Wireless moisture sensor using a microstrip antenna

A wireless moisture sensor has been developed on the basis of the backscatter characteristic of the microstrip antenna,which works in the far field without a battery. this study aims to develop a wireless sensor with a long communication distance and to apply the wireless applications,such as monitoring the moisture in the wrapped products and surface adsorption of hydrogen peroxide in the biological isolation systems. the dropwise addition of the distilled water on the cleaning tissue is clearly detected by the measurement of the backscattered power from the sensor at the frequencies of 0.954ghz and 2.45ghz. the ratio of the backscattered power in two frequency bands can be used as an index to measure moisture. copyright © 2011 tatsuo toba and akio kitagawa.