INTRODUCTION
WIRELESS operation of sensors is desirable in many
emerging applications where they must operate in
harsh environments and physical access to them is impossible.
An LC type passive wireless sensor is one of the approaches
to remotely monitoring the parameters of interest, where the
sensing system is powered remotely and occupies a small
volume. The humidity measurement [1]–[5] and temperature
measurement [6], [7] have been studied by using the LC type
passive wireless sensor. The sensing principle is usually based
on changes of the capacitance which represent a variation on
the resonant frequency of the sensor tank. In fact, however,
parameters of interest to be monitored often include both
humidity and temperature [8], [9]. Hence, simultaneous remote
sensing of both temperature and humidity by the LC-type
passive wireless sensors is greatly desired [10], [11].
On the other hand, environmental temperature is even used