Governments place restrictions on increasing RFID reader power to increase range. But conceptually and practically, if one increases a reader's power, does that mean an instant increase in range? If so, what are the limitations?
There are several factors that affect the read range of a passive ultrahigh-frequency (UHF) RFID system. These include the reader's transmission power, the reader antenna's gain, the tag antenna's size and design, the amount of cable loss (a long cable between a reader and an antenna will cause a loss of transmission energy) and environmental conditions, such as the presence of water.
If all conditions are equal, then increasing the reader's transmission power should increase the tag's read range. All readers, however, have a limit on how much power they can emit. Additionally, water absorbs RF energy in the UHF spectrum and the human body is mostly composed of water, so increasing the power output beyond the legal limit could be harmful to people.
—Mark Roberti, Founder and Editor, RFID Journal
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