This paper will discuss the system level design of a radome test system implemented in a compact range. The system includes a tracking pedestal controlled by an autotrack controller, a measurement receiver, a unique five-feed arrangement for the compact range which accommodates both tracking and measurement functions, and a laser autocollimator for coordinate system referencing. Key elements of system design include the required coordinate system transformations, the mechanical design of the positioning system and its contribution to the tracking system, and the synchronization of the autotrack controller, the measurement receiver, and the autotrack controller, the measurement receiver, and the system controller. There aspects of system design will be discussed and measurement and analysis results will be presented.

 

Three Antenna Gain Method on a Near-Field Range

Author: W.G. Scott, G.F. Masters
Publication: AMTA 1994
Copyright Owner: NSI-MI Technologies

The Three-Antenna gain method is commonly used on far-field ranges to determine an antenna’s absolute gain. This is especially true when no other calibrated antenna is available. This method has been used for years by calibration laboratories such as NIST to calibrate probes and gain standards for far and near-field ranges. In some cases the calibration is too costly or does not meet the schedule requirements of the near-field test range. An alternative is to calibrate the probe or gain standards directly on the near-field range. In this paper we present the results of a study done to show the accuracy of the Three-antenna gain method when used on a near-field range. An extensive error analysis is presented validating the utility of this method.

 
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