A medical analysis system, includes at least one catheter to be inserted into a body-part having a tissue surface, and comprising sensing electrodes to contact and receive electrical signals from the tissue surface, and processing circuitry to receive unipolar signals from individual ones of the plurality of the sensing electrodes, compute a combined far-field and mid-field signal based on summing and filtering ones of the received unipolar signals received from at least a pair of sensing electrodes disposed around a point of interest, compute a far-field signal as a weighted average of the received unipolar signals, weighted according to respective distances of the sensing electrodes from the point of interest, and compute and output a mid-field signal, representative of electrical activity below the tissue surface at the point of interest, based on subtracting the computed far-field signal from the computed combined far-field and mid-field signal.
