2.4 GHz patch antenna for RFID

[abhishek.vnit]

Patch antenna for RFID

Hi to all,
I am presently designing an antenna for 2.45 GHz .. I need to design antenna having as small size as possible and as high gain as possible..
I will be using a microstrip patch antenna. For 2.4 GHz, Half wavelength is apprx. 125 mm .. Is it necessary that patch dimensions have to be approx. equal to this value???
I have seen some examples where various patch shapes were designed to have reduction in size.. (Techniques such as folding)... This made me wonder what about the RFIDs which are being used.. If they used antenna with lengths (dimensions) of 5 cm!!!! I also came to conclusion that the dielectric permittivity must be kept high (~10) to reduce size... My aim is to investigate if a patch antenna array of very small length (around 1 cm) could be used to harness the ambient RF power.
It would be of great help if anyone of you could point to papers where design of small antennas for 2.4 GHz is given.I would like to have a patch antenna of dimensions less than 1 cm which works for 2.4 GHz.. i do understand that using a high dielectric would introduce impedance matching problems, but I could do with a high feed point impedance. Could you clarify on this???
Thanking you.
Abhishek.

 

[BrunoK]

Re: Patch antenna for RFID

Hi there
What polarization should the antenna have? I have design i microstrip antenna for 2.4 GHz whic was circular polirazed. I read several articles, I remember that some of them just investigated this topic ( smaller size) the most widely used folding as you have mentioned. I will try to find during this weekend. But as far as I remember some of the other antenna parameters got worse. As you in a way have mentioned, the substrate of use affects the size. Whic dielectric constant are uyou using?

Best Regards
Bruno

 

[rautio]

Re: Patch antenna for RFID

A high dielectric constant that results in a smaller dipole means most of the energy is constrained to the dielectric, this reduces radiation. You are up against a fundamental trade-off...smaller antenna means less radiation.

 

[biff44]

Re: Patch antenna for RFID

I have used this dielectrically loaded ANT-916-JJBRA antenna at 900 MHz. It worked fine. You should be able to find or design a similar one at 2.4 GHz. It is some super high dielectric puck over the end of the wire, reducing the length considerably.



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