  Characteristic Modes Analysis (CMA) is a widely used method with recent
progress in multi-antenna systems. We employ this method to characterize the
mutual coupling phenomenon between two SKALA4.1 antennas, the low-frequency
array elements of the future radiotelescope Square Kilometer Array (SKA-Low).
The CMA accuracy is first validated at the lowest frequency range of interest
with respect to a standard Method of Moments (MoM) solution by decomposing the
single antenna into its characteristic modes. We then examine critical
frequencies of a two-antenna system in modal decomposition, and characterize
those responsible for the radiated electric field spurious spectral features
owing to the mutual coupling. We connect these modes to first-order coupling of
single antenna CMA modes, by using the eigenvalue data of both single- and two-
antenna simulations.
