OTA Testing of Antennas and Devices using Plane Wave Synthesizer

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Over-The-Air (OTA) testing aims to determine performance parameters of a device in the Far-Field (FF). The FF condition is achieved at sufficient distance between the device and the probe/range-antenna where the wave-front radiated by the device and probe/range-antenna approximates a plane- wave. For electrically large devices this condition may require a large separation and a corresponding high free-space attenuation. Alternative testing methods is to use a Plane Wave Generator or Synthesizer (PWG/PWS) as probe or range- antenna. The PWS approximates the desired plane-wave condition and thus FF condition over a finite volume at a reduced distance called the Quiet Zone (QZ). Examples of such generators are the Compact Antenna Test Range (CATR) and array based PWS. The latter consists of an array of elements with suitably optimized complex coefficients. In [1,2], the concept of a high performance, dual polarized PWS supporting up to 1:10 bandwidth was presented. A demonstrator of a dual polarized PWS has been designed, manufactured and tested in the 600MHz to 6GHz frequency range.

In this paper, we report on the measured QZ performance of different implementations of the PWS demonstrator. QZ fields are determined within a volume by spherical NF measurements and back-propagation. It is shown experimentally that the QZ field uniformity can be trade-off with size. Results of the verification testing and comparison to spherical near field measurements are reported using electrically small devices.

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