US Patent No. 8,018,323, RFID sensor device based on pulse-processing
This technology is about a radio frequency identification device having sensing elements incorporated in the clock generators of its tags, which generate a leading code and an identification code. In the interrogator, the leading code is detected and its pulse width is measured for calculating sensing values and the baud rate in receiving the identification code. No analog to digital converter is needed in digitizing sensing values and only discrete signals exist in sensing signal generation and communication. The tag device is insensitive to variations in its power supply voltage obtained from a continuous wave RF carrier.
Uniqueness and benefits of this technology:
1. A mixed pulse sequence including discrete signals carrying analog sensing values and digital signals with ID information encoded is used for communication between sensing tags or sensing groups and an interrogator;
2. Sensing process is combined with communication process;
3. No analog signal exists in sensing tags and no ADC is required. Thereby sensing tags are insensitive to variations in supply voltage;
4. An independent oscillator is used in sensing tags.