Using radio frequencies to loosely determine angles

Hi,
I'm curently working on a project that I had an idea for. I'm a highschool student and pretty new when it comes to radio frequency projects, so bear with me if I'm not too precise. What I'm trying to do is have a robot that would be able to determine at aproximately at what angle it is at relative to a transmiter. What I was thinking of doing is having a parabolic reflector around the receiver antena (made of a conductive meterial), in which the receiver would be be located at the focus. When the signal would be coming head on, the signal strenght would be at it's highest. When it is at a angle, some of the signal would be reflected off of the parabola and the signal would lose energy. So what I'm thinking is that the signal strenght would be inversaly proportional to the angle at which the transmiter is to the parabola. So if I could mesure the signal strenght, I could find at what angle the transmiter is with the receiver. So my questions are, what hardware do you think I would need. I'm thinking of doing this on a Uno, but any suggestions on what antenas, ect I would need? The receiver can be pretty big, but the transmitter would have to be kind of small. Also, have you ever seen any similar project. If you have, it would be really useful to provide a link. And finally, is it even feasible or am I just crazy.

It's not likely to work because of reflections and side-lobes.

Google "Arduino Radar" and see if that gives you any ideas.

I think discussing this with some Ham radio operators will work out better for you. Antenna angles, diameters, frequency are all interdependent.

Just a suggestion look up triangulation, it is used worldwide for location, including GPS and RADAR. If you calculate the angles from two known transmitters you can determine one of two points. With three you know where you are and altitude could be calculated if given enough information. On the amature radio side look up foxhunt, that is exactly what they do on a bigger scale. With these solutions your robot does not need to power the transmitters.

It’s not that complicated. What you’re suggesting is single receiver direction finding. Google it.

Or, use GPS and you'd know everything you could possibly want with respect to position.

sachafusco-myles:
And finally, is it even feasible or am I just crazy.

Feasible, but not in the way you think.

The signal strength will vary with distance, so from a given signal strength you cannot know if you are close at one angle or far away at another.

However if you can rotate the antenna you can adjust the rotation for maximum signal, then you are pointing at the transmitter.

As has been suggested, look up stuff for 'Amateur Radio Fox Hunt'

Reflections will be an issue but other than that… sure, should kinda work, and having a nicely designed antenna spinning around on top of the robot will definitely look cool!

Something you need to understand is wavelength A direction finding antenna needs to be comparable to the wavelength of the particular frequency, generally at least half the wavelength. How big will your robot be?

Use local am radio station as a Tx, for receiver use regular AM radio with modified antenna, shield is making ferrite antenna more directional with sharp nil.

mag-ant.gif

mag-ant.gif

Look up. VOR

It is how pilots know the angle they are from the airport

You can do the Line Of Position thing. Like in Loran-C and Omega, as noted above basically RDF.

3 or 4 transmitters covering the field from different angles would create a LOP grid on the field which can then be used for navigation. Similar to WAAS (Wide Area Augmentation System) being used with GPS to get greater location accuracies.

Even better is if you can receive WAAS on the field signals just use that system for the transmitters.

VOR requires a transmitter sending a varying signal that is received by avionics in the plane and is processed to display as a number from 0 to 359. Not very useful for a hobbyist at home where transmitters send out the same signal in all 360 degreees.

I’ve also seen some people who ground the parabolic shield. Would that be necessary, and if so, how would I do that?

sachafusco-myles:
I’ve also seen some people who ground the parabolic shield. Would that be necessary, and if so, how would I do that?

Are you thinking of a parabolic REFLECTOR? A shield means NO signal can be received. Perhaps something in the 70gHz range that is used in automobile RADAR would work. The reflector/antenna are quite small.
Paul

Paul_KD7HB:
Perhaps something in the 70gHz range that is used in automobile RADAR would work. The reflector/antenna are quite small.

And that is what I was pointing out. How good are you at 70 gHz technology?

Update on your thinking. You wrote: "So if I could mesure the signal strenght, I could find at what angle the transmiter is with the receiver.". The reality the ONLY angle you might determine is exactly ZERO, which would be when you found maximum received signal strength. If you found other maximums, then your antenna design is defective.
Paul

Paul__B:
And that is what I was pointing out. How good are you at 70 gHz technology?

Well, I have never worked with 70 ghz. To be honest, my experience with radio frequency’s is what we learn with high school physics in Canada and me tinkering with RFID over 125khz. But I do get that I’m going to need to consider wavelengths. Obviously it probably wouldn’t work in the kilohertz range because of the big wavelength. But I’m thinking the width of the reflector would be around 30cm. So I did some fast math and it would probably have to run at least at a few megahertz. Also for the purposes of the project, it can’t be ridiculously expensive or extremely hard to program. And also, sorry for wrong vocabulary I meant reflector when I said shield. So would I need to ground the thing and how would I do that if necessary.

Paul_KD7HB:
Update on your thinking. You wrote: "So if I could mesure the signal strenght, I could find at what angle the transmiter is with the receiver.". The reality the ONLY angle you might determine is exactly ZERO, which would be when you found maximum received signal strength. If you found other maximums, then your antenna design is defective.
Paul

Yeah, what I meant to say is that the receiver with the reflector would be rotating until they could find the maximum strength and pinpoint in what direction the signal is coming from. I know that you can’t mesure the actual angle because the strength would vary with distance. However, I just want to know if it could determine direction and what kind of antenna would I have to order.

The “directional antenna” technique works with any radio frequency, but wire antennas get very large for low frequencies.

A multielement dipole antenna is fine for handheld use at 100 MHz and above. The more elements, the more directional and sensitive the antenna. Examples used for manual bird tracking can be seen here: Manual Radio | Advanced Telemetry Systems.

For low frequency AM, the ferrite loop antenna works well, as it is very small and directional. Find a working AM pocket-sized transistor radio to verify this for yourself, and see how the station volume varies as you point the radio in different directions. (Keep in mind that all consumer radios have “automatic volume control” that tends to hide the effect).

I have a little robot vacuum cleaner which can run about my house randomly, and always finds its way back to its dock. When it goes into docking mode, I notice that it will stop moving, and rotate back and forth around its initial heading. It may do this repeatedly as it gets closer to the dock. I am sure it has a directional antenna in it which gives it a rough idea, by the varying signal strength, of which way to alter course. By successive approximations, as it gets closer, it can refine its estimate.

Putting three very directional antennas in your robot, oriented by enough angle to have a significant directional effect, you could read the strongest one, turn toward it, and continue doing the same approximation as you got closer.

Good luck. It’s a pretty good challenge.