amplitude modulation wave-type

Hi,

In amplitude modulation,the signal m(t) is modulated over the carrier to get packets .but insted why dont we simple do s(t)=Ac*cos(wt)+m(t) to get the other wave shown,all we need a high freq. carrier and this does the job.please tell me why is not used.

thank you.

Your second figure looks like a double sideband suppressed carrier, but interestingly your formula for it is a combination of frequency modulation and an additional carrier.
Frank

Hi,

In the first case, the resultng signal is not appropriate for transmission. The spectrum has a line at the carrier frequency plus the baseband spectrum of m(t).
So, if you try to transmit it by a passband channel (e.g. radio), only the carrier passes. The signal m(t) is lost.
It does not do the job.
The second fugure is not DSB-SB but standard AM.
Regards

Z

Not exactly,the percentage modulation was high.if you look closely there is still a carrier component available.

I think i get you point.

.this is the frequency spectrum.as you said,if a passband is used then m(f) is lost and using a pass band allows lesser bandwidth.

thank you.

OT: Your program looks nice and interesting. Is it free?

Thank you

Kerim

Its an online plotter, Draw Function Graphs - Plotter and its free.