[AR] Re: SDR Radio's was "infrastructure" (was Re: Amateur solid rockets for ...)
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Mon, 18 Dec 2017 16:34:52 -0500 (EST)
On Mon, 18 Dec 2017, Robert Steinke wrote:
If you have a fixed array of omni antennas, and you know what direction your
signal is coming from you should be able to work out the time lags and phase
shifts that the various antennas would see.
Could you "track" in software by filtering the signals from the omni
anrtennas with those time lags and phase shifts, and any signal from that
direction will constructively interfere?
Yes, in principle, although the implementation can get complicated. It's
called a phased-array antenna.
If you want to do all the combining in software, that means you need a
separate receiver for each antenna. It is usually considered preferable
to have a controllable phase shifter behind each antenna and combine the
signals electronically immediately after that, so they can go into a
single receiver, but some systems do postpone the combining. (One reason
for doing so is that you can then do the combining in multiple different
ways to receive from several sources simultaneously.)
There are limits to this -- in particular, the farther off the centerline
you try to "point the beam", the broader and sloppier the beam, and hence
the poorer the receive performance.
Henry
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