Methods, systems and computer program products are provided estimating a physiological characteristic of a subject based on a reflected signal received by a UWB radar system. The method comprises: processing a signal received from the UWB radar system to obtain a frequency domain representation of the signal； discerning, from the frequency domain representation, a plurality of elements considered to belong to a physiological characteristic harmonic set {PC0, PC1, PC2, PC3 . . . }, the physiological characteristic harmonic set comprising a fundamental frequency of the physiological characteristics and harmonic frequencies of the physiological characteristic； and estimating the physiological characteristic based on the discerned elements of the physiological characteristic harmonic set.
