A Method for Making Fast High Accuracy Polarization Measurements

Authors: G. Bruce Melson, Joseph J. Anderson

A method is presented for making fast multifrequency high accuracy polarization measurements using a digital computer. This paper will provide a brief review of the IEEE standard polarization definitions, their applicability to the three antenna method, and finally a fast two antenna method.

The fast two antenna method uses a dual polarized orthomode sampling antenna along with a standard antenna whose polarization is known. The dual polarized sampling antenna is calibrated before the test data is acquired using the polarization standard in two different orientations 90 degrees apart. Once the calibration data is acquired the dual polarized orthomode antenna is used as a sampling antenna for the AUT.

Since the sampling antenna is dual polarized the AUT polarization data can be obtained rapidly for many frequencies since neither antenna is required to rotate. This method has been used to acquire polarization data for over 500 frequencies in less than 20 seconds.

 

Prime Focus Feeds for the Compact Range

Author: John R. Jones

Prime focus fed paraboloidal reflector compact ranges are used to provide plane wave illumination indoors at small range lengths for antenna and radar cross-section measurements. The “quiet zone”, which is the region of space within which a uniform plane wave is created, has previously been limited to a small fraction of the reflector size. A typical quiet zone might be six feet by four feet for a ten foot radius reflector.

Two new feed antennas have been designed which can provide an increase in quiet zone size as defined by the amplitude taper in the quiet zone field. Design details for the feeds are presented and the performance of the feeds in a compact range is discussed.

 

Large Compact Range Quiet Zone Characteristcs

Author: James D. Huff
Publication: AMTA 1986
Copyright Owner: NSI-MI Technologies

Measurements of the Electromagnetic Field in the quiet zone of Scientific-Atlanta's Model 5753 Compact Range are presented. The Model 5753 is believed to be the largest high frequency compact range yet built and measurements demonstrate a quiet zone exceeding 8 ft. high by 12 ft. wide. Both field probe measurements and pattern comparison measurements are presented in the operating frequency range of 1-94 GHz.

 

Time Domain Gating in RCS Measurements

Author: J. L. Bradberry
Publication: AMTA 1986
Copyright Owner: NSI-MI Technologies

Gating is a widely used technique of improving RCS measurements. However, the exact type of gating used has a dramatic effect on such parameters as dynamic range and clutter rejection. Time Domain Gating offers significant advantages over software gating as used in some network and spectrum analyzers. This paper explores a technique used by Scientific-Atlanta in CW and FMCW RCS measurements. With the adaptation of an external computer controlled hardware gating unit, existing RCS and antenna systems can be retrofitted for significant performance improvements.

 

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