Magnus Danielson wrote:
On 09/30/2010 06:14 AM, jimlux wrote:
Magnus Danielson wrote:
Doppler effects is much more important, and it's effects is being
treated regularly, such as when talking in the GSM phone while driving
the car...
Hmm.. I think crystal oscillator frequency variation in the phone is a
bigger factor. Let's say you're zipping down the road at 200 km/hr
(55m/s), texting your friends. That's about 0.2ppm Doppler or around 400
Hz (for a 2 GHz carrier).. as noted.. the XO probably has 1ppm (at
best.. more like 10ppm)
On why there is a big market for small but stable TCXOs at 26 MHz.
how stable? I'm sort of curious, I wonder what sort of temperature
range cellphones are expected to really work over.. (not necessarily
what they're specified for, but what the designers see as the "sweet
spot").. It's not like people carry their phones in pocket on the back
of a backpack in -40 weather.
I wonder if they're like pager receivers in some sense (e.g. they're on
all the time, waiting for a call)
And, as the phone heats up as you transmit, how much does the frequency
change?
It's a real cost sensitive huge volume market, so the specs for a
cellphone reference oscillator could be highly tailored to a specific
application.
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