CR95HF EMI Filter for Pulse W7001 antenna

[Tom Gensi]

Posted on September 09, 2017 at 10:44

Hello,

I have a lot of CR95HF for a project that could read NFC Tags of a medical equipment and send this via bluetooth to a smartwatch.

I works but i would have now the Pulse W7001 NFC antenna on the CR95HF Chip and we can't get a running system with this antenna.

we did not get good results with the calculation tool on the site from the CR95HF chip.

Could anyone help with this antenna on the CR95HF Chip?

Antenna

https://www.arrow.com/en/products/w7001/pulse-electronics-corporation

CR95HF

http://www.st.com/en/nfc/cr95hf.html

Thank you very much

Best regards from Germany

Tom

[Petr Ourednik_O]

Posted on July 11, 2018 at 17:05

Hi,

did you tried the ST eDesign Suite for NFC antennas to study basic principles please?

It is available on

http://my.st.com

P.

[Petr Ourednik_O]

Posted on July 12, 2018 at 16:14

Hi,

as I checked your design and ext. vendor antenna I am expecting the matching issues.

The maximum power transfer between the CR95HF and the load is obtained when the

condition Z

out

= Z

load

is obtained.

Z

load

is the complex conjugate of Z

load

.

The antenna equivalent impedance an

inductive antenna

does not meet this condition.

The measure of Z

load 

gives: Zload = (0.6 + j . 36.6)Ω

To achieve the maximum power transfer between the CR95HF and its inductive antenna,

impedance matching must therefore be performed between Z

out

and Z

load

. It allows to:

�?

Optimize the read range

�?

Transmit the maximum power

�?

Optimize the chip consumption

�?

Maximize the radiated magnetic field

Please read the

AN3394

Application note for

Antenna design and impedance matching guidelines

for CR95HF multiprotocol contactless transceiver IC here:

https://www.st.com/content/ccc/resource/technical/document/application_note/33/ae/18/cb/dd/0f/46/96/DM00027198.pdf/files/DM00027198.pdf/jcr:content/translations/en.DM00027198.pdf

... in order to check the matching of your design.

best regards,

PO

[drmaxoude]

Hi,

I'm using the same schematic as Tom.

I tried to to use the Application Note AN3394 in order to make the matching circuit but without any success to read a tag. My configuration is working fine with a custom antenna made with wound wires but it's not viable.

Is anybody there who find a solution ?

MG