Spherical Near Field Range
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Test Facilities
  Near Field Range
  Spherical NF Range
  Far Field Range
  Antenna Chamber
  Turntable Range
   
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The Spherical Near Field Range at GTRI is a recently acquired antenna measurement facility supported primarily by Nearfield Systems, Inc. (NSI) positioners and software.

The positioning system is an ‘L’ bracket, roll-over-azimuth style, large enough for antennas that would fit within a horizontal cylinder 12 ft. long by 8 ft. in diameter.  The rotary stages are the largest offered by NSI with a 10,000 lb. vertical load capacity and a 2,500 lb. bending moment.  The frequency of operation is limited by absorber at the low end to 1120 MHz, while the high end is yet to be determined.  System validations on standard gain horns have been performed through Ku-band (12-18 GHz).

The chamber is covered in 12" and 24" pyramidal absorber, with several roll-around panels for measurement-specific placement requirements.
 

The spherical near field scanner has a phi/theta coordinate system or can be converted to Az/El coordinates.   The scanner is also capable of commercial near-field/far-field and holographic processing.  Our software includes a 3-D viewer for inspection of near field or far field data, which allows for interactive rotation and zooming of all data.

3-dimensional display of x-band standard gain horn pattern.


 
Standard gain horn being measured on spherical near field range.
Both local and automatic control is available for engineering/development requirements or for extensive programmed  measurements. The probe polarization rotator on the scanner may be controlled manually or automatically during measurements. An auxiliary computer is available for processing prior measurements during current data acquisitions.

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