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.
An even bigger problem in a mobile environment is multipath, which is
far worse than the Doppler.. The effective propagation path distance
could easily change 1000 meters in a fraction of a second.
Depending on system, different approaches to handle fading and multipath
is done.
Cheers,
Magnus
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