[time-nuts] GPS first LO need to be locked?
attila at kinali.ch
Fri Mar 31 07:35:03 EDT 2017
On Thu, 30 Mar 2017 20:00:31 -0700
Peter Monta <pmonta at gmail.com> wrote:
> > BTW a lot of GPS receivers don't have a "first LO".. they are more like a
> >> Tuned RF receiver - an input BPF for L1, L2, or L5, then direct sampling at
> >> around 30-40 MHz - something that makes the GPS signals alias down
> >> somewhere convenient (and always have positive frequency offset from zero,
> >> even at max negative Doppler)
> True. I've been wanting to try this with an FPGA transceiver; even the
> cheap ones go to 6 Gb/s now, but binary only. The newest transceivers
> support PAM-4, which would be great, but they're not affordable yet. Also
> that's a lot of gain at one frequency.
I guess you know of  already?
Alternatively, instead of using a MAX2021, you can use a discrete
mixer and use the high analog bandwidth of todays ADCs to use them
as downmixers.  and  describe how to do this in detail.
The epitome of this is using direct sampling of the signals without
previous downmixing (e.g. ). Though I have no idea how easy or hard that
is with todays electronics. It will definitely need good preselection
filters to keep SNR high.
 "A Prototyping Platform for Multi-Frequency GNSS Receivers",
by Akos, Ene and Thor, 2003
 "Design of a GPS and Galileo Multi-Frequency Front-End",
by Parada, Chastellain, Botteron, Tawk, Farine, 2009
 "Design and Implementation of a Direct Digitization GPS Receiver Front End",
by Akos, and Tsui, 1996
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson
More information about the time-nuts