This paper presents a prototype RFID humidity sensor capable of passive wireless sensing through far-field backscatter coupling. A commercial UHF RFID tag is employed as a sensing platform to receive the power and to reflect the sensed data back to the RFID reader. A humidity sensitive polyimide film is incorporated onto the top surface of the RFID tag for humidity sensing. The prototype sensor demonstrated that power required to activate the sensor tag is a linear function of relative humidity and the maximum sensing distance between the reader antenna and the RFID humidity sensor tag reaches to about 1.5 m. Due to its unique features of low cost, battery-less wireless operation, maintenances-free, and disposable, the RFID humidity sensor can be integrated into wallpaper for humidity monitoring in a built environment.

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The incorporation of dead zones in the error signal of basis function networks avoids the networks' overtraining and guarantees the convergence of the normalized least mean square (LMS) algorithm and related algorithms. A new so-called error-minimizing dead zone is presented providing the least a posteriori error out of the set of all convergence assuring dead zones. A general convergence proof is developed for LMS algorithms with dead zones, and the error-minimizing dead zone is derived from the resulting convergence condition. The performance is compared with the performance of classical dead zones.