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Author Topic: How to design and make pcb antenna?  (Read 30145 times)
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Ichan
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« on: June 30, 2013, 08:20:10 20:20 »

I am interested in designing and producing pcb antenna for 13.56 MHz rfid tag and reader, need some clue...

What software? Antenna Magus looks promising but i can not find any newer version on the web.

How about the production process? Substrate choice, copper plating tolerance, solder mask effect, etc etc.

I believe many expert about this thing in here  Wink

And if someone have this book please..

-ichan
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h0nk
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« Reply #1 on: June 30, 2013, 10:05:34 22:05 »


Not exact the topic, but...

Some time ago i have made RFID antennas from RG-58 cable placed in a polycarbonat housing.
Think of it as a VERY BIG mousepad.
The housing was commercial made with CNC machinery.

The design for the antennaelement followed the TI application notes (Loop with a gamma match when i do correctly remember).

With the help of an impedance bridge (Palstar ZM-30) i did a prototype with simple wires to get a good impedance match.
This experimental design was used to made the final antenna.

Perhaps You should try it the same way to get an idea of the geometry.
Since 13.56 MHz are mostly magnetic antennas, FR-4 should do no harm to Your design.

I have also tested a printed yagi design for UHF-RFID, but thats not that easy as 13,56 MHz :-)


Best Regards
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Parmin
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« Reply #2 on: July 01, 2013, 01:21:03 01:21 »

I think there is a topic in Texas Instruments App notes that deal with this.
I have a book somewhere on this too, but been a while since I read it, I can't even remember the title.
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optikon
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« Reply #3 on: July 01, 2013, 01:32:03 01:32 »

I am interested in designing and producing pcb antenna for 13.56 MHz rfid tag and reader, need some clue...

What software? Antenna Magus looks promising but i can not find any newer version on the web.

How about the production process? Substrate choice, copper plating tolerance, solder mask effect, etc etc.

I believe many expert about this thing in here  Wink

And if someone have this book please..

-ichan

at ~13 MHz, Fr-4 isnt too lossy, so you are ok with standard material.

I think there is some free antenna design software that ham guys use. I dont know it but i recall seeing it. you have to search

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solutions
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« Reply #4 on: July 01, 2013, 02:55:04 02:55 »

http://www.antenna-theory.com/definitions/nfc-antenna.php
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Ichan
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« Reply #5 on: July 01, 2013, 07:15:22 19:15 »

Thank's to all comments.

As suggested, I just spent about 2 hours browsing about this, many docs found are too complicated to me - i can't chew much math equations anymore  Cheesy.

One which is still readable for me is from ST website as attached.

Next question, how if the coil is on both side of the pcb? As picture below.

Thank you.

- ichan.
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mexpcb
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« Reply #6 on: July 01, 2013, 07:25:37 19:25 »

you can simulate in hfss or CST...

here is an example with transponder...

http://www.cst.com/Content/Applications/Article/RFID+Transponder+operating+at+13.56+MHz

for material you can use FR4 and the plating can be Gold Plating or Silver Plating, but if you are going to use a home made version, you can ass some small resin to prevent oxidation, that's what mainly the plating is for...
and about the material i personally think that on this case it will be just a support for the active circuit which is the inductive antenna and you can set it up to face with the receiver from the copper exposed side of the board. you can imagine the dielectric material as small piece of water when you make a beam of light pass through and will see some reflections and refraction, thats what it going to happens with the EM Fields , the ones going out from the copper area of PCB will be more uniform and the ones going out from the bottom side will be different, what it's important to consider here is that the surface will be a planar surface, if you see on the pdf, it's an conductor and as you may know to have a better field coupling for the Magnetic Field, those will pass through air, then for the FR4 material and again to the Air because magnetic fields always end in a closed loop.. and i never simulated this but i think it will be better to use a pure wires (with out Dielectric material mechanical support)  with the same pattern shown on the pdf because a pure wire is a cylindrical shape and because the E Files are perpendicular to the conductor surface, you will have a better radiation pattern...





if you want to create a fancy circuit you can try to make the PCB on a glass material like what ti was done here.

http://hackaday.com/2011/09/12/glass-pcbs/

https://www.youtube.com/watch?v=5ZH1-eScY0M

i hope this helps..
regards


{EDIT}in your post you mention "Design", if you want to make a Design, you need to go and use math Smiley

here is some papers of the math involve..

http://ww1.microchip.com/downloads/en/appnotes/00710c.pdf
http://ww1.microchip.com/downloads/en/devicedoc/21299e.pdf

and here is a video of Altium of how to draft on the PCB..
https://www.youtube.com/watch?v=qPpYDlLpjyk

Regards
« Last Edit: July 01, 2013, 07:37:32 19:37 by mexpcb » Logged
Ichan
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« Reply #7 on: July 01, 2013, 08:27:09 20:27 »

Thanks a lot for the explanation.

Well, looks like i have to try one of that big software - will those software do "design" antenna?

My target will be similar to the last pcb tag picture, that tag size approximately (by comparing to the chip size which is 5x8mm) is about 15x30mm - rather small to build a coil with enough inductance for 13.56MHz i guess so they make it in two layer coil. Does it mean the coil on that tag is forming a "n turn 2 layer square coil" (for calculation)?

Speak straightly, what i curently need is a design of a round pcb antenna for 13.56 Mhz Mifare chip (MOA4 package) with diameter smaller than 35mm - i will be very grateful if any expert in here to give it a try..  Cool. The choice of pcb can be 0.3mm FR4, 2 layer, ENIG plated, soldermasked on both sides, the chip preferably located at the center of pcb.

That Net Ties on Altium is something new to me, thanks.

-ichan



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h0nk
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« Reply #8 on: July 01, 2013, 10:06:11 22:06 »

TI had made several Evaluationboards for there RFID Chips.

http://www.ti.com/general/docs/lit/getliterature.tsp?literatureNumber=sloc133&fileType=zip

In the documentation You will find the Layout which include a PCB antenna, Gerber files and the
Schematics.

AN710 from Microchip is also a good source of information.

Perhaps this helps.


Best Regards
« Last Edit: July 01, 2013, 10:13:52 22:13 by h0nk » Logged
TucoRamirez
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« Reply #9 on: July 02, 2013, 09:17:35 09:17 »

what about that 125khz pcb antenna Huh 
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« Reply #10 on: July 02, 2013, 01:55:41 13:55 »

Tuco - got schematics, or at least the ID of those two chips on there?
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« Reply #11 on: July 02, 2013, 02:32:38 14:32 »

sorry solutions ^^  i dont know the sch but its a EM4095  and a pic , they are following the sch of the datasheet as long as i know:

http://www.emmicroelectronic.com/webfiles/product/rfid/ds/EM4095_DS.pdf
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Ichan
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« Reply #12 on: July 05, 2013, 04:17:37 16:17 »

Easier to find information for Reader antenna, but not for Tag antenna.

I may try to rev-eng some antenna and let the expert here analyzed it using HFSS or CST (?)

-ichan
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« Reply #13 on: July 06, 2013, 12:20:08 00:20 »

Going down tuco's rabbit hole, there's a bit of reader antenna design info here: www.emmicroelectronic.com/webfiles/product/rfid/an/an404.pdf‎
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PeterMcMonty
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« Reply #14 on: July 14, 2013, 09:25:59 21:25 »

Maybe the two files attached here could be useful in finding formulae to calculate planar spiral inductances, as RFID antennas are.

An on-line calculator, based on the pdf article, can be found here:
http://smirc.stanford.edu/noCSS/spiralCalc.html

PeterMcMonty
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« Reply #15 on: July 15, 2013, 12:23:51 00:23 »

Going down tuco's rabbit hole, there's a bit of reader antenna design info here: www.emmicroelectronic.com/webfiles/product/rfid/an/an404.pdf‎

Damn it i'm stucked on that hole for  125khz .... Sad
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« Reply #16 on: July 15, 2013, 05:47:09 17:47 »

Maybe the two files attached here could be useful in finding formulae to calculate planar spiral inductances, as RFID antennas are.

An on-line calculator, based on the pdf article, can be found here:
http://smirc.stanford.edu/noCSS/spiralCalc.html

PeterMcMonty

How much inductance required for 13.56 Mhz? How is the required matching network? Picture on reply #5 use only 1 cap for it (?)

-ichan
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« Reply #17 on: July 20, 2013, 12:09:23 12:09 »

Hi

Mouser site have low cost antenna for 13.56MHz (below 1 $)
Whether you need only few - it is possibly worth it

All the best

Bobi
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Ichan
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« Reply #18 on: July 20, 2013, 04:47:30 16:47 »

Thanks, i need the antenna as part of the whole circuit, on the same pcb - going to chase a project with a massive quantity..

-ichan
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« Reply #19 on: July 20, 2013, 08:04:10 20:04 »

How much inductance required for 13.56 Mhz? How is the required matching network? Picture on reply #5 use only 1 cap for it (?)

-ichan

As explained in the pdf application note by ST you posted on reply #5, the coil antenna toghether with the resonant capacitor forms a parallel resonant LC circuit whose resonant frequency is given by:

f0 = 1 / (2π SQRT(LC))

so you have to choose C and then determine L for f0 = 13.56 MHz.

C comprises parasitic capacitances too.
« Last Edit: July 21, 2013, 12:28:01 00:28 by PeterMcMonty » Logged

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« Reply #20 on: July 21, 2013, 09:52:24 09:52 »

The inductance of my antenna was around 1 uH.
This may be a good starting point.
With approx 140 pF (120 pF capacitor + 30 pF trimmer capacitor) it was easy to adjust the resonant frequency.
A 10 k resistor parallel to the capacitor was used to increase the bandwidth of the antenna.

For the matching network You may find the tool RFSIM99 useful.
G..gle should find it.

Be aware that available chips may have a very low impedance.
The TRF7960 for instance around 4 Ohm.

You should also not underestimate the influence of materials in the neighbour of Your antenna.

Without some measurements all simulations are rather useless.


Best Regards
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