How does a dual frequency RFID tag work?

A dual frequency RFID tag is a special type of rfid tag that can worked on 2 different frequency band to meet different requirements.

Normally there are LF ( 125 khz) + HF( 13.56 MHz), or HF + UHF ( 860- 960 MHz). Because they worked at very different frequency , therefore how to make the tag better work with readers are very important.

Traditional dual frequency rfid tag/ card

Traditional way is by using 2 different coiling/ antennas to connect 2 chips to achieve such goal. However, because of parasitic capacity between 2 antennas, the antenna impedance coupling will be disrupted, which lead to deviation of central frequency and decrease of energy transmit efficiency. The chip can not draw sufficient power from electro-magnetic field, and finally lead to non- response or shorter read distance.

Also the antenna shall bind to 2 different chips, this make the total antenna/ tag size very large, meanwhile the displacement of two antennas also make the tag performance unstable and unpredictable.

Dual frequency rfid chip

Because of above reason, the dual frequency rfid chip is created, which provide 2 groups of interface antenna connected into, For example, EM4423, as following illustration, has provided 2 antenna port respectively for HF and UHF.

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Since such chip integrated HF and UHF, so it make the antenna very compact and small, also needn't to considering the affection that antenna brought, even with parasitic impendence, it also can be eliminated by optimizing antennas. Therefore its performance is assured and perform well either in HF and UHF.

A typical dual frequency UHF RFID tag is GEE-NUT-DF20, with HF read distance of 5 cm and UHF read distance of 10 meters.

http://www.geenfc.com/en/Products/UHFTags/dualfrequency/2018-05-02/236.html

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For more info, please contact GEE's engineer for details.

How does a dual frequency RFID tag work?

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