RFID reader for handheld antenna

[Roger Hebert]

Posted on January 12, 2018 at 14:44

#Hi everybody,  

I try to connect only the antenna (on a handheld device with a spiral cable) on a CR95HF (inside a control unit). Can you let me know how to calculate the circuit parts with this additional parameter?   In the application note (attached file)   

Thank you for your help.  

Roger.

[Peter Boringer]

Posted on January 15, 2018 at 11:11

Hello Roger,

Can you provide more informations, please, about the antenna circuit (L, C, Z) you are using how and where you try to connect it to the CR95HF and the characteristics of the cable used to make this.

Regards

[Roger Hebert]

Posted on January 15, 2018 at 15:19

Thank you very much for your reply Pierre-Yves,

We are manufacturer of control systems for beer, soda and liquor for bar and restaurant. We have a project for a liquor control that will use RFID technology. Each bottle of alcohol will have its RFID tag (inside a spout) that we will have to read with a reader. The entire reader will be in the control unit except the antenna which will be part of an activator (including a solenoid) which will be connected to a spiral cable.

We want to use the same circuit that is part of your application note # AN3 For the needs of our test, we made a circular antenna with an impedance of 0.70 µh that we connected directly to the reader circuit. Everything worked very well. We are at the stage of doing the tests with the activator. Our antenna will have a value between 3.83 µh and 4.01 µh when measured alone. When we connect it to the spiral cable the measured value at the end of the wire is 6.31µh (with an antenna of 3.83 µf).

The spiral cable will be a 6 conductors, 60 '' long when extended.

Let me know if you need more information’s,

Thank you very much for your help.

Cheers.

Roger Hébert,

B.V.L. Controls Ltd.

661, de la Sablière

Bois-des-Filion (Québec) Canada

J6Z 4T2

Tel. [phone]

Fax [phone]

<http://www.bvlcontrols.com> www.bvlcontrols.com

________________

Attachments :

image001.gif : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006HyC2&d=%2Fa%2F0X0000000b4R%2F14G7Nc7l6ZM9neEwIyZQPrb4RVuOO55NT2jadVwPrvs&asPdf=false

Demo Circuit.jpg : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006Hy4O&d=%2Fa%2F0X0000000b4S%2FG1PqqwA15azv1EYKCQhozfz0lrXhyNa6b9Lc63JFtmE&asPdf=false

en.DM00027198.pdf : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006HyBs&d=%2Fa%2F0X0000000b4Q%2FboRdbyxFLx_lDIWlHwYrQ0jjJQoaAH7v70.aniVNqpY&asPdf=false

IMG_8236A.jpg : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006HyBF&d=%2Fa%2F0X0000000b4P%2F.eOohZQRmMatRvJ9pvX5OzFwpsA33ipauo4bolcDcrE&asPdf=false

activator.png : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006Hxv7&d=%2Fa%2F0X0000000b4G%2FG3AGUN3tdveAHjTiAJ7RnGDWANBr0bFCsbbnbxXJ83Q&asPdf=false

[Peter Boringer]

Posted on January 22, 2018 at 11:46

Hi Roger,

Thank for the clarification.

What I can tell with your proposal is that the antenna matching calculation will not work if the system: antenna + cable +  antenna matching is higher than 4uH.

So it will be preferable to reduce at least the total impedance and thus reduce the antenna alone impedance between 1 and 2uH.

Based on the parameters provided above you should have a total impedance matching the 3/4 uH expected value.

Last take care about your spiral cable the behaviour can vary in case this cable is short or fully extended.

Do you have already experiment it?

Sincerely yours

PYB

[Roger Hebert]

Posted on January 22, 2018 at 14:52

Hi Pierre-Yves,

Thank you very much for you answer.

Yes, we have tried an antenna of 0.80µh for a total of 3.33µh with the cable and it does not work. Do you have anything else we could try?

Thank you very much for your help.

Cheers.

Roger Hébert,

B.V.L. Controls Ltd.

661, de la Sablière

Bois-des-Filion (Québec) Canada

J6Z 4T2

Tel. [phone]

Fax [phone]

<http://www.bvlcontrols.com> www.bvlcontrols.com

________________

Attachments :

image001.gif : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006Hy2j&d=%2Fa%2F0X0000000b4A%2FobuRZxUJjx8maQGJC9kKIhCzVQt.u7BVzKwAViL3LII&asPdf=false

[Peter Boringer]

Posted on January 22, 2018 at 17:19

Hello Roger,

Can you please tell me if you have recompute the antenna matching circuitry because by modifiying the antenna characteristics you will have to adjust the tuning circuitry.

This can be done using the CR95HF EMI FILTER CALCULATION.xlsm spreadsheet.

Tell me if it is fitting your needs

Thanks and regards

PYB