Triangulate a signal

[Anders Nesheim Vinje]

I guess this is not really a electronics question but some of you guys may
know this anyway.

I was wondering how to triangulate a radio signal.
I understand that you would need three recivers at least. But how do you
measure it and get the exact position? Do you check the diffrence in time at
each reciver since it takes some time for the radio signal to travel?

Anders N.Vinje

 

[John Fields]

On Fri, 13 May 2005 23:23:45 +0200, "Anders Nesheim Vinje"
<a-vinje@frisurf.no> wrote:

I guess this is not really a electronics question but some of you guys may
know this anyway.

I was wondering how to triangulate a radio signal.
I understand that you would need three recivers at least. But how do you
measure it and get the exact position? Do you check the diffrence in time at
each reciver since it takes some time for the radio signal to travel?

---
You really only need two receivers. The receivers have directional
antennas connected to them, and the antennas are pointed at the target
so that the input signal to the receiver is maximized. Then, when
that's done, if you draw a line from each antenna in the dirction in
which it's pointing, where the lines intersect is where the target is.

--
John Fields
Professional Circuit Designer

 

[Blake]

and the antennas are pointed at the target
so that the input signal to the receiver is maximized.

Actually, because nulls in the antenna pattern are much sharper than the
lobes, you usually adjust the antenna for minimum signal. But the principal
is the same.

 

[John Fields]

On Fri, 13 May 2005 21:29:32 -0700, "Blake"
<KiwiXPlant@NoSpam.adelphia.net> wrote:

and the antennas are pointed at the target
so that the input signal to the receiver is maximized.

Actually, because nulls in the antenna pattern are much sharper than the
lobes, you usually adjust the antenna for minimum signal. But the principal
is the same.

---
Principle.

--
John Fields
Professional Circuit Designer

 

[Bob Eldred]

"Anders Nesheim Vinje" <a-vinje@frisurf.no> wrote in message
news:aT8he.9671$ai7.234277@news2.e.nsc.no...

I guess this is not really a electronics question but some of you guys may
know this anyway.

I was wondering how to triangulate a radio signal.
I understand that you would need three recivers at least. But how do you
measure it and get the exact position? Do you check the diffrence in time
at
each reciver since it takes some time for the radio signal to travel?

Anders N.Vinje

What are you trying to do? The above posters mentioned signal strength
methods to determine direction to a source. This works, sort of, it's a 20th
century method. If there is modulation on the RF carriers that can be
precicely timed, accuracy can be much greater than the direction finder
method.

Imagine two receivers, or three or even four, each with a very accurate
clock. Now imagine that there is a detectable event in the modulation like
the start of a frequency or note pattern that is detected at each receiver.
Each receiver notes the precise local arrival time of the event and from
that calculates the difference in distance to the source between it and the
other receivers. From these distances, circles of distance from each
receiver can be plotted. A vector or direction from each receiver can be
calculated from the circles and these vectors, in turn, intersect where the
transmitter is located. This can be very accurate depending on the time
resolution. Ten nanoseconds of time resolution will give an accuracy of 3
meters in location.

This is the way GPS works only there is one receiver and several satellite
transmitters but the priciple is the same. The precise timing and event
marking are in the coding of the transmitter modulation patterns and a
microprocessor does all of the required calculations and generates a
display.

A crude system working on these princilpes could work on any radio signal.
The receivers would need some electronics to establish the time base and to
detect radio modulation events. A simple readout could display the local
event time and one could manually plot the circles and vectors on a map to
determine location from these readouts. I suppose this is way beyond what
you want to do.
Bob