antenna-theory.com

[wolberine]

I was perusing some RF vendors and came across a pretty interesting antenna:

http://www.spectrummicrowave.com/antennas_wifi_pro_dual_band.asp

Can anyone shed some light as to what type of radiator it is and how it might work?

[bigSteve]

It's tough to tell from the picture. My guess:

I assume the light colored region is copper, and the dark region is something like FR4. This could be backwards though. Assuming this is correct:

The top T-shaped line is the feed, which is an aperture coupled feed. The second layer (the light colored rectangle with the U-shape cut out) is a patch antenna, with a slot cut in, which tends to increase bandwidth. Then I believe there is a bottom ground plane layer below it.

[wolberine]

What physical characteristics make this a 2.4GHz/5.8GHz dual-band antenna?

From this site, it looks like the aperture coupled feed can be used as a capacitor to tune out some unwanted inductance on the feed leg.

[bigSteve]

The half-wavelength at 2.4 GHz determines roughly the size of the antenna. Bringing in 5.8 GHz is pretty easy, it is not quite the 3rd harmonic but can be brought in with matching or by messing with the feed and slot.

[wolberine]

so this seems pretty straight forward as long as you have a network analyzer and an anechoic chamber:

1) make a 2.4GHz patch, play with the feed to capacitively change the impedance of the antenna

2) rely on the 3rd harmonic being resonant also to make the 5.8GHz patch

3) play with the patch slot and maybe a matching component to optimize bandwidth and match at 2.4GHz/5.8GHz