What is RFID Technology?
RFID (Radio Frequency Identification) is a technology that is working on radio frequency of radio waves. This technology is used to automatically identifying the object or tracking the objects. Now, here this object could be anything, like it could be the books in a library, any items that are purchasing from the shopping mall, the inventory in the warehouse, maybe your own car, and even the animals as well as the birds.
In this RFID technology, the RFID tag is used to get attached to the object when he wants to track. So, RFID reader is continuously sending radio waves. So, whenever this object is in the range of the reader then this RFID tag is used to transmit its feedback signal to the reader.
So, it is very similar to the technology which is used in a barcode. But in case of a barcode, the object and the scanner should be in the line of sight. As this RFID technology is not a line of sight technology, so as far as this object is within the range of the reader, the object is able to identify the reader and it is able to send the feedback signal back to the reader. So, by using RFID technology we can track multiple objects at the same time.
What is inside the RFID system?
As we have already discussed, the RFID system contains two components.
- RFID Reader.
- RFID Tag.
Now, these RFID tags are also coming in many ways. This RFID tag could be an active tag, it could be a passive tag or it could be a semi-passive tag.
These passive tags do not have their own power supply. So this passive tag relies on the radio waves which is coming from the RFID reader for the source of energy.
While in the case of a semi-passive tag, they used to have their own power supply. But for transmitting the feedback signal to the RFID reader they used to rely on the signal which is coming from the RFID reader.
While in the case of an active tag, they used to have their own power supply. But for transmitting the signal back to the reader also they are relying on their own power supply.
So, as these passive tags do not have their own power supply, So the range is less compared to the active and semi-passive tags.
- RFID Reader
These RFID readers are coming in many sizes and shapes. So this RFID reader could be as large as the size of the door which normally sees inside the shopping malls or it could be your handheld reader. RFID reader mainly consists of three components.
The first component of the RFID is an RF signal generator. This signal generator generates radio waves that are transmitted using the antenna. Also to receive feedback signal which is coming from the tag, the RFID reader also has a receiver of the signal detector and to process the information which is being sent by the RFID tag, this RFID reader also has a microcontroller or many times this RFID reader is directly connected to the computer.
- RFID Tag
Now let’s see the RFID tags, so most of the tags, which are being used today are passive tags because these passive tags are quite cheaper compared to the active tags, as well as, as they do not quite require any power source, so they are quite compact. So these passive tags are also coming in many forms.
So these passive tags could be either the size of a key chain or it could be the size of a credit card or maybe it could be in the form of a label.
So let’s see what are the basic components inside this RFID tag. So, the first component that you see inside the RFID tag is a transponder that receives the radio waves which are coming from the reader and send the feedback signal back to the reader. As the passive tags do not have their own supply so they rely on the radio waves which are coming from the reader. So they used to get the energy from the radio waves which are coming from the reader.
So, using this rectifier circuit the energy that is coming from the radio waves is stored across the capacitor. And the energy is used as a supply for the controller as well as the memory element inside is RFID tag.
Frequencies of RFID Tag
Let us the different frequencies at which these RFID tags are operated. So, mainly this RFID tag is operated at three frequencies.
- The low-Frequency range(125 KHz or 134 KHz).
- The high-frequency range(13.56 MHz).
- The ultra-high-frequency range(860-960 MHz).
This frequency range or frequency of operation varies with country to country but the majority of the countries use to follow these frequencies for the operation for the RFID tags.
So, as these low frequencies signals can travel a very short distance, so the range of the RFID tags which is using this low-frequency range is up to 10 cm, and high frequencies radio waves can travel up to the 1 meter while the ultra high frequency can travel up to 15 meters.
Working principle for RFID Tag
Now, let us see the working principle for this RFID tag. This working principle also depends upon the frequency of operation. So, for the low frequency and the high-frequency operation, the working principle is based on the inductive coupling. While in case of an ultra-high frequency RFID tags, the working principle is based on the electromagnetic coupling.
- Working Principle for Low and High-Frequency
First of all, let’s see the working principle for this low-frequency and high-frequency RFID tags. So, as I said earlier, this RFID reader continuously sending radio waves with a particular frequency.
Now, this radio waves which is being sent by this RFID reader serves three purposes.
First, it induces enough power into the passive tag. Second, it provides the synchronization clock for the passive tag, and Third, it acts as a carrier for the data which is coming back from the RFID tags. So, these are the basic 3 purposes that are being served by the radio waves that are sent by this RFID reader.
So, in case of low frequency and high-frequency operation as an RFID reader and tag are very close to each other, so the working principle is based on the inductive coupling. So, the field which is generated by this RFID reader used to get a couple with the antenna of an RFID tag and because of this mutual coupling, the voltage will get induce across the coil of RFID tag. Now some portion of this voltage is getting rectified and used as a power supply for the controller as well as the memory elements.
As the RFID reader is sending a radio wave of a particular frequency, so the voltage that is induced across the coil is also of a particular frequency. So this induced voltage is also used to derive the synchronization clock for the controller. So now suppose if we connect a load across this coil, then current will start flowing through this load and if we change the impedance of this load then the current that is flowing through this load will also get changed.
Now suppose if we switch on and off this load then the current will also get switched on and off. So, this switching of current or rate of change of current also generates a voltage in an RFID reader. SO this switching on and off the load is known as the load modulation.
Now suppose, if we switch on and off this load according to the data that is stored inside this RFID tag, then that data can be read by the RFID Reader in the form of a voltage. So, in this way using this load modulation we are changing the voltage that is generated across the RFID reader coil. And in this way, we are generating modulation on a carrier frequency. In this way in a low frequency and high-frequency RFID tags, using this load modulation technique the data is being sent back to the RFID reader.
- Working Principle for Ultra High Frequency
Now, let us see the working principle for the ultra high frequency. In the case of Ultra high frequency, as a distance between the reader and the tag is up to a few meters, so the coupling between the reader and the coil will be the Fire Field Coupling. So, this RFID reader continuously sending the radio waves of a particular frequency towards the tag, and in response, this tag is sending a weak signal to the RFID reader.
Now this weak signal which is being sent back to the RFID reader is known as the backscattered signal. The frequency of this backscattered signal depends upon the load matching across the coil. So if the load is matched exactly, then the intensity of the backscattered signal will be more. But if the load is not matched exactly then the intensity of this backscattered signal will be less.
So, in this way, by changing the condition of a load we can change the intensity of this backscattered signal. And if we change the condition of a load according to the data that is being stored across this RFID tag, then that data can be sent back to the RFID reader. So, in this way, the RFID reader is able to sense that data.
Now in case of a powerful coupling, as the distance between the RFID reader and tag is few is in the few meters, so the initial signal which is being sent by the reader should be strong so that the backscattered signal can be retrieved by this RFID reader. So this is how in a case of a far-field coupling, the signal is sent back to the RFID reader using this backscattered modulation technique.
Application of RFID technology
Now, let us see the different applications of this RFID technology. So, this RFID is used in a wide range of applications, and many of the applications we have already discussed. So, here the few applications in which this RFID system is used.
- Institutions: Library, hospital, schools, and colleges.
- Transportation and Logistics.
- Access Control.
- Animal Tracking.
So, I hope today you understood What is this RFID technology, how RFID technology works, and applications of RFID technology. If you have any questions or suggestions, let me know in the comments.