How Can I Calculate Power With Respect to RSSI and Tag Sensitivity?

By RFID Journal

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Ask The ExpertsHow Can I Calculate Power With Respect to RSSI and Tag Sensitivity?
RFID Journal Staff asked 6 years ago

What is the received signal strength indicator, how is it used and how can I measure it? And what is meant by tag sensitivity?

—RK

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RK,

The received signal strength indicator (RSSI) is the amount of RF energy being received from a tag, and is used to estimate that tag’s distance from a reader antenna. There is no standardized method of measuring this, to my knowledge, as different reader manufacturers use different methods of calculating the RSSI. If any of our members have more information about calculating RSSI, they are invited to post information below.

Tag sensitivity relates to a tag’s ability to harvest energy from a reader and reflect back a signal strong enough for the reader antenna to pick up. If a tag harvests energy and reflects it back more efficiently, it can be read from farther away or through materials better, so it is said to be more sensitive.

CISC Semiconductor and Voyantic make test equipment that enables a user to energize a tag and evaluate its response. You can test a variety of tags in free air and compare the read range, or test the same tag on different surfaces or products to determine how read range is affected by the material on which the tag is placed.

—Mark Roberti, Founder and Editor, RFID Journal

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