RFID Antenna Design - Is This Possible? 1

• Jul 29, 2015

• #2

VEBill

Military

Apr 25, 2002

7,090

CA

There are various forms of slot antennas. Because you start with a conductive surface and then cut slots into it, they end up perfectly flush with the surface. Obviously the gap would need reinforcement on the back side with a dielectric material.

RFID tags come in a range of frequency bands. What band is involved here?

 

Upvote 0 Downvote

• Jul 30, 2015

• Thread starter
• #3

40HrCaptain

Electrical

Jul 27, 2015

4

US

Currently torn between HF 13.56mhz and LF 125khz. The reader will be battery powered so energy consumption is very important to me. It also seems that LF performs better in heavy metal environments, which this device will operate in.

Any approximate idea how deep the slots would need to be so that the antenna sits flush with the cylinder face? Or how much of a gap would be required between the cylinder face and the antenna?

Also - how far could I wrap the antenna around the cylinder? Would 180, 270, or even 359 degrees cause issues? The idea here being an antenna that could read a tag from any orientation around the cylinder face.

 

Upvote 0 Downvote

• Jul 30, 2015

• #4

VEBill

Military

Apr 25, 2002

7,090

CA

Neither 13.56 MHz nor 125 kHz "antennas" (of the usual design theories) will fit into the space you've indicated.

If it only needs to span a cm, then perhaps a simple half-transformer multi-turn loop might work. Depending on the reader transmitter, you might need to provide a matching circuit.

 

Upvote 0 Downvote

• Jul 30, 2015

• Thread starter
• #5

40HrCaptain

Electrical

Jul 27, 2015

4

US

I see...Why wouldn't they fit? How much space is needed?

 

Upvote 0 Downvote

• Jul 30, 2015

• #6

VEBill

Military

Apr 25, 2002

7,090

CA

For example, a dipole antenna for 13.56 MHz is about 34 feet in length. There are many techniques to shorten antennas, but for this application it seems best to just abandon the concept of an antenna as such, and just feed a multiturn loop.

Obviously 125 kHz is even moreso.

 

Upvote 0 Downvote

• Aug 7, 2015

1
• #7

khiggler

Electrical

Apr 17, 2014

15

US

RFiD antennas are very specialized antennas and normal antenna size dipole requirements don't work. RFiD antennas are closer to wound transformers than they are dipole antennas.
I suggest you attempt to buy RFiD antennas and evaluate how well they work. You need to have a system spec for what will work.
A normal antenna would be a slot with coax across it, and the slot and internal cylinder would be filled with high dielectric and probably lossy potting or MAGRAM, which usually is high dielectric, potting compound and low loss at your frequencies.
Kevin

 

Upvote 0 Downvote