Patent ID: 10832544

Abstract:
A method of detecting a metal object in a detection zone between a transmitting antenna (101) and a receiving antenna (102) installed in proximity of a revolving door (110), the method comprising: in real time: demodulating a signal received via the receiving antenna (102) to provide a first signal (y; 501); filtering the first signal (y; 501) by a first adaptive notch filter (201) to suppress at least a fundamental tone or a fundamental tone and one or more harmonic tones of the fundamental tone in a filtered signal (e; 502); and processing the filtered signal (e; 502) to detect an impulse (504), and while the impulse develops, computing a feature value of the impulse and determining whether the feature value exceeds a threshold. In case the feature value exceeds the threshold, setting a first alarm detector. In this way a so-called booster bag can be reliably detected the moment it passes the detection zone.