The RFID chip absorbs RF power from the RFID reader through the antenna. The RF power rectified by the rectifier and power up the core of the RFID chip. Then, the chip transmits the information through the antenna?
Since the RFID reader is transmitting the RF power, the RFID chip antenna will excited by the RF power. How the chip receives the RF power and transmits the information at the same time? How it avoids the collision of input RF power and output information in the antenna?
Any recommended book that describes the detail of RFID chip?
Many thanks
Passive rfid chips work by shorting or opening their own antenna which changes the amount of power they draw from the reader antenna, for near-field rfid, or the amount of power that is reflected back for far-field rfid. The reader can detect this variable load or small reflected signal.
Read application notes that are available on the internet, such as this one
http://ww1.microchip.com/downloads/en/appnotes/00710c.pdf
The wirelessly activation of the chip is due to the unmodulated signal sent by the RFID reader and received by the tag antenna and routed to the RFID chip, the RFID chip rectifier and an internal voltage doubler transform the week signal into direct current (dc) and doubled it into a sufficient high (dc) to charge the capacitor, which allow a short operation periods even without the presence of the carrier wave, now the tag is activated and ready to receive commands from the reader. The tag replies to the amplitude shift keying (ASK) sent from the reader by backscattering. After the RFID chip is activated it change it impedance between absorbing and reflecting state depending on the contained data in its internal memory
this book can be very helpful
**The RF in RFID. UHF RFID in Practice by Daniel M. Dobkin**
Dear Ll Lee ,
The RFID rf wireless transceiver works in a half duplex mode. such that the transmit and the receive sessions occupy different time slots.
The reader transmit strong rf signal to activate the TAG and then the tag can receive and transmit the signal from the reader.
There is no collision at all because of the time division multiplexing of the different sessions.
Best wishes
Hopefully, this article will be helpful and fruitful to your research.
"A Compact and Flexible UHF RFID Tag Antenna for Massive IoT Devices in 5G System"
If you know about Time Division Multiplexing or FDM or OTDM then the answer becomes simpler. These multiplexing techniques are used but instead of one way communication, dual way communication is implemented and the send receive timing is clicked on devices using protocols.
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