Tag info

Radio Frequency Identification Transponders, well known as “RFID tags” have been used in various forms for many years. Airplanes have been using radio transponders to signal and identify themselves to air traffic control radar on the ground since World War II. Transponders, also called “smart chips” are sometimes injected into our pet dogs and cats to positively identify them in case they are lost. Mobil-Exxon gas stations currently issue customers a “Mobil Speed Pass” to charge their purchases and toll road plazas detect vehicle transponder tags to bill appropriate fees for tolls. Within the next ten years or so, most products will have an individual “smart tag” attached to them just as they currently have a UPC bar code printed on their labels today.
There are numerous types of transponders; each designed for a specific application. Here we will attempt to categorize them and provide a lay explanation of their functions.

The range performance that can realistically be attained with RFID devices varies widely depending on a number of variables. Range depends on power level of the reader, efficiency of the antenna, transponder frequency, size and relative orientation of the devices, ambient electrical and magnetic noise present and the proximity to various materials, just to name a few.

Manufacturer’s data sheets tend to optimistically predict the performance of their devices. EasyLogics engineers have tested a wide range of products and are willing to share the data we have collected to give you a realistic feel for what is to be expected using RFID transponders.

Please give us a call when you require further assistance.

Passive Transponders
A transponder is said to be “passive” if it does not contain its own power source. The passive transponder picks up power from a nearby electric or magnetic field provided by a reader. The reader interrogates the adjacent field for transponders that may be in its proximity and induces enough energy into the transponder’s electronic circuitry that it wakes up and transmits back to the reader its identification number as well as any additional data it may have stored in its memory.

The advantage of the passive transponder is that they are low cost, small and they virtually never require a battery change. The disadvantage is that they have relatively limited range. It is ideal for an identification label that will be scanned at close proximity. It is typically not a good solution for the detection of vehicles approaching a security checkpoint.

A "foil" or "inlay" is generally used to describe a High Frequency or Ultra High Frequency tag that is very thin, the thickness of a piece of paper that is a piece of plastic with the antenna and integrated circuit imbedded in it. It is NOT a "label". A "label" is much more expensive and includes an inlay AND a label on top of the inlay (usually white like a traditional printer label) as well as an adhesive bottom on the inlay. In essence, the inlay is embedded within a traditional printer label.

Active Transponders
A transponder is said to be “active” if it contains its own power source. The active transponder will “ping” its identification periodically and the reader will listen for any transponders in the field. If the active transponder pings quite often it will be heard quickly and detected. The more frequent the ping the faster its battery will expire. If the transponder pings “now and then” there will be some delay until its detected, however the battery will last longer.

The advantage of the active transponder is that it has relatively longer range. This attribute could also be a problem if the range is too great and checkpoints allow passage of a vehicle not even approaching, but just passing by in the area. The disadvantage of active transponders is that they are larger, more costly and have a relatively short battery life. Active transponders may not be a good solution for the detection of vehicles approaching a security checkpoint as the battery life may be less than expected. Active tags are good for asset tracking and personnel tracking, as long as the cost is justified for the tag (€25-€30) .

Semi-Active Transponders
A transponder is said to “semi-active” if it contains is own power source that is subsequently turned on by an integral passive transponder circuit receiving its energy from the reader’s interrogation. An example of a semi-active transponder device is used as part of the E-Pass System (Electronic Toll Booth Collection System). Another example of Semi-Active Transponders is the Shell Pin at Gasstation system.

Semi-Passive Transponders
A transponder is said to be “semi-passive” if it contains its own power source used for its internal control circuitry but not used for its transmitter power. Its transmit power will be energy reflected back, or “backscattered”, from the reader as it attempts to interrogate it. Here is an analogy that may help in understanding “backscatter”.

Two boy scouts are out on a camping trip. One scout stays at the cabin and the other ventures out into the woods. They stay in contact by signaling Morse code between each other using their flashlights. After a few hours of communicating their batteries are dead. This method is analogous to active transponders signaling.

Next, they devise this new scheme to keep communicating without using up batteries so fast. They put this powerful beacon on the roof of the cabin and plug it into the house power. The beacon shines into the woods and signals to the scout on foot. The cabin scout codes his message and then leaves the beacon on steady. The foot scout then decodes his message; the replies by using a hand held mirror reflecting back the cabin beacon’s energy. The only energy the scout needed was the small amount of power needed to move the mirror. The light energy was provided by the cabin power.

This technique is known as “semi-passive backscatter”. Its advantage over active transponders is relatively lower cost and size and its battery life is much improved. Its range is improved over passive transponders but is controlled to an optimum distance for vehicles approaching a checkpoint.

125 kHz LF tags / transponders

Low Frequency, passive, RFID transponders have been successfully deployed in automatic data collection applications for well over 20 years. They are by far the most popular family of RFID devices. Although other more modern RFID technologies have threatened to obsolete LF tags they not as yet put a dent in their popularity.

Many “LF” transponders operate at 125 kHz, however all Texas Instruments LF RFID operates at nearby 134.2 kHz. These devices operate on the principle of magnetic inductive coupling, much like that the primary-secondary winding pair of a power transformer. Although they are classified as Radio Frequency Identification devices they actually employ magnetic coupling rather than conventional radio principles.

LF RFID tags are more suited to use near liquid and metallic environments, as compared with high frequency or UHF devices. LF devices typically can only be read when only one transponder is in the field at a time. LF devices typically do not have anti-collision properties. The type of LF transponder you will choose will depend greatly on the type of project you are undertaking. Selecting the tag is just as important as the type of reader and antenna you are seeking. EasyLogic carries wide a variety of different tags for virtually any project.

We carry many varieties of LF transponders ranging from the small 23/32mm glass transponders (used in animal tracking, race timing, etc.) to the large 85mm disk transponders (used in automobile tracking) to the specialized mount-on-metal transponders that are specifically detuned to be used on metal surfaces.

13 MHz HF tags / transponders

High Frequency passive RFID Transponders typically are composed of a “foil”, or “inlay”, or “inlet” that is placed inside a packaged enclosure of sorts. These transponders operate at 13.56 MHz. There are also "labels" in which the inlay is embedded within a printing label and can be printed on and adhered to a product. Labels are generally 2-3 times as expensive as raw foil inlays due to the process involved with embedding the inlay within the label.

A silicon chip and its associated storage capacitor are affixed to a PET plastic substrate. The substrate usually contains an etched metalized antenna. This passive circuit obtains its power to operate from electrical currents induced in its antenna coil from nearby RFID Reader systems. The chip detects an interrogation and replies with its associated data stored within its memory. These chips usually have read and write capability.

High Frequency RFID foils are converted into to usable products such as labels, cards, tickets and identification bracelets. A particularly unique High Frequency device is the Texas Instruments “encapsulated” High Frequency Transponder that actually uses a rugged wire wound coil for its antenna structure. These tags are made to sustain the riggers of industrial laundry processes.

Choosing the proper High Frequency Transponder for your High Frequency RFID system is a complex task. Easyogic carries a number of high frequency products, including labels, ID cards, wrist bands, tickets and laundry tags . Please call us to help you  selecting the proper RFID transponders for your application.