A “linear polarization” antenna focuses radio energy from the reader in one orientation (or polarity). This makes it possible to increase the reading distance, being able to increase the penetration capacity of the emitted radio wave.

“Circular-polarized” antennas emit radio waves in a circular manner. In this way, the range of the reader is less but there are more chances to “hit” the tag; in fact, the latter type of antenna is used in situations where the tags applied on the products cannot be controlled, whereas in case of readers equipped with “Linear-polarized” antenna, the tags will have to be aligned in the direction of the antenna itself.

The available host-side interfaces are the most common and include: Ethernet RJ45, USB, RS232, RS485, TTL, Wi-Fi, GPRS, TTL/RS232. Also available are various models of controllers with Input, Output and relay, micro integrated controllers for embedded application development.

RFID devices emit radio waves, very low frequency electromagnetic waves, harmless to the human body.

Even a normal television or an old radio emit electromagnetic waves, so for more than half a century humans have been living with electromagnetic waves of any kind without any health damage having ever been certified.

Active RFID technology uses six different solutions based on different operating principles:

• Response-typeactive RFID technology (similar to Telepass),
• Broadcastactive RFID technology (the tag is a radio transmitter)
• “Wake Up” type active RFID technology (the tag is awakened by a passive low frequency electromagnetic field, but responds/transmits using the energy provided by the battery at UHF 868 MHz frequency)
• RTLS(Real Time Location System)
• WIFI Location System
• Wireless Sensor Network

These are the main features of each solution.

The tag, transponder, active contains within it a small battery that powers communication. The electro-magnetic field emitted by the reader and antenna activates the tag, which, thanks to the energy provided by the battery, begins to transmit outside the same field, reaching high communication distances (even over 100 mt).
Response-type active tags are typically read-write, with memory capacity ranging from 64 bytes to 32Kbytes; they may have an LED light that illuminates when communication is activated and can be “queried,” to check the “state of charge ” of the battery.
There are Response type tags with integrated sensors (or with external probes attached) suitable for detecting temperature and/or a change in state. An example of a well-known active tag and quite similar to Response technology is Telepass.

The active Broadcast tag is in fact a “radio-transmitter: the transmission of the UID code can occur at regular intervals, varying from 0.5 msec to 20 sec (a setting that must be defined at the origin, also called the ping-rate).
Unlike Response technology, the tag does not have to be solicited to activate communication: this facilitates its use in cases where there are particular “barriers” (e.g., metal plates, metal grids, water) that overlap the possible communication between tag and receiver. Broadcast-type tags, for the same transmission distance, are cheaper than Response-type tags however, in contrast, they are read-only (they have the ability to store 9 bytes only the first time), have no LED light, and cannot transmit information related to battery status.
Battery life depends on the ping-rate, i.e., the time frequency of message sending.

Wake Up technology makes it possible to determine the exact position of the tag (and thus of the object, person or vehicle to which it refers) at the moment it is detected by a Position Marker (wake up). The tag has a dual technology: active UHF 868 Mhz and passive LF 125 Khz: when the tag transits close to the Position Marker (from 0.50 mt to 5 mt), the latter’s identification code is “stored” in the Tag and sent to a receiver in Response or Broadcast mode according to need and tag type.

The RTLS system normally operates on Ultra Wide Band and enables real-time detection of the movement of objects and subjects with active tags, detecting their exact location.
Localization can be carried out even if the objects-subjects are moving with a high speed of movement, and the communication distance can be very large (180 m to 500 m). The accuracy of detection depends greatly on the environment.

The WiFi Location System makes it possible to manage the localization and monitoring activities of WiFi devices (devices and/or transponder tags) by taking advantage of any existing communication infrastructure (Access Point). Location accuracy can reach measurements ranging from 2 to 10 mt. Some WiFi Location Systems integrate the interface to GPS technology right from their implementation: this function becomes essential to overcome the limitations of WiFi technology use, especially when deployed in open spaces (yards) where adverse weather conditions (rain, snow, fog) can compromise localization accuracy.

Wireless Sensor Networks are networks composed of small electronic devices that collect and transmit data to each other to locate their position in real time and to measure physical data in certain areas and environments. In most cases a WSN can be easily moved no cabling costs are required. Wireless sensor networks typically operate on frequencies of 868 Mhz and/or 2.4 GHz and enable real-time (indoor-outdoor) location of tagged individuals, as well as, if required, also monitoring of their activity (kinematics) with 3D-type (multi-floor) surveys. The most widely used standard for this technology is Zigbee.

These are procedures to handle the reading of multiple tags simultaneously because they prevent the problem of overlapping radio waves, emitted by different tags, that end up disturbing each other. Within a single electromagnetic field generated by a single antenna of a reader, it is possible to manage the reading of different tags thanks to algorithms called precisely anti-collision, which regulate the time intervals in which they are to be read. This way there is no interference and no risk of receiving incorrect or inaccurate information.