2.4 GHZ FULLY INTEGRATED WIRELESS TEMPERATURE SENSOR WITH ON-CHIP ANTENNA

The on-chip antenna concept is the actual trend in integrated wireless sensor systems because it is a practical solution to compact, small size and low cost devices for short range wireless applications, like RFID tags and biomedical sensor data transmitters and other related applications. Rapid scaling of low cost CMOS technology has enabled circuits and systems to operate into the micro/millimeter wave frequency band, where the required antenna size shrinks and makes the implementation of an on-chip antenna feasible. An on-chip antenna (OCA) represents a possible solution for a fully integrated wireless system with no off-chip components, paving the way to new unexplored applications, such as miniaturized sensors for biomedical applications. In this paper an improvement of a wireless temperature sensor with on-chip antenna is proposed. This new solution uses the same principle, based however on a double ring oscillator structure, transforming the silicon substrate temperature variation into a frequency modulation. The design is realized by means of 0.35 mu m CMOS technology. This new chip works at about 2.4 GHz frequency (instead of 750 MHz of the oldest), improving the antenna efficiency. The signal is transmitted by a small loop antenna structure which is realized by aluminium deposition on the top surface of the chip.