Disclosed is a method for determining a type of an object arranged in a radio frequency, RF, field transmitted by an NFC reader device. This method involves analyzing the oscillatory behavior in the NFC reader device, after the RF field transmitted by the reader has been switched off, using a decomposition scheme with a degree M for decomposing a decay signal trace into M superimposed components. The method involves predetermining the decomposition scheme with a degree M for decomposing a decay signal trace into M superimposed components, e.g. weighted oscillation components, wherein each one of said M superimposed components is defined by a predetermined superimposition function, which in turn is determined by an associated set of characteristic parameters, and storing, e.g. in a database that is accessible for the P&E unit, an indication of the decomposition scheme and the M predetermined superimposition functions.