passive tags wait for a RF signal from an RFID reader, RFID reader sends power energy via antenna which converts the energy into an RF wave enough to power on power off RFID passive tag.Once Passive tag is received wave/power within the read covering zone, the RFID tag's internal antenna draws in energy from the RF waves to make transaction btw reader and passive tag.

Generally speaking, three main parts make up in a passive RFID system – an RFID reader or interrogator, an RFID antenna, and RFID tags. Unlike active RFID tags, passive RFID tags only have two main components – the tag’s antenna and the microchip or integrated circuit (IC).

As the name implies, passive tags wait for a signal from an RFID reader. The reader sends energy to an antenna which converts that energy into an RF wave that is sent into the read zone. Once the tag is read within the read zone, the RFID tag’s internal antenna draws in energy from the RF waves. The energy moves from the tag’s antenna to the IC and powers the chip which generates a signal back to the RF system. This is called backscatter. The backscatter, or change in the electromagnetic or RF wave, is detected by the reader (via the antenna), which interprets the information.

As mentioned above, passive RFID tags have no internal power source, and a standard passive RFID tag consists only of an IC and internal antenna; this basic structure is commonly referred to as an RFID inlay. Countless other types of passive RFID tags exist on the market, but all tags generally fall into two categories – inlays or hard tags. Hard RFID tags are durable and made of plastic, metal, ceramic and even rubber. They come in all shapes and sizes and are typically designed for a unique function, material, or application.

A few different groups work to further divide passive hard tags; however, some tags will exist within two or more groups.