Modelling Large Radio Telescope Visibilities Including Array Mutual Coupling Effects

Radio telescopes composed of phased arrays, called stations, produce visibilities by cross-correlating signals of beamformed antenna voltages from each station. For large telescopes with many stations, accurately modelling visibilities presents computational challenges due to the need for full-wave simulations of each antenna's electromagnetic response, including Mutual Coupling (MC) effects, and the evaluation of array patterns across many directions and frequencies. This paper leverages two in-house tools: the Fast Array Simulation Tool for rapid electromagnetic simulations and the OSKAR simulator for parallelized interferometric computations. For the first time, we analyze the impact of intra-station MC on the visibility time-delay impulse response across different station layouts, focusing on the 224 core stations of the Square Kilometre Array Low telescope. We show that MC significantly broadens the delay spread of instrument response, creating a key limitation for 21-cm science experiments while offering new insights into challenges posed by MC in large-scale radio telescopes.