Why always Envelope detector in Passive RFID Tags?
I have read some papers regarding the passive tag design. I see the envelope detector to demodulate the signal from the reader.
Can anyone let me know why it is always envelope detector? Why do we see only amplitude changes?
-shaikss
Tags use ultra low power to maximize reading range. Envelope detection is low power, even better, it is the way to harvast power for the tag to operate.
Tags must also be low cost, so small die area.
The envelope detector provides an output which is the "envelope" of the input RF signal.
That means can detect only the amplitude modulated signals, kind of modulation which most of the RFID use.
The envelope detector is appropriate for the modulation methods used with 13.56 MHz (and also LF) RFID. Which other demodulator types do you have in mind?
The envelope detector is appropriate for the modulation methods used with 13.56 MHz (and also LF) RFID. Which other demodulator types do you have in mind?
There are other demodulaltors like FSK/BPSK etc. But clarified why ASK is alone used.
Yes, but they aren't compatible with the basic operation of a passive tag. I already mentioned it in another of your threads, but apparently you didn't yet get the implications.
It's the simple fact, that the RFID tag doesn't have an independent clock available, it uses the carrrier frequency itself as a clock. So it's basically unable to "see" carrier phase or frequency changes.
Yes, but they aren't compatible with the basic operation of a passive tag. I already mentioned it in another of your threads, but apparently you didn't yet get the implications.
It's the simple fact, that the RFID tag doesn't have an independent clock available, it uses the carrrier frequency itself as a clock. So it's basically unable to "see" carrier phase or frequency changes.
Thanks FvM. I understood the content from your earlier post only.