Short-Time Measurement and Transformation of Continuously Modulated Time-Harmonic Fields

Near-field antenna measurements together with corresponding near-field to far-field transformations are commonly performed with time-harmonic fields. In in-situ measurement scenarios, where the antenna under test (AUT) cannot be accessed to transmit or receive a specifically tailored test signal, it is desirable to perform required measurement tasks with the signals transmitted by the AUT under standard operational conditions. If such measurements are performed by an unmanned aerial vehicle (UAV) carrying the probe, the UAV movement is detrimental for long measurement times at fixed measurement positions in order to resolve the spectral distribution of modulated signals. It is, therefore, necessary to retrieve all the required signal information from measurements with short observation or integration times. In this contribution, we present measurements that demonstrate the applicability of this short-time measurement approach for the measurement and near-field to far-field transformation of narrow-band periodic and continuously time/space-modulated fields.