rf triangulation using phase

[Jeebus]

Hello! This is my first post and I was wondering about RF triangluation, I have read a few posts on rangefinding and such but I would like to pose a few questions.

I plan on having an fm transmitter transmitting on say 80mhz, the modulating frequency would be a physical wavelenght of say... 30meters (if anyone knows this formula, something with lambdaXfrequency and such...)

I would then have two receivers spaced apart in the room receiving and demodulating the signal leaving the modulating signal. I would then phase compare the two signals to get a compared voltage. This should give me a bearing in voltage right, by using trig?

Also I'm pretty new to this...I have seen some schematics for low power fm transmitters. I would like to have one that is crystal locked and variable to a few carrier frequencys(say 18, moved by dip switch) this way i could hold the transmitter and not affect the signal. The ones I have looked at have mics but I want to create a constant signal of 50khz(or whatever that 30m wavelenght is).

Once I get this phase compared voltage I can AtoD convert it with Arduino and throw it onto my comp right?

Any info would help thanks!

 

[akg]

I would then have two receivers spaced apart in the room receiving and demodulating the signal leaving the modulating signal. I would then phase compare the two signals to get a compared voltage. This should give me a bearing in voltage right, by using trig?

..ok..then what about the interferences from reflected and refracted signals?

 

[Jeebus]

wouldnt the receiver get the strongest signal from the shortest distance in space? like sound traveling straight to the ear? There would be refraction but the amplitudes would be lower then the straight signal...?

 

[akg]

the receiver will get a mix of all the signals..how will u distinguish between them..?

 

[Jeebus]

how does a radio distinguish a clear audio signal out of refracted radio signals?
The modulator signal is the wave length that I phase compare.

 

[Papabravo]

The frequency of an RF signal with a wavelength of 30 Meters is about 10 MHz. As I understand your description, there is no theoretical basis on which you can base your conclusions. Your efforts will be a complete waste of time.

 

[Nigel Goodwin]

how does a radio distinguish a clear audio signal out of refracted radio signals?

Generally it doesn't!, it's called 'multi-path distortion', but it's FAR more visible on TV, where it's called 'ghosting'.

 

[Jeebus]

I guess my grammer confused yall a litle.

It would be a signal carried on an fm frequency, i would demodulate and be left with the modulating one, this would be the phase i would compare

 

[Nigel Goodwin]

Bear in mind you're trying to detect VERY short time intervals, consider how far apart the two receivers are - and how long it takes light to travel that far. That's the LONGEST possible time you've got to measure, as you're considering phase comparison at the modulation frequency (presumably audio?), what percentage of the moduation frequency is the longest possible time?. I think you will find it's only a VERY tiny percentage of it.

 

[Jeebus]

Doing the phase comparison is analog right? So I will be pumping out a new phase compared signal at a certain frequency. Since the voltage will vary depending on bearing, low for right high for left. If i miss a few hundred cycles in the course of 10 msecs I will still catch one sample of the voltage every 10msecs which can be pumped into my computer. Yes I wont have data collected at 70khz but mabye 20khz or whatever my adc does.

I cant move that far in space for 10msecs to render my bearing useless.

 

[Jeebus]

By the way, thanks for the conversation.

 

[Jeebus]

for a 40 meter/single period signal I would need a 7.49 mhz modulating signal that runs on another carrier signal.

speed of light/40meters(lambda)=frequency?

it seems to work out because audio signals are wayyyy longer

 

[SamuelAaronWard]

RF Triangulation Using a PIC

Hi, Jeebus! It's been almost two years since this conversation took place, but I just now ran across it. I'm hoping that you (or someone) will see it and reply. I don't know if this website sends e-mail notifications upon replies, so could you also send your reply to samuelaaronward@gmail.com? Thanks!

I need some help. I am trying to design a little robot to go from point to point, take some kind of measurement (not important here), and log the data. I could simply tell the robot to go forward 10 feet, take a measurement, go forward another 10 feet, and repeat. But if I did that, there would be no feedback; and the robot could go off course and take measurements at the wrong positions. I was thinking about using radio frequency triangulation (or something comparable) with two known-positioned tranceiver beacons to dynamically provide negative feedback on the robots position, so that it could self-correct and stay on course. The only problem is that I am new to PICs (not that big of a problem), am fairly inexperieced when it comes to serial communication between sensors/tranceivers and microprocessors (again, not that big of a problem), and have NEVER done ANYTHING with radio frequency or triangulation (big problem)!

Okay, so a few questions...

1) Is RF Triangulation the right solution for this problem?
2) What kind of RF tranceiver do I need? Manufacturer? Model #? Cost?
3) How did you accomplish the phase compares, demodulation, and so on to figure out the robot's position?
4) Were you successful with your robot?

I am a 31 year old electrical engineer from Charleston, West Virginia, USA. In my day job, I work for an MEP (Mechanical / Electrical / Plumbing) consulting firm designing power systems for new buildings. As a hobby, I design electronics and robotics. ...If anyone out there has a solution (or any useful information) to my project, please let me know!

Thanks!

Aaron
samuelaaronward@gmail.com
(740) 357-8016 cell
(304) 343-0316 x122 office
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