Mathematical Simulation of Remote Detection of Human Breathing and Heartbeat by Multifrequency Radar on the Background of Local Objects Reflections Alexander S. Bugaev, Institute of Radioengineering and Electronics RAS, Moscow Valeri V. Chapursky, Sergey I. Ivashov, Bauman Moscow State Technical University Key Words: multifrequency radars, human detection, background reflections, mathematical simulation. SUMMARY The mathematical description of signal processing basic stages in multifrequency radar intended for detection of human breathing and heartbeat is given. Cross-correlation functions of different kinds of the multifrequency probing signals, modelling optimum processing of impulses are compared in view of resolution, levels of lateral lobes and presence of diffractive maxima. The model of multifrequency radar signal taking into account breath and palpitation of the person is offered. For remote allocation of person’s breath and heartbeat realizations with selection on range cells the spectral analysis in each range element is used. Such a selection besides definition of range up to the living human allows excluding reflections from motionless and inactive local objects, available in other range cells. 1. INTRODUCTION There is now keen interest to use of microwave radar methods for detection and diagnostics of human beings. The microwave signals reflected from individuals contain biometric information which is related to the periodical reductions of a heart, blood vessels, lungs and other human internals and fluctuations of the skin in the process of breathing and heart beating. These processes are cyclical and the frequency of their recurrence is in the range of 0.8 - 2.5 Hz for heart beating and 0.2 – 0.5 Hz for breathing. A reflected microwave signal containing biometric information we call as biometric radar signal. The main applications of this method could be: - detection of alive people who are buried under the building debris as a result of natural disasters, technical calamities or accidents; - detection of the people and parameters of their movements inside the building in process of law enforcement and antiterrorist operations; - remote testing of psychological conditions of the persons during the latent or open security checks, for example at the airports (remote lie detector); - touchless measurement of the heartbeat and breathing of patients, when a contact sensor for some reasons cannot be used. The useful components of biometric information are preserved in the time domain realization of the radar biometric signal. That realization is nonstationary in general case. Examination of its nonstationarity is needed especially in the case of person psychological condition testing and in medicine. Signal spectrums in frequency domain may be useful in process of alive human detection on the background of local objects reflections and other interferences. The theoretical spectrum estimation of a reflected biometric radar signal on the output of receiver devices of the microwave radar sensor with continuous sine-wave sounding was executed in [1]. The radar with non modulated signal does not allow determining distance up to the person, and also has no selection on range and as a consequence it is subjected to reflections and interferences from whole distance interval. One of possible construction of radar for detection of alive persons with selection on range is application of a wideband or ultra wideband (UWB) multifrequency probing signal. In achieving the range resolution comparable to that of UWB pulse signals, multifrequency signals allow receiving considerably greater average radiation power and detection range. The primary goal of the given research is mathematical simulating of remote allocation of breath and heartbeat realizations of the person by radar with selection on range cells. Such a selection besides definition of range up to the living person allows excluding reflections from motionless and inactive local objects, available in other range cells. Final stage of radar signal processing must reproduce the time realization of biometric signal. It is supposed, that the model will be useful in studying the opportunity and algorithms of division of breath and heartbeat realizations at subsequent processing a biometric radar signal. Such a division gives the precondition for more reliable allocation of information attributes of person’s psychological conditions in stressful situations. 2. DESCRIPTION OF MULTIFREQUENCY SOUNDING SIGNALS We suppose that the radar transmits impulse signal periodically with constant period r T and multifrequency 0-7803-8882-8/05/$20.00 (C) 2005 IEEE