T.Ya. Shevgunov1

1 Moscow Aviation Institute (National Research University) (Moscow, Russia)

1 shevgunov@gmail.com

Problem statement. Contactless detection of human vital signs is a relevant area of research that forms a scientific basis for solving the problem of reliable human detection and preliminary assessment of their physical condition. Timely detection of people who have remained motionless for a long time is critical in cases where it is necessary to make decisions on whether to carry out active rescue operations or not in cases where there is a possibility that after natural or man-made disasters living people, motionless or fixed by external objects, remain blocked in cavities formed from collapsed and damaged panels used in the construction of buildings and structures. The conducted analysis of human vital signs showed that the signal generated by the breathing process, during which quasi-periodic movements of the chest wall occur due to rhythmic changes in lung volume, has the greatest power. It was shown that such a process in the received radar response manifests itself as a random signal, the properties of which can be described by the model of a cyclostationary random process. This representation is a prerequisite for developing an algorithm for identifying a breathing signal in a secondary radar signal based on identifying characteristic cyclic frequencies in estimates of spectral correlation functions.

Goal the aim of the work is to develop an algorithm for detecting signs of vital activity of a stationary person in the form of an algorithm for digital processing of secondary radar signals based on estimating the parameters of cyclostationary models of breathing signal representation.

Results. The article presents a block diagram of the developed algorithm for processing secondary radar signals to identify characteristic cyclic frequencies specific to breathing signals of a stationary person. The main procedure of the algorithm consists in sequential processing of signals contained in the range lines of the radar frame, and includes preliminary processing to remove low-frequency offset and high-frequency noise, forming an estimate of the spectral correlation function and calculating pseudopower based on it, selecting cyclic frequencies exceeding a variable threshold. The operation of the algorithm is demonstrated on experimental data obtained using a radar system emitting signals with step frequency modulation.

Practical significance. The proposed algorithm for detecting signs of human breathing in secondary signals processed by a radar system can be used in developing new and upgrading existing technical solutions, such as contactless health and safety monitoring systems for objects, highly specialized solutions designed to detect survivors in rubble or to help people with disabilities.

The study was supported by state assignment of the Ministry of Education and Science of the Russian Federation, research projects No. FSFF-2023-0005

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