The present disclosure teaches a calibration system, a calibration apparatus and a method for calibrating a signal path and a method for calibrating a delay. The calibration system comprises an injector, a calibration signal generator, a correlator, a detector unit, a polygon former and a pattern classifier unit. The calibration system is adapted to calculate a fraction of a delay from a set of polygons. The delay is being accumulated along a signal path. The fraction of the delay is indicative of an accuracy of the delay at a fine sampling rate as if the delay was measured at the fine sampling rate being an integer multiple of the coarse sampling rate. The method for calibrating of the signal path uses a calibration signal sampled at a coarse sampling rate. Correlation techniques are used in order to detect a fraction of the delay from a set of polygons.