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I have bought four RF sensors from Robokits - Wireless RF serial link 433 MHz +20 dBm 2 Km range.

I want to locate one of them with the help other three sensors by the means of triangulation. My project requires this localisation under distance of 2 meters. So, how can I reduce the range of these sensors to 2 m?

I'm using Arduino, Raspberry Pi as processors for the project. Any documentation/reference links would also be welcome. I have worked on ZigBees before but this is the first time with RF.

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    \$\begingroup\$ What accuracy/resolution do you need for your project, I'm willing to bet that 1) there is a minimum distance that the RF sensors can detect. 2) the resolution is something in the 10cm to 1m range. Detection is based off of time of flight, even if you did succeed in reducing the range, the resolution would not change. \$\endgroup\$
    – Voltage Spike ♦
    Commented May 17, 2019 at 20:17
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    \$\begingroup\$ Different frequencies, but the exact same problem. What you want to doesn't work like that. \$\endgroup\$
    – Marcus Müller
    Commented May 17, 2019 at 20:51
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    \$\begingroup\$ and for a 1.5m resolution, you'd need a timing resolution of 1.5 m / c = 1.5 m / (3·10⁸ m/s) = 5 ns, i.e. a receiver bandwidth of 200 MHz. You can't triangulate a narrower signal (like yours) to such a resolution – physics doesn't allow it. \$\endgroup\$
    – Marcus Müller
    Commented May 17, 2019 at 20:53
  • \$\begingroup\$ You're welcome to join the line of other people who, like you, want to use some of-the-shelf RF modules (Bluetooth, 434 MHz or whatever) to do triangulation. I have yet to see someone do this successfully (but please prove me wrong!). The reason for that is as Marcus mentions above, the laws of nature doesn't allow this. \$\endgroup\$
    – Bimpelrekkie
    Commented May 17, 2019 at 21:13
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    \$\begingroup\$ @Bimpelrekkie we can do magical things by abusing a lot of statistics and using high-resolution SDRs. Just not like OP. You'll be astonished what one can with RTL-SDRs and LoRa and lotsa brains. \$\endgroup\$
    – Marcus Müller
    Commented May 17, 2019 at 21:33

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It is not practical to use these cheap radios for triangulation.

Although you can display you can Mux the Tx’s and read the data signal strength with 1dB resolution, due to reflections and standing waves you will be able to detection motion but not distance with a resolution of maybe 25% change in distance even if calibrated in an anechoic chamber or open field. The antenna power can be reduced by replacing it with a short vertical stub to get down below -60dBm. Group delay and TOA in each radio will not likely be the same for the resolution you want.

Orientation , Reflections and Rice Fading will cause much more error than you expect.

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