Automated EIRP Measurements On A Near-Field Range

Authors: Gregory F. Masters, Ron Young
Publication: AMTA 1996
Copyright Owner: NSI-MI Technologies

Accurate EIRP measurements are possible to make on a near-field range but require great care and attention to detail. NSI has recently implemented a near-field test range for the Globalstar satellite program which makes automated EIRP and gain measurements. Automation for this program is extremely important since the production cycle requires testing many antenna systems per month, each of which has two antennas with 16 separate beams per antenna. Among the various range measurements, EIRP is the key parameter of the Transmit antenna’s performance. This paper reviews the measurement theory of EIRP measurements and presents some of the results of this automated activity.

 

Cross-Polarization Measurement Accuracy Improvement on a Single Reflector Compact Range

Author: David C. Cook
Publication: AMTA 1996
Copyright Owner: NSI-MI Technologies

Scientific-Atlanta has developed a new algorithm for obtaining high accuracy cross-polarization measurements from prime focus, single reflector, compact ranges. The algorithm reduces cross-polarization extraneous signals to levels that rival or exceed much more expensive dual reflector systems, but with the associated cost and simplicity of a single reflector system. This paper provides an overview of the new algorithm. It explains the limitations on conventional polarization measurements in single reflector systems and the methods for overcoming these limitations without error correction for some antennas. A method for determining if error correction is needed for a particular antenna is reviewed and the fundamentals of the error correction algorithm are explained. Preliminary test results are provided.

 

Globalstar Satellite Near-Field Measurement Systems

Author: Greg Hindman
Publication: AMTA 1996
Copyright Owner: NSI-MI Technologies

NSI recently completed installation of two large 7m x 7m horizontal planar scanners to support the Globalstar satellite program test activity. These systems were installed at Alcatel in France, and Alenia in Italy. These two systems are similar to the NSI system installed at Space Systems/Loral in Palo Alto, CA. described in previous AMTA papers. The companies are part of the Globalstar satellite consortium, committed to launching a constellation of satellites for mobile telephone communications. The paper will summarize the hardware configuration and the unique features of the two new test systems including high power phased array testing and the interface to the Globalstar payload for active antenna control and payload testing. In addition, range data comparing all 3 test ranges will be shown.

 

HSC’s New Near-Field Measurement Facility

Author: Jeff Way
Publication: AMTA 1996
Copyright Owner: NSI-MI Technologies

construction, installation and validation of two large horizontal near-field antenna measurement ranges. These new measurement systems are located in the existing HSC satellite factory building. These ranges will be used to measure various types of directive satellite antennas both at a unit level and at spacecraft level. The facility will accommodate mechanical integration of the test articles as well. This facility is the result of Hughes committing the time and money to create a state of the art antenna measurement facility that will be highly efficient and accurate. A detailed description of this facility's configuration, design and current status will be discussed herein.

 

Compact Range Testing of High Power Antennas

Authors: Bridges Smith, Virginia Jory, David Cook
Publication: AMTA 1996
Copyright Owner: NSI-MI Technologies

Use of a compact range for testing high power antennas is generally limited to testing the antennas at low power levels. In most cases, this is adequate, but for antennas where the management and dissipation of power is a key test parameter, the antenna and transmitter must be tested at the design power level. If this testing is to be performed in a compact range, it is important that the energy be captured and safely dissipated because allowing the energy to be incident on the absorber could result in destruction of the facility. The chamber under construction for Hollandse Signaalapparaten in Hengelo, Netherlands is designed to receive this energy in a specific region of air cooled absorber and to dissipate the heat into the chamber as an added load on the HV AC system.

 

Practical Issues in Advanced Antenna Pattern Comparison

Author: Celestino A. Corral
Publication: AMTA 1996
Copyright Owner: NSI-MI Technologies

This paper addresses some of the practical considerations and numerical consequences of vsing the Advanced Antenna Pattern Comparison (AAPC) method to improve the accuracy of antenna measurements in compact ranges. Two main issues an of particular importance:

      Appropriateness of circle-fitting algorithm results to the measured data.
      Ambiguous circles due to the distribution of data.

These issues deal specifically with Kasa's circle-fitting procedure-an essential part of the AAPC method and provides useful checks for conditions commonly met with the use of this technique. We also briefly address the single interfering wave case that the AAPC method tacitly assumes.

 

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