RFID Reading patterns and how they are affected by users
IN THIS EXPERT ARTICLE WE DISCUSS RFID READING PATTERN BETWEEN DIFFERENT UHF RFID ANTENNAS AND THE USER’S IMPACT.
Different antennas have different RFID reading patterns, and objects affect the patterns. We will have a look at three different antenna designs and how their reading patterns are affected by the user.
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A directive UHF RFID antenna with circular polarization
The Nordic ID Sampo has a directive antenna with circular polarization which is less sensitive to tag orientation than other antennas. The nominal reading range is 6m with full power.
The user operating the unit blocks the RF signal from the reader casting a “shadow” in the reading range. (This has to do with the fact that the human body contains water, which attenuates the RF signal). Tags behind the user are harder to read. The reading range can also be controlled with programming to be narrowed down but the human impact will still stay about the same. The benefit in this case is that e.g. in point-of-sales use, the reader will not read any other items than the ones placed on the defined reading area.
Picture 1. The reading pattern from the side and from above and how a human being affects it.
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An omnidirectional UHF RFID antenna
In a certain plane an omnidirectional antenna’s reading pattern radiates power equally in every direction. For instance, if the antenna construction consist of two dipole antennas in cross formation, which makes the reader less sensitive to tag orientation.
The nominal reading range is 3m. The reading range is shorter in a stock-take situation. In this use case, it is good to keep in mind that it is not recommended to be too close to the items being read in order to get the best and fastest results. A good rule of thumb is that if you are right next to a rack of clothes, you should take two small steps backwards to gain optimal read.
The user operating the unit blocks the RF signal from the reader antenna (the human body contains water, which attenuates RF signal). Tags behind the user are not read as easily as the ones in front of the unit.
Picture 2. The read pattern from the side and from above and how a human being affects it.
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A directive UHF RFID antenna
A directive antenna radiates power the most efficiently straight ahead from the antenna. The antenna construction consists of two dipole antennas in cross formation which makes the reader less sensitive to tag orientation.
The nominal reading range is 5m. In this use case, it is good to keep in mind that it is not recommended to be too close to the items being read in order to get the best and fastest results. A good rule of thumb is that if you are right next to a rack of clothes, you should take two steps backwards to gain optimal read.
The user operating the unit blocks the RF signal from the reader antenna (the human body contains water, which attenuates RF signal). Tags behind the user are not read as easily as the ones in front of the unit.
Want to also understand how to optimize your reader’s battery life and power consumption? Read our expert article.