Harmonic

[zesla]

Hi,

I have a question regarding AM Modulation,
As you know a square wave has just Odd harmonics. I want to know what will happen reagrding harmonics if
we amplitude modulate a signal with a square wave carrier (at say 40Mhz)? Say the modulating signal is 1MHz too.

Thanks.

 

[BrownOut]

If memory serves me, the resultant spectrum of the signal will look like the original, but shifted along the positive and negative frequency axis, and each positive and negative "copy" will be 1/2 the original amplitute.

 

[crutschow]

You will have odd harmonics of 1MHz spaced at plus and minus intervals centered at 40HMz.

 

[MikeMl]

I'm assuming you want to modulate a 40MHz sine wave carrier with a 1MHz square wave. Here is what LTSpice shows:

First plot is time-domain (zoomed in)
Second plot is FFT of 100 cycles of above.
Third plot is FFT zoomed near 40Mhz.