1995 Technical Papers

A Portable 4.5m X 2.0M Near-Field Scanner

Author: David S. Fooshe
Publication: AMTA 1995
Copyright Owner: NSI-MI Technologies

Portable scanners used for near-field antenna measurements are usually incapable of providing a large scan area with a high degree of probe position accuracy. This paper discusses a 4.5m x 2.0m portable scanner developed by NSI with a probe position accuracy on the order of 2 mils (0.050 mm) rms. An NSI patented optical measurement system measures the X, Y, and Z position, and provides real-time position correction capability. This lightweight, portable scanner combined with optical correction provides enhanced accuracy while reducing overall antenna measurement system costs and improving test chamber flexibility.


Hologram Accuracy Estimation

Author: Gregory F. Masters
Publication: AMTA 1995
Copyright Owner: NSI-MI Technologies

Hologram measurements are becoming more and more popular as a reliable method for identifying bad elements and the tuning of active phased array antennas. Relying on holographic data to adjust phase shifters and attenuators in these antennas can give undesired results if the accuracy of the data is poor. Often measurements can be improved if the error sources can be isolated and quantified. This paper presents an approach to producing a hologram accuracy budget based on the NIST 18-term error budget created for near-field measurements. A set of hologram accuracy terms is identified and data is presented showing the typical hologram accuracy that can be expected from a near-field scanner.


State-of-the-art Near-field Measurement System

Author: Karl Haner, Greg Masters
Publication: AMTA 1995
Copyright Owner: NSI-MI Technologies

Planar near-field measurements are the usual choice when testing phased array antennas. NSI recently delivered a large state-ofthe- art near-field measurement system for testing a multi-beam, solid state phased-array antenna. The critical sidelobe and beam pointing accuracy specifications for the antenna required that special attention be paid to near-field system design. The RF path to the moving probe was implemented using a multiple rotary joint system to minimize phase errors. Additional techniques used to minimize system errors were an optical probe position correction system and a Motion Tracking Interferometer (MTI) for thermal drift correction.


2095P Pulsed Microwave Measurement System for the Naval Surface Warfare Center, Crane Division

Author: R. S. Sauerman
Publication: AMTA 1995
Copyright Owner: NSI-MI Technologies

Modem pulsed phased array radar systems bring new challenges to antenna measurement. These antennas generally consist of hundreds of Transmit-Receive (TR) modules controlled via a beam steering computer to fonn the antenna beam. Attempting to operate these modules with a CW wavefonn will not only quickly damage the modules but will not properly characterize the antenna. The Navel Surface Warfare Center, Crane Division, recognized the need to add pulsed capability when specifying their latest antenna measurement system. Scientific Atlanta met these requirements by integrating their newly introduced Model 1795P Pulsed Microwave Receiver into their proven 2095 Microwave Measurement System to make the Model 2095P Pulsed Microwave Measurement System.


A Multi-Purpose Large Compact Range for Antenna, Spacecraft Payload, and RCS Measurements

Authors: John R. Jones, C. Lee Allen, and Ed Hart, Juan-Luis Cano, Pablo Garcia-Mueller
Publication: AMTA 1995
Copyright Owner: NSI-MI Technologies

Compact ranges have found wide application for antenna measurements, RCS measurements, and, most recently, for spacecraft payload measurements. Each of these applications requires certain special features of the range optics, positioning systems, electronics, and software. The system design of a compact range measurement sys­tem for making all these types of measurements presents a number of challenges.

This paper will discuss the system aspects of the design of a multi-purpose compact range facility. Items of interest include the RF electronics design, the positioning system design, the optimization of the reflector and feeds and the specialized software design.


A Triband Radome Measurement System Installation and Testing Results

Authors: Virginia V. Jory, John R. Jones, Victor R. Farr, Sidney J. Manning, Luis L. Oh, George W. Pearson, T. Larry Norin
Publication: AMTA 1995
Copyright Owner: NSI-MI Technologies

In an earlier paper ("System Engineering for a Radome Test System," John R. Jones, et al, AMT A, October 1994) the system level design of a compact range enhancement for the testing of the Triband Radome was presented. This paper will discuss the installation and testing of the radome measurement system in the compact range. The purpose of the radome measurement system is to determine (within close tolerances) boresight shift, transmission loss, antenna pattern changes and polarization effects caused by the radome. Unique features include novel coordinate transformation and correction by means of a laser autocollimator and data reduction algorithms. Also featured is the tracking subsystem which consists of a specially designed two-axis track pedestal, an autotrack controller, and three five-horn compact range feed arrays operating at X, K, and Q-bands. The performance of the triband radome measurement system in the compact range setting will be presented.



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