Wireless humidity monitoring in hermetic biomedical micropackages

A miniature moisture sensing system is developed for wireless humidity monitoring of implantable micropackages. This 1/spl times/1.5/spl times/6.5 mm/sup 3/ system consists of a capacitive humidity sensor and a hybrid coil, enabling one to monitor humidity inside a small package using telemetry, using a single-turn antenna from a distance of up to 1.5 cm from the sensor. The resonance frequency of the coil and capacitor circuit shifts 8 kHz per %change in relative humidity (RH) within a 5% RH resolution.