A feasibility study on simultaneous data collection from multiple sensor RF tags with multiple subcarriers

Wireless and battery-less health monitoring of machinery and structures have been a dream in mechanical engi-neering. Particularly, simultaneous data collection from multiple sensors is required to detect failure or malfunction before it becomes fatal problem. In this paper, a concept of simultaneous data collection from multiple sensor RF tags with multiple subcarriers is proposed and its feasibility is examined. To facilitate the inclusion of sensor data in RF tag and to obtain the number of available communication channels, an analog modulation of digitally generated subcarriers is employed. The unavoidable mutual interference among subcarriers, stemming from the pulse shape of subcarrier in RF tags, is eliminated by a swift interference rejection method. We examined the feasibility and the performance of the concept with a two-subcarrier prototype in which the interference rejection is executed in a software defined radio platform. It is shown that the proposed concept is feasible. In order to evaluate the effect of the interference rejection method, we examined the correlation between the original sensor data and the recovered sensor data in a worst case interference environment. It is shown that the correlation coefficient is significantly improved from 0.00 to 0.91.