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I'm thinking about a device that can communicate with a phone. Think of it as simply something that will tell an app "1" if it communicates with it, otherwise the app will remain "0."

But what I want is for it to, for example, be able to be placed on a table, and it facing a certain way. If two people are sitting opposite each other on the table and the device is pointing towards one of them, it will tell the person it is pointing towards "1" but the other person, who is "outside of the cone" would not get a "1" because of that and his app would stay at "0." The person it is facing towards could move to the side a few feet and no longer receive a "1" because he moved out of the "cone."

I know there are directional antennae, but that seems to be more about increasing the signal strength.

Specifically it would only need to cover a few square feet.

I guess bluetooth is really the way you would communicate with an iphone/android. Is this possible to work with bluetooth?

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  • \$\begingroup\$ I know that there are a lot of obstacles, but can you do this acoustically? Use the built-in mic & speaker? Problems abound: the mic placement on different phones is different, speaker placement is different. Some phones have two mics to determine directionality - might that be usable? \$\endgroup\$
    – Dwayne Reid
    Feb 28, 2015 at 5:21
  • \$\begingroup\$ If this really is as simple as a true/false, with no other information passed, either wifi or bluetooth would work fine. The app need only scan the list of devices/networks. I feel wifi would be better for this case, since the SSID of interest would be broadcast continuously. \$\endgroup\$
    – user39962
    Feb 28, 2015 at 7:39

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Directional antennae are used to obtain directionality as well as increase signal strength. Just like a flashlight concentrates the beam from a light bulb into a smaller area, a directional antenna increases signal strength as it narrows the coverage area.

Bluetooth should be ideal because smartphones already have it, the frequency is high enough to make a compact directional antenna, and range is short so it should be less affected by signals from outside the 'cone'. To minimize stray signal pickup you should use the lowest transmitting power that can still be received inside the distance you want to cover.

Your antenna doesn't need to be very efficient, so its dimensions are not particularly critical. You can make one out of an old tin can, a metal box open at one end, or a curved plate acting as a reflector.

How To Build A Tin Can Waveguide WiFi Antenna

Home made WLAN 802.11 Antennas

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