Why in radio frequency the lower the frequency the greater the transmission distance but in RFID the lower the frequency the lower the transmission distance.
*** 30 to 300 KHz – 10 centimeters**
*** 3 to 30 MHz – 10 centimeters**
*** 300 MHz to 3 GHz – 12/100 centimeters**
I’m sure there’s something I misunderstood. So could you help me to understand? please.
Hey. So RFID “antennas” are not like transmission antennas. They are inductors, and the magnetic fields they produce loop back into the coil and are never allowed to escape and become electric waves or photons. They operate only in the near field.
The RFID reader communicates with the tag when the tag enters the magnetic field and draws energy from it. In LF(125kHz) and HF(13.56MHz) lower frequency means longer range because inductors attenuate high frequencies while letting lower frequencies pass.
UHF RFID readers operate differently. They transmit electric waves, which is why they travel so far. Unfortunately that means they’re unable to transition through skin because of the dielectric properties.
Everything you know about low frequencies traveling farther in electric transmission is correct though. Those types of antennas are fundamentally different in that they toss electric waves off into space. They operate in the far field.
Even with your answer, I still haven’t understood but I guessed that you did respond me as you said (I answered your question above. why are you asking?) so I thanked you for your effort, your answer, for the time you dedicated to answer me, it is very appreciated.
Indeed, I am confused, I am not an expert or professional in this field, but I am a student trying to understand.
I am not an expert or professional in this field, but I am a student trying to understand.
So I don’t know the taste of apples neither the taste of oranges.
(Passing curiosity) but I have to understand it
For a study project, we use an Arduino card (RFID reader) and an RFID tag. For the purposes of the project everything works well.
However, I noticed that with RFID the lower the frequency the lower the transmission distance, but in general we know that the lower the frequency the greater the transmission distance that s why I asked the question.
I appreciate that you are trying to help me but I think that I find it difficult to explain my question to you given my lack of knowledge in the field.
Wavelength is the distance from peak to peak of the wave. Range is the distance at which the RFID tag can be used.
Like radio, sound has a wavelength and a frequency, but they also have an amplitude. So here is a thought experiment.
You take two people and put them on a stage. Now you stand at the back of the theatre. You get one of them to sing a low note, and the other to sing a high note at the same volume (amplitude). You can hear them both from the back of the auditorium.
Now you get one of them to whisper. You can’t hear them. Then you get the other to whisper. You still can’t hear them.
The wavelength hasn’t changed but the amplitude has and thus the range has.
The speed of a wave is calculated as the frequency multiplied by the wavelength. As the frequency drops, the wavelength increases. But the range is more to do with the amplitude.
