A Cylindrical Near-Field vs. Spherical Near-Field Antenna Test Comparison

Author: Jeffrey Fordham

A new series of spherical near-field probe positioning devices has been designed and constructed consisting of a large 5.0 meter fixed arc. Several of these large radius arc systems have been developed for telematic antenna testing, radar antenna and ground based communication systems test.

As part of the delivery of one of these spherical near-field (SNF) test systems, a measurement study was performed to determine the accuracy of the new facility relative to an existing cylindrical near-field (CNF) test facility. The study was conducted by collecting and processing data on an offset fed parabola reflector antenna both on the CNF range and on the SNF antenna test range.

This article summarizes the results obtained as part of the measurement program and includes discussions on the error budgets for the two ranges along with a discussion on the mutual error budget between the two ranges.

 

A Composite Near-Field Scanning Antenna Range for Millimeter-Wave Bands

Authors: Doren W. Hess, John McKenna, Steve Nichols

This paper describes a Composite Near-Field Scanning Antenna Range for frequency bands that extend from X-Band in the microwave frequency regime through W-Band in the millimeter-wave regime – i.e. 8.2 through 110 GHz. We show some of the initial checkout data using pyramidal standard gain horns and compare the patterns to theory.

 

A Low Cost and High Accuracy Optical Boresighting and Alignment System Using Video Cameras

Authors: John Demas, Quy Phan

This paper describes a novel optical boresighting and alignment system used to mechanically align antennas on a compact antenna range at the North Island Naval Air Depot in San Diego, CA. The antenna range has a 5-axis (roll/upper slide/azimuth/elevation/lower slide) positioner used to measure various airborne antennas for production testing. The video alignment system implemented on this range uses two video cameras outfitted with telephoto lenses, one on the roll stage and the other on an antenna-mounting fixture. The system has been demonstrated to yield an accuracy of ±0.005 degrees. Prior to the start of testing the positioner is commanded to a “0” position and the cameras focus on a fixed optical target to provide the operator with a quick visual confirmation that the positioner is accurately aligned prior to testing. The video alignment system described has numerous advantages over other mechanical alignment techniques, is low cost, easy to use, and can be adapted to a variety of testing configurations.

 

A Powerful Alternative for High Speed Near-Field of Far-Field Antenna Measurements

Author: David S. Fooshe

A high speed receiver and beam controller has been introduced to address the growing need for faster antenna measurements. This article describes the Panther 6000 system and will show how it can benefit the antenna range operator by allowing more complex CW and pulsed antennas to be tested in less time.

Many of today’s high performance antennas are broadband, multi-beam, multi-port and polarization-selective devices. Technology improvements, including micro-electro-mechanical system (MEMS) devices and novel adaptive algorithms, are enabling increasingly complex antennas for satellite communications, radar, telecom, wireless and automotive applications. New and complex architectures are also being implemented, including adaptive arrays, multiple-reflector and digital beamforming antennas.

 

A Reflectometer for Antenna Measurements

Authors: John McKenna, David M. Kokotoff, Bjorn Widenberg

The reflection coefficient of an antenna impacts the power transmitted by the antenna. Accurate characterization of this parameter is important in a communication or radar system. This paper discusses an implementation whereby a reflectometer is located near the antenna under test in an antenna range albeit far from the receiver. By placing the reflectometer near the antenna, the measurement uncertainty intrinsic to long cable runs can be minimized.

 

An Automated Cylindrical Near-Field Measurement and Analysis System for Radome Characterization

Authors:Matthew Giles, Shantnu Mishra, Ph.D.

The David Florida Laboratory (DFL) was contacted by the Canadian Department of National Defense (DND) to develop an accurate, reliable, more cost effective method of characterizing existing nose cone mounted radomes for the radar systems aboard aircraft such as CF-18. Traditionally, these measurements have been performed in a far-field (FF) range using conventional positioning and measurement systems and specialized instruments such as a null seeker. Recently, the use of near field methods has been incorporated in radome measurement practices. This paper describes one such adaptation of a cylindrical near-field facility (CNF) for radome measurements.

 

An Efficient and Highly Accurate Technique for Periodic Planar Scanner Calibration with the Antenna Under Test in Situ

Authors:Scott Pierce, Marion Baggett

This paper describes the development, testing and evaluation of a new, automated system for calibration and AUT alignment of a planar near-field scanner that allows the calibration system to remain in place during AUT measurement and which can be used to support AUT alignment to the scan plane. During scanner calibration, probe aperture position measurements are made using a tracking laser interferometer, a fixture that positions the interferometer retro reflector at a precise location relative to the probe aperture and a probe roll axis that maintains the proper orientation between the retro reflector and the interferometer as the probe position is moved. Aperture scan path information is used to construct a best-fit scan plane and to define a Cartesian, scanner-based coordinate system. Scan path data is then used to build a probe position error map for each of the three Cartesian coordinates as a function of the nominal position in the scan plane. These error maps can be used to implement software-based corrections (K-corrections) or they may be used for active Z-axis correction during measurements. By using a set of tooling points on the antenna mount, an AUT coordinate system is measured with the interferometer. The system then directs an operator through a set of AUT adjustments that align the AUT with the planar near-field scanner to a desired accuracy. This paper describes the implementation and testing of the system on an actual planar scanner and AUT test environment, showing the improvement in effective scanner planarity.

 

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