A radar system for indoor human localization and breath monitoring

This paper presents the study of a radar system for indoor human localization and vital signs monitoring. The article illustrates different solutions including linear frequency-modulated continuous-wave (FMCW) mode and recently proposed hybrid schemes, combining FMCW and continuous-wave (CW) interferometry modes. A new operating modality based on the use of the phase variations of the demodulated FMCW signal is also proposed. The presented schemes have been investigated theoretically and simulations have been performed to analyse and compare different algorithms needed to extract distance and breathing information. A radar system working in the 24 GHz ISM band with a bandwidth of 250 MHz has been realised. The sensor is based on the Infineon BGT24MTR11 integrated circuit. As transmitting and receiving antennas an appropriately designed serial array of patch antennas and commercial horns have been used. A series of experiments to evaluate the ability of the radar to estimate both the position of a target and its small displacements have been carried out. Maximum registered errors are about 6 cm in range measurement and 30 μm in small movements. All the obtained results are in good agreement with simulations performed with a Matlab TM code reproducing the experimental scenario.