1. 
   Frequency shift
   In the physical sciences and in telecommunication, the term frequency shift has the following meanings: ...
   Found op http://en.wikipedia.org/wiki/Frequency_shift
   
   
2. 
   frequency shift
   an intentional frequency change produced by modulation, or an unintentional change due to a natural phenomenon
   Found op http://www.electropedia.org/iev/iev.nsf/display?openform&ievref=702-01-12
   
   
3. 
   frequency shift
   in angle modulation by a discretely timed signal, the difference between the frequencies corresponding to two signal elements of the modulated signal, assuming steady state conditions
   Found op http://www.electropedia.org/iev/iev.nsf/display?openform&ievref=702-06-46
   
   

Tip: double click on a word to show its meaning.