1999 Technical Papers

An Introduction to Antenna Test Ranges, Measurements and Instrumentation

Authors: Jeffrey A. Fordham

Publication: Antenna Systems and Technology

Copyright Owner: NSI-MI Technologies

By definition, all of today’s wireless communication systems contain one key element, an antenna of some form. This antenna serves as the transducer between the controlled energy residing within the system and the radiated energy existing in free space. In designing wireless systems, engineers must choose an antenna that meets the system’s requirements to firmly close the link between the remote points of the communications system. While the forms that antennas can take on to meet these system requirements for communications systems are nearly limitless, most antennas can be specified by a common set of performance metrics Each of these characteristics are evaluated using a suitable antenna test range.

Completion of a Satellite Antenna Test and Repair Facility Relocation

Authors: Thomas Ondrey, Doug Kremer, Vicki Garcia, Joseph Friedel, Robert Keyser

Publication: AMTA 1999

Copyright Owner: NSI-MI Technologies

The maintenance, test, and repair workload for the Air Force’s AN/MSQ-118 satellite ground-based receiving communication system has been transferred from the closing McClellan Air Force Repair Facility in Sacramento, California to Tobyhanna Army Depot located in Tobyhanna, Pennsylvania. The workload requires the support of four maintenance shops and two planar near-field ranges. The shops are the antenna repair, power supply repair, low-noise amplifier (LNA) repair, and radome repair shops. The near-field ranges are a 4’ x 4’ planar scanner used for antenna diagnostics and an 8’ x 8’ planar scanner used for certification of the repaired antenna-under-test (AUT).

This paper will bring the AMTA community up to date on the status of the new Tobyhanna Antenna Repair Facility, focusing on the techniques and methods used to quantify the alignment and performance characteristics of the planar near-field antenna measurement system used for certification. With the relocation complete, test data obtained at both locations will be analyzed and compared to show differences between the baseline measurements taken at McClellan Air Force Base versus those taken at Tobyhanna Army Depot.

High Accuracy Cross-Polarization Measurements using a Single Reflector Compact Range

Authors: Christopher A. Rose, James H. Cook, Jr.

Publication: AMTA 1999

Copyright Owner: NSI-MI Technologies

MI Technologies has developed a technique to achieve very high accuracy cross-polarization measurements using a single reflector compact range. The technique, known as the "Error Correction Code Algorithm" (ECCA) leverages the "ideal" performance of a single parabolic reflector when the feed axis is aligned to the parabola axis. ECCA mathematically corrects for the amplitude taper induced by the feed axis alignment.

Historically, ‘conventional’ compact range polarization purity has been limited to »-30 dBi. The ECCA technique, however, lowers the cross-polarization error to »-48 dBi. This performance has been verified in two separate inter-range measurement comparisons with the National Institute of Standards and Technology. The results of these tests prove ECCA is an extremely accurate technique for low cross-polarization measurements and provides a lower cost, superior performance alternative to dualreflector systems when low cross-polarization measurements are required.

Low Cross-Polarized Compact Range Feeds

Authors: Jeffrey A. Fordham, James H. Cook, Jr.

Publication: AMTA 1999

Copyright Owner: NSI-MI Technologies

Compact antenna test ranges intended for low crosspolarization antenna measurements require the use of feeds with polarization ratios typically greater than 40 dB across the included angle of the quiet zone as well as across the frequency band of interest. The design for a series of circular corrugated aperture feeds to meet these requirements is presented. The feeds are based on a circular waveguide OMT covering a full waveguide frequency band with interchangeable corrugated apertures to cover three sub-bands. In order to validate the design of this series of scalar feeds, high accuracy cross-polarization data was collected. The primary limiting factor in the measurement of the polarization ratio was the finite polarization ratio of the source antennas. A technique for correcting for the polarization ratio of the source is presented along with measured data on the feeds. The technique begins with the accurate characterization of the linear polarization ratio of the standard gain horns using a three antenna technique, followed by pattern measurements of the feeds, and ends with the removal of the polarization error due to the source antenna from the measured data. Measured data on these feeds is presented before and after data correction along with data predicted using the CHAMP® moment method software.

14' x 14' Portable Planar Near-Field Scanner System (PPNFSS) for the AEGIS Array

Authors: George E. Mc Adams, Richard Romanchuk

Publication: AMTA 1999

Copyright Owner: NSI-MI Technologies

This paper presents an accurate and portable method for RF testing of AN/SPY-1 Antenna Arrays on Navy ships. With four antennas per ship, the usual methods for RF testing are time consuming and very costly. Currently, the most thorough and accurate method of testing is to remove an array and ship it to the original equipment manufacturer's near-field facility. A Portable Planar Near-Field Scanner System (PPNFSS) was developed by Nearfield Systems Inc. for the Naval Surface Warfare Center-PHD to perform RF testing without removing the array from the ship. The system consists of a portable robotic scanner, optics, microwave subsystem, environmental/anechoic enclosure and active thermal control system. The system was designed to mount to various array/ship configurations with severe envelope and environment constraints. The design is modular to allow packaging in ruggedized transit cases and a 48 ft. shipping container.

A Technique to Evaluate the Impact of Flex Cable Phase Instability on mm-Wave Planar Near-field Measurement Accuracies

Author: Daniël Janse van Rensburg

Publication: ESA ESTEC Workshopon on Antenna Measurements

Publication: European Space Agency

The impact of flex cables on mmwave planar near-field measurements is considered. It is demonstrated how to estimate measurement errors due to these effects and an example is presented. The techniques shown here allows one to evaluate existing antenna test facilities to assess their suitability for mm-wave testing and also shows that flex cables provide very accurate results despite their imperfections.

View The Paper