In RFID (Radio Frequency Identification) technology, intelligent and unique identifiers are viable to embed digital growth in items. Without these identifiers, there’s no way for RFID tags to identify objects. These unique identifiers are known as RFID tags that operate on different frequency ranges according to the demands of applications. Not only frequency ranges, but the RFID tags also come in different sizes, shapes, dimensions to acquire the form of paper, objects, buttons, keys and much more. Antenna, microchip and battery are the essential elements of these RFID tags. They are further classified into three types; active, passive and semi-passive. In today’s blog, we discuss RFID tag types and compare them based on frequency, performance, speed and usage.
Before moving ahead, users must know the functions of basic elements of RFID tags;
- Antenna: the purpose of the antenna in an RFID tag is to communicate with the RFID reader.
- Microchip: it acts as a storage of RFID tag. It keeps the record of data or identification number.
- Battery: some tags contain a battery to power the microchip required for reading/writing functionalities.
Now, let’s begin with RFID tag types;
Active RFID Tags
Active tags are the tags that don’t require an interrogator for a power source. The integrated circuit (IC) of these tags contains battery, transmitter, power processing unit. The battery is vital to power the IC and transmitter. Thus, it doesn’t want interrogator for power and transmitting the radio signals; instead, it exploits battery to communicate with the reader via radio signals. Additional processing unit comes handy when internal sensors of active tags need to setup connection with external sensors of the other active tags or surroundings.
The active tags range from 300 to 750 feet. Although active tags are essential for applications that require longer read ranges, they are also vulnerable to radio intrusion and noise interference. The size, weight and price of active tags are more comprehensive than other tags. Another disadvantage of active tags is that their life duration is less than passive and semi-passive tags.
Passive RFID Tags
Unlike active tags, passive RFID tags don’t contain power sources on IC. It depends on the interrogator for a power source. The radio waves emitted by interrogators are the source of power for passive tags. As these tags don’t have their power source, they are limited in terms of functionalities. The board of passive tags doesn’t contain active transmitters; as a result, they are less expose to radio intrusion.
Passive RFID tags operate at low, high and ultra-high frequencies. Inductive coupling is mandatory for tags operating at low and high frequencies, whereas radiative coupling is vital for tags operating above high frequencies. The read range of former tags is 2 feet only, and the read range of later one is equal and more than 20 feet.
Passive tags only work when it is required; therefore, the life of these tags is better, and the absence of an active transmitter along with battery reduces the failure ratio of the IC. They are simple, cost-effective and reliable tags.
On the downside, passive tags have limited storage and don’t have the potential for adding additional characteristics. Due to their simple nature, they don’t attach any temperature, pressure, light sensors like active tags.
Semi-passive RFID Tags
The integrated circuit (IC) of semi-active tags contains a battery and exploits the backscattering mechanism to communicate with the interrogator. Similar to passive tags, their ICs don’t have an active transmitter. The absence of active transmitter makes them invulnerable towards radio interference, but the presence of battery allows them to embed environmental sensors and offers longer read ranges compared to passive tags. In other words, we can say that these are the evolution and enhanced version of passive tags as they may read up to 100 feet.
On the flip side, semi-passive or battery-assisted tags (BATs) are costly, temperature-sensitive, large in size or weight and have limited life duration compared to passive tags.
The table below shows a comparison between RFID tags.
Table 1: Comparison Between Active, Passive and Semi-passive Tags
Number | Characteristics/Name of Tag | Active Tags | Passive Tags | Semi-passive Tags |
1. | Battery | Yes | No | Yes |
2. | Active transmitter | Yes | No | No |
3. | Range | 300-750 feet | 20 feet | 100 feet |
4. | Radio interference | Yes | No | No |
5. | Environmental sensitive | Yes | No | Yes |
6. | Storage space | High capacity | Limited | Larger than passive tags |
7. | Life span | 2-7 years | 20 years | 2-7 years |
8. | Sensors and additional features | Yes | No | Yes |
9. | Size, weight | Large | Small | Larger than passive tags |
10. | Cost | Highly Expensive | Cheap | Expensive |
