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RFID Basics: Antenna Gain and Range

Posted: 16 Oct 2007     Print Version  Bookmark and Share

Keywords:antenna gain  read range  tag antenna 

This article, which is part of the book providing the basics on RF and RFID, discusses antenna gain and range. In the most general case, the power received at the reader goes as the inverse fourth power of the (symmetric) distance. It is also proportional to the square of the antenna gains, so when reverse link power is important (e.g. when a semipassive tag, or an unpowered device like a surface-acoustic-wave (SAW) tag, is used) the antenna gain plays a very large role in achievable read range. Real tag antennas have some gain, but it is typically modest (around 2 dBi, since they are usually dipole-like), and since we don't always control the exact orientation of the tag antenna and may not be able to guarantee that the main beam of the tag antenna is pointed at the reader, it is prudent to count on minimal gain from the tag antenna.

View the PDF document for more information.





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