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User effect on RFID reading patterns between different UHF RFID antennas

Different antennas have different 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 a person.

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. 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 (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 effect will still stay about the same. The benefit in this case is that e.g. in a point-of-sales use, the reader will not read any other items than the ones placed on the defined device read area.

Nordic ID Sampo reading range

The picture shows the reading pattern and how a human being affects it from the side and from above.

An omnidirectional UHF RFID antenna

In a certain plane an omnidirectional antenna's reading pattern radiates power equally in every direction. The antenna construction in the Nordic ID Morphic UHF RFID Cross Dipole consists 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 not that much in a stock-take situation but on the other hand, it is not recommendable to be too close to the items being read 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.

Nordic ID Morphic reading range

The picture shows the read pattern and how a human being affects it from the side and from above.

A directive UHF RFID antenna

A directive antenna in the Nordic ID Merlin UHF RFID Cross Dipole 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. The reading range is not that much in a stock-take situation but, on the other hand, it is not recommendable to be too close to the items being read 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.

Nordic ID Merlin reading range

 

The picture shows the reading pattern and how a human being affects it from the side and from above.


Wish you all succesful RFID reading!

2 comments on “User effect on RFID reading patterns between different UHF RFID antennas”

  1. Posted 19 April 2013 at 01:28:47

    What about multipath caused by reflections from a human body and from nearby objects?

  2. Posted 23 April 2013 at 09:23:56

    Hello Robert,

    Here is an answer our engineer gave me:
    The effect of the multipath propagation is seen usually outside the reader “continuous” reading zone. There you can find certain areas where tag(s) can be read and areas where reading is impossible. If one could visualize these areas they would seem as waves in the ocean. There are maximums and minimums depending from the phase differences of the summing signals coming from different routes.

    If antenna is highly directive like Nordic ID Merlin or Nordic ID Sampo antennas then human standing behind the antenna has almost no effect. But with omnidirectional antennas like with the Nordic ID Morphic you can see slightly improvement in reading performance when human body is behind the antenna.

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