Reply-To: "fred bartoli"
From: "fred bartoli"
Subject: Re: Radio Direction Finding
Date: Wed, 6 Nov 2002 11:02:07 +0100
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NNTP-Posting-Date: 06 Nov 2002 10:59:29 MET
Keith Wootten a écrit dans le message :
> In message <firstname.lastname@example.org>, Frank
> Raffaeli writes
> >It would help to understand why you have this constraint.
> >How much smaller?
> Handheld, pocketable, rugged. Has to work over ~30 metres with
> licensable power. I don't want to use a voltage probe primarily for
> aesthetic reasons and also because of their sensitivity to interference.
> I suspect it's not feasible, otherwise I would've found some reference
> by now, but it's always worth running these things past others.
> >Without more details on your application, it's hard to develop a good
> >design assumption; however, I suggest you look at TDOA (time delay of
> >arrival) and doppler methods. A TDOA system can work very well with
> >antennas smaller than 1/4 electrical wavelength, at the expense of
> >efficiency. A TDOA system can be implemented by switching two antennae
> >/ RF amplifiers at the reciever, and using the output of the receiver
> >phase detector to adjust a servo that dynamically adjusts antenna
> >position. There is no ambiguity but the drawback is that the antennae
> >rotate via servo. For a stationary, but slightly more complicated
> >solution, use the doppler.
> Thanks, I'll have a look at TDOA, although my size constraints would
> make the time difference (thus phase) rather small.
At 40MHz, a 1° phase difference is only 2cm. One degree should be fairly
easy to resolve.
> Keith Wootten