Strong Mutual Coupling Effects on LOFAR: Modeling and <italic>In Situ</italic> Validation

Abstract

Front-end amplifiers with high input impedance are exploited to build active array elements for modern low-frequency radio telescopes. The combination of such loading and mutual coupling between adjacent elements is responsible for the deep nulls that are present in some embedded element patterns (EEPs) of the Low-Frequency Array. This paper quantifies this phenomenon with both models and experimental data. The full-wave array simulations and the measured amplifier scattering parameters are combined to obtain the EEP models. These models are in good agreement with the in situ measurements that have been performed with a micro unmanned aerial vehicle carrying a field source.