antenna-theory.com

[KV124]

Hi All,

Hum, everyone want to make an antenna that works as well as it can, I want to make an antenna that works well in proximity and poorly at distance. I am trying to build a WiFi hot spot that can be a dominant hot spot, but only when the other device is placed in close proximity to my antenna.

Think tablet computer being placed within a shallow tray. When in position my hot spot drowns out other nearby hot spots and forces the device to reconnect and registers with my hot spot, data is then transferred, then when they pick up the device, my hot spot fades quickly in quality while their normal hot spot returns to its clear signal status so their device re-registers and life goes on.

I'm thinking something kinda like NFC, but with WiFi. I'm thinking 1) turn down my power level (be just strong enough to drown out other hot spots when device is in place), and use a screwed up antenna that mostly radiates upward so devices off to the side can't see me very well, and almost no gain, so I don't interfere with floors above me...

In other words a piss-poor or at least a mis-applied antenna design

Any good ideas as to which direction I should head?

Thanks so much for your ideas,

Keith

[wolberine]

I think one of the issues with the problem is antennas are symmetrical: if they're good transmitters, then they're good receivers. If you want to reduce the range on the antenna in general, you could always make it less efficient. If you want to reduce the range of the antenna in a given direction, you could look into directional antennas.

You mentioned the tablet computer entering a tray - you'd like a good Wifi signal within the tray and a bad Wifi signal when the tablet is removed from the tray. If this is a one-off design, I'd suggest locating your Wifi antenna in the tablet (search your tablet's FCC ID on fcc.org for a tear down for antenna placements). Then, you could always try to capacitively (or maybe inductively) couple to the tablet's Wifi antenna with some hacked antenna design. Get creative. If the Wifi antenna is an inverted F, maybe you could closely couple with a loop near the inductive arm. I don't know if that works, but experiment around.

Good luck!