2019 · 10 citations · 8 references
EngineeringElectrical EngineeringAntennasMicrowave EngineeringWireless CommunicationsAntenna DirectivityAntenna MeasurementAntenna ParametersAntenna RadiationAntenna SimulationMicrowave MeasurementsAntenna Directivity MeasurementAntenna Far-field MeasurementFar-field MeasurementFar-field PropagationField MeasurementsFraunhofer DistanceMeasurementMillimeter-wave Propagation
OTA performance evaluation traditionally requires large anechoic facilities, yet recent work shows that direct far‑field measurements can be accurately performed at much shorter ranges than the Fraunhofer distance, a finding that is especially relevant as millimeter‑wave 5G technologies expand. This study aims to validate the feasibility of reduced‑range direct far‑field OTA measurements by introducing an innovative method that simulates spherical measurements for arbitrary DUTs, test probes, and range lengths. The authors employ this simulation approach and identify two key factors—finite probe resolution and the capture of only two E‑field components—that cause dependence on range length. The experiments confirm that the shortened range is relevant for measuring peak EIRP/EIS as well as total TRP/TIS, and demonstrate that the common assumption of range‑independence for TRP/TIS measurements is incorrect.
Over-the-air (OTA) performance evaluation requires large investments in anechoic environments. The question of minimizing the test distance is hence critical, and even more in this time where millimeter-wave technologies are about to be largely deployed in 5G devices. A recent publication has identified that direct far-field measurements can be accurately carried out at a much shorter range length than the well-known Fraunhofer distance. This paper introduces a further validation of this reduced distance, by employing an innovative method to simulate spherical measurements with arbitrary DUT, test probes and range lengths. The studies carried out confirm the relevance of this shorter distance, not only for the evaluation of the peak equivalent istropic radiated power (EIRP) or sensitivity (EIS), but also for the total radiated power (TRP) or sensitivity (TIS). In addition, it is demonstrated that the usual assumption that the TRP or TIS measurement is almost independent from the range length is flawed. Two main reasons relating to the test antenna are established which create this dependence: (i) OTA test probes have a finite resolution, and (ii) the probe and instrumentation typically captures the magnitude of two components of the E-field, which are not straightforwardly related to the power density in the near-field.
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