RFID technology is very popular in a variety of industries that use physical assets as a means of trade. We use this technology in fields like manufacturing, warehouses, retail, construction, healthcare, education, etc. Making it an almost essential component of business in modern times. RFID signals communicate using radio waves in two different methods. In short, depending on the distance between the reader & the tag, they can use near-field or far-field communication.
Today, we will be discussing the difference between Near-Field and Far-Field in antenna.
What is Near-Field & Far-Field?
RFID readers use radio signals to transmit instructions & receive data from the tags. Whenever a tag enters the electromagnetic field of the reader, it transmits data to the reader using two methods, depending on the distance. This distance classifies a reader’s broadcast field into two types.
As the name suggests, Near-Field refers to the immediate area next to the antenna. NFC (Near-Field Communication) tags usually need to be within 10 cm of the reader to work. Near-Field readers work through the principle of inductive coupling. Coupling refers to the wireless connection between a tag and a reader. Inductive coupling works through wireless transfer to energy. In short, when a tag enters the NFC field, the radio signals from the reader induced an electric current within the antenna of the tag. The tag then uses this energy to broadcast back a signal of its own.
In the case of Far-Field antennas, the distance between the tag to too much to transfer energy wirelessly. So, instead of electric induction, these tags rely on radiative coupling. This phenomenon works based on a technique called backscattering. In short, when an RFID tag enters the far field of an antenna, the signals radiating from the antennas hits the tag. A part of this signal is reflected (backscattering) back to the reader, transmitting the data.
Comparative Assessment of Near-Field & Far-Field Antennas
Now that you know the difference between near-field & far-field, let’s discuss the benefits & disadvantages of both systems.
Read Range
As the name suggests, NFC has a very short range, although the signal can go as far as a couple of meters. But, for inductive coupling to take place, the tag and reader must be within 10 cm. For Far-Field communication, the read range can be as much as 30 – 40 meters, in the case of UHF passive tags. And even more than 100 meters, in the case of active RFID tags.
Communication Channels
This depends on the method of coupling that the reader uses to communicate with the tag. NFC tags have a two-way communication channel, this is because the tag broadcasts its signal using inductive coupling. But far-field tags can only transmit already programmed data through backscattering. In short, tags can only be reprogrammed when they are inside the near-field.
Storage Capacity
NFC tags are specifically designed to only operate within the near field. They operate on low frequency and can hold a lot more data than standard RFID tags. They can hold up to 4 KB, as opposed to standard RFID tags that usually hold 512 bits.
Conclusion
Now that you’ve reached this far, you probably know everything you need about near-field and far-field. Using either one for coupling with a tag has its advantages & disadvantages. For example, if the volume of tags is high and spread in a wider area, you will have to rely on far-field antennas. This is done in retail shops, warehouses, manufacturing, etc for asset tracking & inventory management. However, if you want to reprogram an RFID tag or only read a single tag without interference from surrounding tags, then it’s best to use near-field antennas. This is due to the fact, an antenna will receive and read signals from every tag within its read range.
So, before selecting an antenna for yourself, make sure to keep these factors in mind. Before we end this blog, let’s check out the applications of both systems.
Applications
There are different applications for both far-field and near-field communication in an RFID system. So, let’s check out a couple of them.
Near-Field Antenna
(A). Billing Counter
(B). RFID Tag Programming
(C). Access Control Gate
(D). Public Transportation
(E). ATM/Credit Cards
Far-Field Antenna
(A). Asset Tracking
(B). Inventory Keeping
(C). Item Security/Security Gates
(D). Supply Chain Management
(E). Assembly Line Monitoring
Frequently Asked Questions
Q1. What is the far-field of the antenna?
Ans. As the name suggests, it’s the farther region of an antenna’s broadcast field, beginning at the endpoint of the near field. Tags can only communicate with readers using radiative coupling in this zone.
Q2. Is card NFC or RFID?
Ans. Cards are used for security purposes, like providing access to authorized personnel, access bank accounts, and security gates on public transportation. Thus, they need to be only readable in close proximity to an RFID reader. Therefore, most cards operate using NFC (Near-Field Communication).
Q3. Is RFID unidirectional?
Ans. Unlike NFC, traditional RFID systems are unidirectional, as the tag only broadcasts/backscatters data to the reader. The reader’s signal doesn’t communicate any information, rather, it just activates the tag. Making it a unidirectional system of communication.
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