PCB Antenna

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#1
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Does anybody know a good article about the calculation and the design of PCB integrated antennas?

Kind regards!

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Microchip has an application note (AN831) called "Matching Small Loop Antennas to rfPIC™ Devices" that might help. Google for "microchip" and "an831" and it should take you right to the app note.

Dave

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What frequency? How large is your circuit board?

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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Nordic had some design notes for their chips IIRC.

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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There basically is no one simple answer.

If it is "low frequency" (say under 500KHz), a multi=turn "coil" on the circuit board is probably "best". When it it UHF (300MHz and higher) then rully resonant radiators or patches. In between, its a mixed bag, sometimes loops, sometimes dipoles, etc. I don't know of any general guide that covers all frequencies. If you can describe your application and frequency, more help can be offered.

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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Quote:
I don't know of any general guide that covers all frequencies.
A metal coat hanger works at all frequencies :lol:

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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The ones you have seen were imported from NZ :D

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I've seen a design for an antenna for the 2m amateur band that was made from straightened out wire coat hangers.

Leon

Leon Heller G1HSM

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A simple 1/4 wave antenna will have an impedance of about 50 ohms. That's how many PCB antennas are made.

Leon

Leon Heller G1HSM

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Thanks for your replies.

Well, i had no internet access the last days, therefore the late reply.

Well, basically i want to lear how how to design a printed circuit board integrated antenna for the frequency of 125 kHZ.

As you might presage, i would like to build an experimantal RFID Reader device.

I have already read the appnotes from EMMicroelectronics and some other vendors, however i most of the times found very special details for antenna tuning, which might be only true for a very specific chip.

For now, i just want to learn the basic calculations for integrated PCB antennas in general, not only in reference to RFID...

Thanks!

Kind regards,
Franz

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125 kHz is a very low frequency for a PCB antenna, they are usually used at much higher frequencies like 2.4 GHz. A ferrite rod antenna would be better.

Leon

Leon Heller G1HSM

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125Khz RFID isn't really an antenna, it's more of a transformer construction. Usually a series LC circuit tuned to resonate at 125Khz. L is usually 700uH with a capacitor where you've to take L's parasitic capacitance in account.

You want a relatively high Q for maximum range (that means low wire resistance), but the higher the Q the less tolerance there is for transponders that are a tad off-tune. So there's a trade off here.

I made a few coils in the past; with a scope you can tune the coil for maximum amplitude (which can be several hunderds volts 8)) by adding or removing turns.