[time-nuts] GPS simulator,
Luis Cupido
cupido at mail.ua.pt
Fri Nov 26 16:02:29 UTC 2010
> But they mention software to generate sequences.
Hummm... right...
so I think we need to look inside one to be sure what it is...
lc
ct1dmk.
jimlux wrote:
> Luis Cupido wrote:
>> Hi,
>>
>> The fact they refer that atmospheric s/n degradation and dropouts etc
>> being replayed precisely lead me to think this is just a spectrum
>> rec/play machine (no mod/demod of any kind)
>> like the ham-oriented "time machine" but for GPS.
>> http://www.expandedspectrumsystems.com/prod2.html
>>
>> Luis Cupido.
>> ct1dmk.
>>
>
>
> But they mention software to generate sequences. It's actually a fairly
> clever idea. It's easy to stream 16.3xx Mbps from a modern computer, so
> you could generate an arbitarily complex signal off line..
>
>
> For a lot of applications this would be great. A nice test source that
> you could replay on command.
>
> The only question I'd have is whether the 1 bit DAC can adequately
> represent the real-life complex signal. I suppose, intuitively, since
> your receiver is digitizing it with a 1 bit ADC...
>
> And, I have a question whether the 1 bit DAC can produce a high enough
> fidelity waveform for a higher performance receiver that uses a multibit
> digitizer.
>
> Since the clock you are recording and playing back with isn't
> necessarily as good as the one on the satellite, you probably couldn't
> use this for testing your precision receiver. It would be like
> introducing a random propagation variation or coax length variation in
> the system.
>
> It is intriguing though.. a homebrew version could be quite simple.. you
> can get the USB interface and a small FPGA pretty easily. One of those
> 10.23 MHz crystals from Rick might be handy...
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
More information about the time-nuts
mailing list