RFID technology System overview

RFID tags

There are 3 main features that are assessed by TrailerTrailers RFID consultants when evaluating suitable RFID tags. We summarise these main features into frequency, power and operation. Here is an overview of some of the more important characteristics of each of these areas;

RFID frequencies

RFID - Low frequency

Most commonly used for access control, animal tracking and asset tracking. Advantages are cost. (125khz/134khz)

RFID - High frequency

Used where medium data rate and read ranges up to about 1.5 meters are for acceptable for passive tagging. This frequency also has the advantage of being less susceptible to interference from the presence of water or metals. (13.56 MHz)

RFID - Ultra high frequency

Offers the longest read ranges of up to approximately 3 meters for passive tags and 100 metres for active tags. Relatively high reading speeds can be achieved with these frequencies. (850 MHz to 950 MHz)
RFID 915 Mhz
A particular frequency that is growing popularity due to its potential low costs because of the potential lack of an expensive copper antenna coil, longer read rangers and high read rates. Some of the drawbacks of 915 MHz tags are the degraded performance in the vicinity of water.
RFID readers
RFID readers as the name suggests read information from the RFID tags, the nature of the readers vary greatly depending on the type of tag used in your application. It is possible that some readers can read different types of tags from different manufacturers thereby allowing different tags for different types of asset. This may be an important consideration when Trailer Trailers design a system that will be compatible with future requirements and technology.
Some RFID reader transmit a RF signal in order to energise a passive tag so that it can be read by a different part of the reader system.
RFID chips
RFID chips is another term for RFID tags, for further information on RFID chips please read the sections on RFID tags.

Active RFID tags
These tags have a small battery built into the tags, batteries can sometimes be replaceable or the unit will be replaced after certain time, normally between 1 year and 7 years.
The advantages and disadvantages of active tags can be summarised as follows;
· The active RFID tag cannot function without battery power, therefore they have a limited lifetime.
· More information can be read and written to the tag
· The active RFID tag is typically more expensive, costs typically start from $10 to $20 per tag
· The active RFID tag is physically larger and can be more fragile and prone to damage.
· Read and write distances are much greater than for passive tags
· Active tags can be connected to sensors, eg they could measure and log information such as temperature.

RFID passive tags
Passive RFID tags rely on moving through an area of radio waves in proximity to a RFID reader. The tag draws tiny amounts of power from the magnetic field associated with the radio waves created by the reader, these tiny amounts of energy temporarily energise circuits in the tag. The tag then sends the information encoded in the tag's memory, often using a different frequency to the one used to energising the chip.

The main advantages and disadvantages of passive RFID tags are:
· The tag can be read only at very short distances, typically a few feet at most although some modern tags can operate up to 3m if care is taken with tag orientation.
· The tag is readable for a very long time.
· Passive tags are generally more resistant to corrosion and physical damage.
· The tag functions without a battery; these tags have a useful life of twenty years or more.
· The tag is typically much less expensive, you can typically expect to pay between 10cents and a few dollars.
· The tag is much smaller and it can be easily concealed
· Passive tags have many more potential uses due to reduced size and cost
Semi-active or semi-passive RFID tags
A variety of options exists for this class of tags. These tags use a combination of batteries,(normally used to run the chips circuits) and an induced current to transmit data to the RFID reader.
The main advantages of these tags are that they achieve longer read ranges than passive tags but generally at lower costs than active tags.

RFID operation
Read only RFID tags
Are programmed with unique information stored on them during the manufacturing process – often referred to as a ‘number plate’ application. The information on read-only chips can not be changed.

Read and Write RFID tags
The system can add information to the tag or write over existing
information when the tag is within range of the reader. Read-Write chips are more expensive that Read Only chips. Applications for these may include field service maintenance or ‘item attendant data’ – where a maintenance record associated with a mechanical component is stored and updated on a tag attached to the component. Another method used is something called a "WORM" chip (Write Once Read Many). It can be written once and then becomes "Read Only" afterwards

 

 

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