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RFID basics

What is RFID.

RFID is short for Radio Frequency Identification. Generally a RFID system consists of 2 parts.  A Reader,
and one or more Transponders, also known as Tags. RFID systems evolved from barcode labels as a
means to automatically identify and track products and people. You will be generally familiar with RFID
systems as seen in:
  • Access Control.
    RFID Readers placed at entrances that require a person to pass their proximity card (RF tag) to be
    "read' before the access can be made.
  • Contactless Payment Systems.
    RFID tags used to carry payment information. RFIDs are particular suited to electronic Toll collection
    systems. Tags attached to vehicles, or carried by people transmit payment information to a fixed
    reader attached to a Toll station. Payments are then routinely deducted from a users account, or
    information is changed directly on the RFID tag.
  • Product Tracking and Inventory Control. RFID systems are commonly used to track and record the
    movement of ordinary items such as library books, clothes, factory pallets, electrical goods and numerous

How do RFIDs work.

Shown below is a typical RFID system. In every RFID system the transponder Tags contain information.
This information can be as little as a single binary bit , or be a large array of bits representing such things
as an identity code, personal medical information, or literally any type of information that can be stored in
digital binary format.

basic RFID system

Shown is a RFID transceiver that communicates with a passive Tag. Passive tags have no power source of
their own and instead derive power from the incident electromagnetic field. Commonly the heart of each tag
is a microchip. When the Tag enters the generated RF field it is able to draw enough power from the field to
access its internal memory and transmit its stored information.
When the transponder Tag draws power in this way the resultant interaction of the RF fields causes the voltage
at the transceiver antenna to drop in value. This effect is utilized by the Tag to communicate its information to
the reader. The Tag is able to control the amount of power drawn from the field and by doing so it can modulate
the voltage sensed at the Transceiver according to the bit pattern it wishes to transmit.

Types of RFID Transponders.

There are three types of Transponders. Tags are either Active, Passive, or Semi-passive Transponders.
As already mentioned, Passive Transponders have no internal power source. They draw their power from the
electromagnetic field generated by the RFID reader. They have no active transmitter and rely on altering the
RF field from the transceiver in a way that the reader can detect.

Active transponders have their own transmitters and power source, usually in the form of a small battery. As a
result of this they are able to be detected at a greater range than Passive ones. Active Tags remain in a low
power "idle" state until they detect the presence of the RF field being sent by the Reader. When the Tag
leaves the area of the Reader it again powers down to its idle state to conserve its battery.

Semi-Passive Transponders have their own power source that powers the microchip only. They have no
transmitter and as with Passive tags they rely on altering the RF field from the Transceiver to transmit their

Designing a RFID system.

Priority 1 Design have a range of RFID products available to those wishing to design and construct their own
RFID systems, We also carry RFID modules for OEM users wanting to quickly incorporate existing products
into their own design. Custom designed systems can also be tailor made to suit your individual requirements.
Contact our design department to find out how.

RFID reader module

Priority 1 Design manufacture and stock low cost RFID reader and writer
modules. These modules are suitable for reading EM4100 and T5557
compatible RFID transponders.
Learn more about our a RFID reader and writer modules.

RFID keyfob 125Khz EM4100 compatible
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This low cost proximity keytag is suited for our RFID Reader module as well
as any standard RFID reader that can read EM4100 compatible RFID
transponders. See the specifications for this item.
Want to design your own reader and need to know about EM4100
compatible Transponders? Click here to learn more about the EM4100
protocol and common encoding schemes used in RFID systems.
125khz RFID proximity card
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This low cost proximity card is suited for our RFID Reader module
as well as any standard RFID reader that can read EM4100
compatible RFID transponders.

View Proximity card Specifications   Learn about EM4100 protocol
t5557 rfid transponder
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We carry a stock of T5557 RFID transponders. These tags carry 224bits
of Read / Write data, and are suitable for our RFIDREAD-RW reader writer

See T5557 RFID transponder to learn about reading and writing RFID tags.

EM4095 RFID front end chip.
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We routinely manufacture RFID readers and products. At the heart of
our RFID readers is the EM4095 Read/Write front end chip. We carry a
stock of these IC's which are available through our On-line Shop.
Learn more about designing with the EM4095 chip.

As an alternative we also carry the ATMEL U2270B rfid front end chip.
Learn more about designing with the U2270B chip.

rfid coil antenna design
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A critical component of any RFID system is the RFID coil antenna. We keep a stock of RFID coil antennas as they form a core element of our RFID readers. For the convenience of hobbyists and professionals alike you can buy RFID coil antennas direct from our on-line shop.
Learn more about our RFID coils 

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