RFID Active Tags

Active systems use two main frequencies – 433 MHz and 2.45 GHz. The choice of frequency depends on the user preference, the tag selection, or the environmental factors. Most applications use the 433 MHz frequency because it has a longer wavelength that can work better with materials that are not friendly to radio frequency, such as metal and water. Active RFID systems consist of three essential parts – a reader or interrogator, an antenna, and a tag. Active RFID tags have their own power source – an internal battery that gives them long read ranges and large memory banks. Active RFID tags usually have a battery life of 3 - 5 years, but they need to be replaced when the battery fails. Replaceable batteries will be a cost-saving option as the active tag market matures. The system’s functionality relies entirely on the type of tag used for the application. Active RFID tags can be classified into two types: transponders and beacons. Transponders - These tags work by responding to a signal from the reader, just like passive systems. The reader sends a signal first, and then the active transponder sends back the relevant information. Transponder tags are efficient because they save battery life when they are out of the reader's range. Active RFID transponders are commonly used for secure access control and toll booth payment systems. Beacons - These tags work by broadcasting their specific information every 3 - 5 seconds, without waiting for a signal from the reader. Hence, they are called beacons. Beacon tags are very common in the oil and gas industry, as well as mining and cargo tracking applications. Beacon tags can be read from hundreds of meters away, but they may adjust their transmit power to lower levels to achieve around 100 meters read range and conserve battery life. Most active RFID tags have to endure harsh environmental conditions such as extreme temperatures and moisture. Therefore, they are usually encased in a rugged shell. Due to the size of the battery, circuitry, and durable exterior, active RFID tags are typically much larger than passive tags. Moreover, some active tags may have sensors that monitor environmental parameters such as moisture levels, temperature, and other key indicators for their application. All these additional features increase the costs for the customer, but the benefits of a system may justify the initial investment. The prices of active RFID tags vary from $35 to $150+ depending on the tag's resistance to harsh conditions and other key functional features. Because of the high investment required for an active RFID system, active tags are usually reserved for tracking high-value assets.