Transponder antennas take the energy from the radio waves and transmit it to the RFID chip to switch it on. In general, the larger the antenna, the more energy can be collected and made available to the chip, increasing the read range. Current chips typically manage with less energy. Whether certain objects can be detected with RFID technology is therefore always a question of energy.
RFID reader and RFID antennas work as one system to read RFID transponders. RFID antennas convert electric current into electromagnetic waves, which are then radiated into space where they are received by a transponder antenna and converted back into electric current. Just like transponder antennas, there are a variety of RFID antennas. The optimal antenna varies depending on the specific application.
The two most common antenna types are linear and circular polarised antennas. Linear polarised antennas offer long ranges and radiate with high power. These allow different materials to be penetrated. Linearly polarised antennas are sensitive to the antenna orientation of the transponder. The wrong position of an object can lead to it not being read correctly. Conversely, circularly polarised antennas have circular fields. These are less sensitive to transponder alignment, but are not able to radiate as much power as linear polarised antennas.