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Double effect! Consistent RFID performance in near field and long-distance range

Articles | By deister electronic | 11 January 2017
A dual technology by Deister Electronic unites HF and UHF in one access card A dual technology by Deister Electronic unites HF and UHF in one access card

A dual technology by Deister Electronic unites HF and UHF in one access card

RFID is a key technology in access control today. However, with conventional solutions the user has to carry several RFID cards for different systems. The alternative is using a hybrid card that leads to losses in performance. The ‘DualTechnology‘ solution by Deister Electronic provides a remedy: HF and UHF transponders are installed in the same card without affecting each other. Norman Maaß, developer at Deister Electronic, speaks with “RFID im Blick Global” about the card solution, the increasing demand for it, and the potential of the solution for the migration from HF to UHF.

Norman Maaß, Research & Development Engineer – UHF, Deister Electronic, in an interview with “RFID im Blick Global”

Limited space on the card reduces RFID performance

Norman MaaßNorman Maaß Whether in HF or UHF: the bigger the antenna, the better the transmission performance. For a simple HF or UHF RFID card, this presents no challenge for the developer. When HF and UHF are combined on one card, a space problem arises that reduces the reading rates of both technologies. “When a UHF dipole is mounted into a large HF coil, the dipole is short-circuited and suffers a loss in reception. If both technologies are installed side by side instead, this leads to poorer HF performance, since the antenna has less space. Instead of several centimetres, the range is suddenly only three centimetres.

An additional problem is the transmission power loss of the UHF antenna when it is covered by the hand of the user when they touch the card. A detection range of six to seven meters can be reduced to one meter when the card is handled in the wrong way. Not only does the performance suffer, but the user comfort suffers as well. The ‘DualTechnology‘ solution by Deister Electronic solves performance losses in RFID detection access solutions,” Norman Maaß explains.

Loop design solution from the textile sector leads to breakthrough

But how could Deister Electronic solve the space and transmission power problem? “Usually, card manufacturers can only fall back on already existing transponders or inlays, and then integrate them into the access card with cutbacks in the performance. A customer approached Deister Electronic with the request to integrate a 868 Megahertz UHF RFID transponder for long-range identification into a 13.56 Megahertz HF card for close-range door access. This motivated us to create a high-performance, ease-of-use solution.

The developer team was able to fall back on a solution for textile applications that had been registered for patent approval in 2011, for which the company had developed a loop antenna solution based on a closed UHF dipole antenna. The loop consists of several parallel conductors forming a coil. If the folded dipole developed by Deister Electronic is applied to a ground surface such as a human body, various parts of the antenna are short-circuited, rather than the entire antenna. The other parts of the antenna continue to transmit at optimum performance and are not affected by a connected HF antenna, as first tests have proven in 2013,” Maaß states.

Martin HartwigsenMartin Hartwigsen “The ‘DualTechnology‘ RFID solution by Deister Electronic combines HF and UHF on one card without any interference. Thus, just one card can be used both for the access identification to the premises and for the access control to the building. Neither the two different frequencies nor disturbing factors like a human or metal affect the performance.”

‘DualTechnology‘ solution offers consistent reading performance

The engineer continues: “The HF/UHF access card by Deister Electronic is characterised by user-friendliness and comfort for the user. Numerous solutions from competitors achieve lower reading ranges in access control and can only be retained by the user for a full transmission power at specific points. Due to the lack of UHF reading range, the employee has to approach the reader closely with the vehicle, slowing to a halt in extreme cases, and present the card between the fingertips far away from the body for authentication at the access control point.

Access to the building requires either an additional RFID card or the user may only touch the combination card at specific points and may not carry it close to the body in order to prevent influencing the transmission power. In the ‘DualTechnology‘ solution by Deister Electronic, HF and UHF work side by side without interference and are also not affected in transmission power by interference fields such as a human hand. The solution consists of a single antenna, which uses the maximum surface space of the access card due to the loop structure. It can be used in parallel by both technologies without compromising the performance.”

Regulating the performance via label

“The combination card opens all entrances and access roads to the premises via UHF without the driver having to stop. Access is accelerated. At the same time, the card provides access to the building via HF and can be held as desired or even carried directly on the body. The same applies to windshield transponders on metallised front windows for vehicle identification. A so-called Range Reduction Device (RRD) configures the transmission power of the card or the windshield label by variably reducing parts of the transponder by means of a metal foil sticker to approximately 66 or 33 percent of the performance in order to prevent overreaches. The technology solution prevents nearby vehicles without a metallised front window from being identified as well due to the higher transponder range during the access control.

RRD prevents double, false, or nonreading and guarantees the clear identification of both driver and vehicle. Deister Electronic registers an increasing demand for HF/ UHF combination cards. Permanent or interim solutions are used in companies to realise a migration from HF to UHF in access control. The HF/UHF combination card can also be supplemented by a magnetic strip and a contact chip,” Maaß concludes.

Last modified on Sunday, 15 January 2017 22:37
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