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Publication Date: 2016-Nov-18
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The Prior Art Database

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Over-the-air (OTA) testing is generally desired to evaluate various performance parameters of a communication system, such as a wireless communication system that uses a multiple-input-multiple-output (MIMO) antenna array or a radar system that uses a phase antenna array.  A few examples of OTA testing include: 1) antenna array test and calibration, 2) per channel radio-frequency (RF) parametric tests such as error vector magnitude, adjacent channel power ratio, and spurious emission, 3) beamforming performance tests such as to determine radiation pattern, directivity, and total radiated power, and 4) receiver sensitivity measurement.  Some of these OTA tests can have conflicting requirements that define the nature of the test set-up.  For example, a far-field antenna test set-up for testing some types of antennas can be distinctly different than a near-field antenna test set-up for testing some other types of antennas. 

As is known, OTA tests are typically carried out in an anechoic chamber having dimensions that are proportional to the size of the antenna being tested.  Thus, when the OTA testing involves a near-field test of an antenna, the dimensions of the anechoic chamber can be relatively small in comparison to the very large dimensions that would be needed for carrying out a far-field test of another antenna.  This problem can be mitigated to some extent in some cases by carrying out a near-field test set-up and converting the near-field test results into far-field test results.  However, there are several shortcomings in taking this approach.  For example, one type of near-field test that uses a compact antenna test range (CATR) involves the use of a reflector element or lens to create a planar wave front representing a far-field condition.  Not only is the reflector element complex to design and fabricate, some tests such as those pertaining to adjacent channel leakage ratio (ACLR) and narrow-band blocking can turn out to be quite challenging.  Furthermore, some near-field test measurements, such as equivalent isotropic sensitivity (EIS) and radiated error vector magnitude (EVM), can turn out to be difficult to convert to equivalent far-field results. Thus, traditionally, two different test fixtures have been used - one for conducting near-field tests and another for far-field tests.  The two different test fixtures approach can be quite expensive in terms of hardware costs (two anechoic chambers, duplicate test equipment, etc.), as well as in terms of testing time and effort.  

Consequently, what is proposed in this paper is a dual-purpose anechoic chamber that can be flexibly configured for carrying out either near-field tests or far-field tests as desired.  As shown below in Figs. 1 and 2, the dual-purpose anechoic chamber incorporates two anechoic blocking boards that can be flexibly used when carrying out one of a near-field test or a far-field test.  Fig. 1 shows anechoic blockin...