Development of an Antenna Sensor for Occupant Detection in Passenger Transportation

We investigate a novel sensor system for occupancy detection in automobiles or mass transportation. The sensor system is developed on the basis of electromagnetic coupling between a transmitter and a receiver patch antenna. Based on the relation of the transmitted and received electromagnetic wave the occupancy of a seat can be reliable detected with minimum transmitting power. The antenna sensor is analyzed by applying finite element method (FEM) simulation for which different antenna performance parameters, e.g. S-parameter, Z-parameter, gain and directivity have been extracted and furthermore verified by measurements. It is shown that at 868 MHz with a relatively low radiated power level of 3dBm to 6dBm (2mW to 4mW), a reasonable and reliable occupancy detection could be achieved. A stand-alone sensor application including the evaluation hardware for signal processing has been manufactured to verify simulation data.