RFID Readers, Writers, and Printers

- overview of RFID, Radio Frequency Identification readers, writers and printers and how their technology operates.

RFID readers, RFID writers and RFID printers are effectively the base connection points used for an RFID system. Often only an RFID read function may be needed and this simplifies the requirements for the item, but at other times both RFID write and read will be needed.

RFID technology allows considerable flexibility in the placement of the RFID readers or RFID transceivers with respect to the RFID tag as line of sight is not a requirement. Barcode systems require a line of sight path to the bar code, and not only does this mean that the items must be visible, but they must also be orientated so that the barcode reader can see and hence read the barcode. RFID readers can be located in a position sufficiently close to the item to allow successful reading. This provides significantly greater flexibility and reliability.

RFID reader elements

The RFID reader can be broken down into a number of major elements or sub-systems:

  • Antenna:   The antenna is an integral element within the RFID reader. The antenna must obviously be tuned to the frequency of operation. It must also be mechanically incorporated into the overall packaging or case design for the RFID reader. For lower frequencies, the RFID reader antenna may comprise a coil, whereas for higher frequencies it may be a form of dipole element. With RFID up to 30 MHz typically using inductive coupling this means that most antennas would comprise a coil, but above this where radiative systems are used and the wavelengths are much shorter, then forms of dipole offer good performance.
  • Controller:   The controller is the area within the RFID reader that provides the control for the system. It will enable the read or read-write processes to be actioned correctly and any protocols that need to be observed will be initiated in this area.

    The complexity of the controllers for RFID readers varies considerably dependent upon the application and the system. Some are particularly simple, whereas others will be considerably more complicated.
  • Network interface:   Once information has been gained from a tag, the RFID reader needs to ensure that the required actions are taken. To achieve this, the RFID reader will normally need to communicate with a central controller. Traditionally RS232 or RS422 interfaces have been used, but now there is much greater use of Ethernet, or wireless systems including Wi-Fi, Bluetooth, or Zigbee.

In addition to these elements there is also software as most items these days have processors which are software driven.

RFID printers

RFID printers are used in conjunction with RFID smart labels. The RFID printers are devices that have the ability to print the label and also programme or write the tag.

There is a wide variety in performance of RFID printers. Some are intended for low volumes RFID label / tag production while others are needed for much higher volumes. Those RFID printers used for low volume label production may require the labels to be applied to the product manually. Others used for high volume production may also have an applicator built into the system.

The RFID reader or reader writer (RFID transceiver) is obviously a key element in any RFID system. It enables the tags to be detected and the data read. While there is not the same level of constraint on the size, they must nevertheless be made relatively compact, and in some circumstances there may be environmental requirements, especially if they are to be operated outside or on vehicles. Accordingly RFID reader design can pose some design challenges.

By Ian Poole


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