[time-nuts] Last Call Group Buy Ublox LEA-6T

Attila Kinali attila at kinali.ch
Thu May 19 13:17:17 EDT 2016


On Thu, 19 May 2016 09:08:40 -0400
Bert Kehren via time-nuts <time-nuts at febo.com> wrote:

> Today GPS receivers are getting better by the year due to the fact that in  
> order to save silicon the chips are getting smaller and the clock frequency 
> goes  up reducing saw tooth excursion. If it was not for hanging bridge 
> filtering it  on the input of a GPSDO would be simple without info from the 
> receiver

This assumptions do not hold true. GPS timing receivers are almost always
just standard receivers with special firmware and slightly modified hardware.
The normal GPS receivers are optimized for low power consumption as they
are integrated into mobile devices. As such, the clock frequency with which
the baseband processor runs will hardly change, as the frequency is the
biggest knob with which the power consumption can be tuned. 

The node size of microcontrollers is also kind of stuck, mostly due
to power consumption constraints. If you want a transistor to switch
off well and not just becomming a high valued resistor, you have to make
it big. Hence most microcontrollers have a process node size between 130nm
and 250nm. Few use 90nm (i'm only aware of the high end STM32 uC). Low power
microcontrollers can even use larger node sizes (350nm and larger).

You can see this phenomena with the LEA modules quite clearly: 
The LEA-4, -5, -6, -7 and -8 modules all use an internal 48MHz clock. 
Even though there were 2 complete overhauls of the system in this ~13 year
timespan.

				Attila Kinali
-- 
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


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