RFID Demodulation [u2270B]

[DeanM]

Hi all,

Been reading the board for a while now but this is my first post. Lot of useful information and very knowledgable people here!

My first post is seeking help! I'm working on an RFID project. It uses the u2270B basestation and a TK5551 tag for testing. The schematic is the same pretty much as application 1 in the u2270B data sheet. For the antenna i'm using these...(link below) they are 700µH coils but i use two in series for 1.4mH.
RF SOLUTIONS|ANT-125K|ANTENNA, COIL, RFID, 125KHZ | Farnell Ireland

I used a 100Ω pot for R thinking it might allow me to tune it better.

I'm getting roughly126KHz square wave output from the coil outputs. This is generating an almost sinusoidal waveform before the diode in the demod section.

PROBLEM: As mentioned, i'm getting a 126KHz waveform. after the diode i am only getting a DC voltage of about 12V. I know the RF wave should be demodulated and the input pin should show a rectified version of whats shown in the e5551 data sheet. One side of the inputcap is around 12VDC and the u2270 side of the input cap is about 2.5VDC. The cap shouldn't be passing DC. i'v changed caps a couple times and same thing is happening.

also, I seem to be getting data on the OUTPUT pin even when there is no RFID tag near the antenna.

I thought maybe the chip is damaged but its producing the output wave so i'm not certain. any thoughts? Any input would be very much appreciated. i can post schematic and PCB layout if needed.

Regards,
DeanM

 

[DeanM]

For reference...scheme & layout attachedView attachment Board.pdf

 

[DeanM]

Ok no response? well i did some further testing and it seems to be doing something. when i hold a tag to the coil the output on pin2 of u2270B changes. But even without a tag there is output present. Should there be? I thought the out put would be nothing unless there's a tag present?

 

[abukede]

Hi.

Im also beating with the head to demodulate a tag with the same U2270B... but in my case I now for sure that the reader is working fine.
When I read the I/O of the u2270b with a LA I also get surprised with the same... see this print screen with no tag



and with tag:



As you can see you have nothing in the INPUT pin but you have random data on the pin OUT. the only data that you have in the INPUT is a copy of the data that you put in the CFE

By the way if you any clue about what I ask help in my post please don't hesitate to answer https://www.edaboard.com/threads/220100/