How RFID transponders work

14.03.2019

How does RFID actually work, and what kind of features do transponders require to make it work? This article answers these questions by focusing on RFID’s transponders and their identification capability. If you are a system integrator, your own customers might find the points covered in this discussion helpful.

RFID uses transponders, often called tags, but that also take the form of cards. Transponders are always given specific, unique ID numbers that reside in their chip memory. So-called ‘smart card’ transponders come with additional memory for storing a lot more data than a mere ID number. This memory capacity is often used in payment applications, time- or location-specific access authentication or other applications that demand security or the storage of significant data.

Smart card memory also has the capacity to support highly secure encryption protocols during identification transactions – wherever a transponder’s unique ID number will not be secure enough.

Some RFID readers possess an additional ability, to write data to transponders during transactions. Writing transponders with new data occurs in payment, token or similar applications, where transponders store a limited number of permitted transactions. Each reading transaction will reduce the available number in the transponder which the reader then overwrites to it.

RFID transponders are also divided into active and passive categories, based on their method of communicating with readers. All Idesco transponders are passive transponders without power source. Active transponders have a power source strengthening their transmitting signal between transponder and reader. Active transponders, used for e.g. identifying pallets and railroad cars, enable reading distances of tens of meters. With passive transponders the reading distances are from a few centimeters to fifteen meters. Benefit of passive transponders is their lower price and longer life span compared to active transponders whose life span depends on their power source.

Passive transponders don’t transmit any signals independently. Readers interrogate passive transponders by induction. Passive transponders function only when taken close enough to a reader that can read the specific transponder. Reader sends the data it obtains from transponder to the system for authentication. More advanced transponder technologies, e.g. MIFARE DESFire, are secured with reader and transponder specific security keys. This is called mutual authentication. Transponder can be read only by a specific reader pre-programmed with transponder specific security keys. 128-bit AES encryption ensures DESFire transponders cannot be copied or hacked by any method.

 

Identification technologies and their applications

Passive identification technologies are generally divided by their operating frequency to 125 kHz, 13,56 MHz and UHF technologies. These technologies are either standardized, so called open technologies, or proprietary, so called closed technologies. Open, standardized technology, e.g. smart card technology MIFARE® and UHF technology EPC provide you a wider selection of suppliers when you decide to expand your system with compatible readers and transponders in the future. Closed technology, instead, means that there is only one supplier that can provide you compatible readers and transponders.

With passive UHF technologies identification distances are from a few meters to fifteen meters. UHF technologies are used in vehicle identification and logistics applications, and they are also suitable for person identification in applications where a person who carries a transponder passes access point without need to show the transponder to the reader at close proximity.

125 kHz and 12,35 MHz provide identification distances of few centimeters. These technologies are used for access control and asset marking.

 

Transponder types

There are many types of transponders depending on deployment. RFID transponder can look very different depending in what kind of environments and for which purpose they are intended. RFID transponder can be a keyring, wearable transponder, card or a wristband, and so much more depending on deployment and purpose. Tags attached in different items are often stickers or buttons. Common to all transponders is that they all have an RFID chip inside which is then read by the reader.

Depending on the material, transponders can withstand various, even harsh conditions. In general, RFID transponders, especially transponders especially designed for industrial environments, withstand chemicals, heat, water, dirt and impacts very well. For example, RFID transponders are successfully used for marking clothes requiring regular laundry processing.

For metal surfaces, there are specific, dedicated transponders. Also windshields require special transponders. Transponders dedicated for metal surfaces and windshields may not perform well on other surfaces, so it is crucial to choose the right transponder to each purpose. The further the reader is supposed to read the transponder, the more crucial it is to optimize their position related to each other in your deployment.

Learn about different transponders on Idesco website. Our experts and sales persons are also ready to help you to find a suitable transponder for your deployment.

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