RFID systems are mainly used to identify objects or to track their location without providing any indication about the physical condition of the object. This technology uses electromagnetic or electrostatic coupling in the radio frequency (RF) portion of the electromagnetic spectrum to uniquely identify an object, animal, or person or an item with the help of RFID Chip.
Active sensor-tags use batteries to power their communication circuitry, sensors and micro-controllers. Thus, they have a rather long range (approximately 30 m) and they are able to achieve high data and sensor activity rates.
A passive sensor-tag with incorporated temperature and photo sensors that can be used for environmental monitoring . The proposed sensor tag is powered by an external ISM band RF signal and it senses ambient temperature and light. Zhou et al.  have proposed a passive UHF RFID tag RF front end with magnetic sensor. Their system includes a 900 MHz RFID front-end circuit and a mirror based magnetic sensor in standard CMOS process. Among its main advantages, one can point its high sensitivity and its low-power consumption. The proposed tag has a range longer than 10 m, operates at 2.45 GHz and 915 MHz.
An integrated passive and battery-powered semi-passive UHF RFID tag which supports the EPC Gen 2 protocol. The proposed sensor-tag functions as a passive RFID tag, when the generated RF power is sufficient to operate.