where is the ground reference in rfid tags(NFC) ?
I'd like to ask what is actually gnd reference for RFID Passive tag (such as 13.56MHz NFC) ?
because there is no connection to the PCB or any physical ground, how to define the ground for the reference of the internal circuits ?
Do the tags need a very solid reference ground for the internal circuit design ?
Thanks in advance
Regards,
Lisong
From what I have observed, RFID tags generally contain dipole like antennas. And, as in a dipole, you have two balanced elements and no separate ground.
RFID tags at UHF frequencies are using antennas (like dipole)
At 13.56MHz RFID is using inductors.
The tags don't have a ground reference. The IC only has two connections to the inductor. It contains a rectifier and one output of the rectifier is used as internal 0V.
thanks for your answers.
the differential signals obtained by the inductor go into the rectifier, but I saw most of literatures about the rectifiers have a solid ground, and regarding to this, the differential ac signals are converted to single end DC signals by this kind rectifier.
What my doubt is right here that there is no solid ground in the tags, and then how to work of the rectifer ?
sorry for the fresh questions.
Lisong
Why do you think there's a need for a "solid" ground? The chip substrate can be considered as a ground, and the internal signals can be best described referencing to it. But it has no meaning for the outside world.
thanks for your replies. Regarding to it , the function of ground is to sink current ,and should be very low impedance. I really can't imagine how the internal circuit works due to no this kind gnd connection.
1. all currents are circulating inside the chip
2. low impedance referred to the other circuit nodes inside the chip
If you have a basic circuit with a battery and a light you also have no ground.
The current flows through the circuit, and that is the same as in every other device.
You need a closed circuit paths, the line that is often used is called "ground".