What makes quadrature mixing possible?

Den s�ndag den 31. august 2014 19.17.17 UTC+2 skrev miladsp:
> so I've been reading quadrature signals, quadrature mixing and hilbert
> 
> transform and while most of it makes sense I find quadrature mixing a bit
> 
> confusing. What I can't get my head around is the fact that we can transmit
> 
> in-phase and quadrature parts of the signal on the same physical channel.
> 
> What are exploiting here? Am I right in thinking that we're essentially
> 
> transmitting a complex signal using a real signal? 
> 
> How did we implement the j-operator? Are we exploiting the fact that sin
> 
> and cos carriers are orthogonal? If we had another pair of orthogonal
> 
> signals that didn't look like sin or cos at all, could we use them to do
> 
> the same thing and modulate two independent I and Q signals on one physical
> 
> channel? Do sin and cos have any significance?
> 
> 

https://www.youtube.com/watch?v=h_7d-m1ehoY
https://www.youtube.com/watch?v=5GGD99Qi1PA

-Lasse