A validated reactive near-field phasor measurement system for antenna pattern measurements

Abstract

Correlation of close near-field measurements with radiated field patterns will mitigate test efforts for electromagnetic compatibility (EMC) testing and antenna characterization. A novel automated reactive near-field testbed based on photonic phasor probes is presented. The scanning system combines a large scanning volume with micrometer resolution. An optical surface reconstruction system allows the structure of the device under test (DUT) to be measured with better than 20 µm uncertainty, allowing scans at a precisely known distance above arbitrary electronic components. Miniaturized active microphotonic electric and magnetic field probes for the 0.01 – 6 GHz frequency range, combined with a high-speed vector signal analyzer, are applied to measure the electromagnetic (EM) phasor-field distribution with a dynamic range of >120 dB. The fully isolated probes eliminate perturbations of the EM fields generated by the DUT compared to electrically connected near-field probes and offer up to 60 dB better sensitivity than passive electro-optical probes. The testbed allows high-precision broadband near-field 3D scans for antenna characterisation to be performed with excellent inter-laboratory repeatability. The phasor measurement capability enables near-to-far-field transformation and thus direct correlation of nearfield and radiated characteristics.