I need a good explanation of phase and magnitude spectra

[Jncik]

I understand that having a periodic signal x(t) we can find a signal y(t) which uses harmonically related exponentials in order to construct the x(t) signal

each exponential has a frequency and magnitude, for example

$$3*e^{j 2 \omega}$$ has a frequency of $$\frac{2 \pi}{2 \omega} = \frac{pi}{\omega}$$

and also a magnitude of 3

similarly $$2*e^{j 3 \omega}$$ has a frequency of $$\frac{2 \pi}{3 \omega}$$

and a magnitude of 2

now if we plot the amplitude spectra of y(t) we will get discrete values where for the x coordinate we will be having the frequency, and for the y the amplitude on that frequency

so we will have a discrete value on the frequency(x) $$\frac{\pi}{\omega}$$ with an amplitude(y) of 3 and also a value for the frequency(x) $$\frac{2 \pi}{3 \omega}$$ with an amplitude of 2

I hope that I'm correct

now, the thing is that I don't understand the phase, what will the phase represent? for example suppose we have this graph

[PLAIN]http://img191.imageshack.us/img191/8259/unledpsg.png [Broken]

what does the phase graph represent? what are these lines referring to? if you can please explain the x,y coordinates and what they mean

thanks in advance :)

 

[ehild]

The coefficients of Fourier components of a signal are complex numbers, having both magnitude and phase. So they look as Ae^jφe^jωt. The amplitude spectrum shows A(ω) and the phase spectrum is φ(ω)
If you use real Fourier series instead of complex ones, the components are of the form Asin(ωt+φ). A is the amplitude and φ is the phase of the Fourier component.

ehild