Basic communications

Discussion in 'Wireless & RF Design' started by raks_universe, Jun 2, 2010.

1. raks_universe Thread Starter Active Member

Mar 15, 2009
67
0
Hi..

Why the signal is viewed as in-phase and quadrature phase component,,,??

what is necessity to view the signal as this,.,.,???

In my books,.,this procedure is also followed for modulation techniques too....

Pls help me,.,.,

Thanks...

2. stephen163 New Member

Nov 12, 2009
5
1
It turns out that you can send two digital bit streams at once by modulating the carrier wave with one these bit streams and the same carrier wave shifted by 90 degrees by the other bit stream. These are just cosine and sine waves at the carrier frequency. The two are added together and transmitted. The resulting signal is made up of an in-phase component (i.e., the bit stream modulated by the cosine wave) and the quadrature component (the bit stream modulated by the sine wave).

I would look up QAM, QPSK and generally what quadrature mixing is. This will lead to constellation diagrams as a way of visualising the in-phase and quadrature component of a signal.

pursefocus likes this.
3. raks_universe Thread Starter Active Member

Mar 15, 2009
67
0
Hi friend ,.,.thanks 4 ur reply,.,.

I am very very beginner to communication concept...

Can u pls explain in easier way.....

In linear modulation scheme,why we r using in-phase and quadrature phase component for representing a signal.,.,.(as follows)

s(t) = sI(t)cos(2πfct) - sQ(t)sin(2πfct)

what is the necessity to view the signal s(t) in this manner,.,.,???

pls help me....

4. raks_universe Thread Starter Active Member

Mar 15, 2009
67
0
s(t) = sI(t)cos(2πfct) - sQ(t)sin(2πfct)

How this equation is formed ???