This invention provides a method and
system for inventorying
wireless transponders, specifically referred to as RFID
transceiver devices. The RFID
transceiver devices are certifiable by a recognized standards body, such as EPCglobal, or are compatible with recognized standards but have higher functionality than typical passive RFIDs, and yet are implemented with techniques that lower cost and battery requirements.
Backscatter techniques of standard passive RFIDs are used to keep cost and battery requirements low. To provide higher functionality, a
microcontroller is used in the RFID, along with a battery, but the
clock frequency of the
microcontroller is adjusted, based on external input, to minimize battery requirements. In one embodiment, the
microcontroller initially has a zero or near zero
clock frequency. A
comparator compares the received RF energy to a threshold, and when the threshold is exceeded, indicating the presence of a
probe signal from an RFID reader, the microcontroller
clock frequency is immediately increased, and further adjusted based on the received data. In an alternate embodiment, the clock frequency of the microcontroller is adjusted based on data from sensors, to keep the clock speed at the proper speed to adequately process the data while minimizing the power requirement of the microcontroller, and then create an input to modulate the backscattered
signal to be transmitted by the RFID. The received data can also cause the microcontroller to request the sensors to generate
sensing data at a faster rate, which in turn requires the microcontroller clock to increase to
handle the increased sensor data. In an additional embodiment, multiple sensors are multiplexed to provide a single input
stream to the microcontroller, reducing the microcontroller clock speed required, along with the overall cost of the microcontroller and sensors.