[time-nuts] antennas was Re: Common-View GPS Network

[Jim Lux]

On 4/18/13 1:40 PM, bg at lysator.liu.se wrote:

> All of the "high quality" GNSS receiver manufacturers have their own
> version  of correlator that try to mitigate multipath. See for example
> this Ashtech-document (for a ca 10 year old L1 only receiver (DG14/16)).
>
>   ftp://ftp.ashtech.com/OEM,%20Sensor%20&%20ADU/DG16%20&%20DG14/Reference%20Material/Correlator.doc
>
I'm sure..

I wonder, though, if you have a GPS receiver for which you do not know 
how it works internally, can one come up with a guideline for how much 
multipath suppression you want.

At some level, all those fancy algorithms are trying to build an 
adaptive equalizer and/or filter for the multipath, helped by the 
knowledge that the "true" path is the shortest one.

In theory, one should be able to deconvolve arbitrary multipath (if you 
collect all signals from all directions of the sky, etc.), but I think 
the idea of the chokering (and other clever antenna designs) is to 
reduce the work for the back end processing.