Subject: [NEXTEL-1] Re: PROP-L:Propagation through a busy tunnel

From: Marcel <[email-masked]>
Date: Tue, 29 Oct 2002 19:49:37 -0500

------- Original Message --------
From: "Gilbert Mouget" <[email-masked]>
Subject: Re:Propagation through a busy tunnel

I think circular polarization is usefull only if the receiving antenna is 
also circularly polarized.

In the case of a simple vertical receiving antenna, two or more transmitting 
antennas evenly spaced inside the tunnel with alternating + and - 45 degree 
polarization will provide transmission diversity and avoid nulls in the
received signal.

Regards,

Gilbert Mouget

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From: Marcel <[email-masked]>
Date: Tue, 29 Oct 2002 19:50:40 -0500

-------- Original Message --------
From: Greg DesBrisay <[email-masked]>
Subject: Re: PROP-L:Propagation through a busy tunnel

Davor,

I agree with you that circular polarization ought to help because the
rotation of a circularly-polarized wave is reversed every time it's
reflected, so waves that are reflected an odd number of times are
cross-polarized at the receiver and are rejected, while wave that are
not reflected or are reflected an even number of times arrive at the
receiver with the desired polarization.  Multiple reflections tend to be
lossy as well, so the end result is that multipath is greatly reduced.

I believe Rappaport wrote a paper on the use of circular polarization to
reduce multipath in indoor environments.  The paper was probably ten
years ago or more.  I suggest you check the archives of IEEE journals
and IEEE Communications Magazine for his papers, and look around on the
web to see if Rappaport has his papers on a web site somewhere.

I hope this helps!

Greg DesBrisay
[email-masked]

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