passive tag schematic

Is there HF RFID tag chips integrated with MCU and/or did someone tried to emulate the RFID tag using mcu ?

There was a very old An from Microchip about using a PIC12 (powered from magnetic field) to emulate a RFID card.

have not seen it on microchip site . Do you have copy
to upload ?

I have to search it on a old CD from Microch..
Anyway, they only provide connection scheme nothing else.
It's a full wave rectifier with 4 diodes: on a diagonale is connected the antenna, in the other diagonale 2 pins of the PIC.

Ok , if it is only schematic case , no upload isneeded as content is obvious . Bytheway , I have found Atmel's chip for transponder with integrated 4bits mcu , but for LF band . So may be similar tags do exist for HF band as well .

I don't think you can emulate the RFID tag using an MCU. When you design the antenna, its output (which should be 50 ohm) has to be matched to the input of the MUC. I think you should buy the IC specially made for it.