On 2/17/2011 6:22 PM, J. C. Mc Laughlin wrote:
K1TTT has nailed it! Effecting a null that is deep enough to produce
something useful is difficult. In any case, the patent examiners will
find that the telephone people did something like this a long time ago.
73, Mac N8TT
J. C. Mc Laughlin
Michigan U.S.A.
Home:
One big difference is that the hybrid in a POTS phone doesn't want a
deep null. They want enough left of what is called "side tone" to give
feedback to the ear with receiver on it. If you don't they are
uncomfortable and also think the call has been dropped. It would be in
the -10 to -30dB range I'd guess.
On the other hand the null for this antenna array would need to be maybe
90dB or better to be really useful. Maybe with processing it could be
done with less, but I'd have to say, I don't know.
tom
K0TAR