A system for measuring a peak frequency of a signal applies a Maximum Entropy Method to the signal obtained through transmission and reception of an electromagnetic wave to a subject to obtain a frequency of a peak component to be measured so as to acquire a predetermined information, avoiding influence of a noise, thus permitting to make an appropriate assessment on a state of the subject. A signal analysis unit (12) performs a spectrum estimation utilizing the Maximum Entropy Method applied to a signal part of the phase difference signal with a predetermined short analysis duration, from a phase difference signal obtained by an electromagnetic wave transmitting and receiving unit (11) and including also the noise excluding the peak component to be measured, to obtain a frequency indicative of occurrence frequency of the peak component, and conducts repeatedly the same process, while shifting a position to be analyzed, corresponding to the analysis duration, thus introducing continuously the frequency. It is therefore possible to know a transition with time of the frequency of the peak component and derive a state of variation of the peak component to be measured in the phase difference signal in a short period of time, so as to make an appropriate assessment.
PEAK FREQUENCY MEASUREMENT SYSTEM FOR SUBJECT-STATE ANALYZING SIGNAL