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60 Foot Anechoic Chamber

NSI-300V-30x15 planar nearfield scanner

NSI-300V-30x15 planar nearfield scanner

The 60 foot anechoic chamber is twenty feet square in cross section and has an overall length of sixty feet. All chamber surfaces are lined with pyramidal microwave absorber as illustrated in the figure below. The primary test instrument in this chamber is the Nearfield Systems, Inc. NSI-300V-30x15 planar nearfield scanner, which supports a 15-ft by 30-ft rectangular scan region. The 24-inch back wall absorber enables nearfield measurements that cover the frequency range from L-band through Ka-band. The system is controlled by a turnkey NSI system that includes a Panther© receiver to support high speed multiplexed data collection, including polarization switch capability. Physical dimensions of the scanner are available by clicking here.

The 60-ft chamber was originally configured as a short indoor farfield range, and the positioner and data collection system may be made available on special request. The illumination horns are mounted at the control room end of the 60 foot chamber providing for convenient and efficient change of these horns. A wide-band tunable, phase-locked loop amplitude and phase receiver is directly applicable over multiple bands; however, the receiver mixer (mounted near the antenna under test) must be changed from band to band. The positioner control and indicating equipment allows operator control of the elevation, azimuth and polarization of both illuminating horn and of the antenna under test. The farfield range is normally used at X-band and higher frequencies.


Illustration of the 60-ft chamber floor chart

Mesa 60-ft Chamber -- Plan View

MSL Cruise Stage Mockup mounted in the 60-ft anechoic chamber.

MSL Cruise Stage Mockup mounted in the 60-ft anechoic chamber.

The far-field range positioner in the 60-ft chamber has also been used to perform spherical nearfield testing by collecting a spherical grid of data around the AUT. Software developed at JPL was used to transform the nearfield grid into farfield antenna patterns. This technique permits one to measure antennas and structures whose farfield region is much larger than the 50-ft distance supported by direct measurements in this chamber. The maximum AUT size for spherical measurements is limited by the distance to the nearest wall in the range and the size of the chamber access door along with data collection and processing time. As an example, the 15-ft diameter Mars Science Laboratory (MSL) Cruise Stage mockup was measured in the chamber using the spherical near-field method. Note that this is not a standard, supported measurement -- consult with MESA staff for additional information regarding this capability.

The azimuth positioner in the 60-ft chamber is track mounted in a pit below the floor of the chamber. The pit extends the length of the chamber and is covered by a heavy duty wooden structure which provides a continuous floor. The upper surface or mounting plane of the positioner is nearly flush with the chamber floor. This permits easy removal of the existing traverse table assembly and installation of other test antenna support structures when required. Since the pit extends to the AUT mounting region of the 15x30 scanner, steel beams are sometimes used to straddle the pit for high frequency measurements.

The azimuth positioner in the 60-ft chamber
Azimuth positioner in the 60-ft chamber

Although this chamber is located below ground level, rear wall access doors are provided for access to the chamber through a ground level anteroom equipped with a 1-ton crane for moving the antenna under test into the chamber. The anteroom also provides a climate controlled space for hardware assembly.







Location: Mesa Facilities Map