bandwidth of AM signal

[fran1942]

Hello, if I was using an 800Mhz carrier which was modulated with the range of frequencies 200Hz-3.3khz, what would be the total bandwidth ?

Would it be 3.1Khz * 2 = 6.2kHz or would it be 6.6kHz ?

Thanks for any help.

 

[iVenky]

It would be 6.6Khz

 

[jtrent]

Your bandwidth is determined by the highest frequency that you use. In your case it is 3.3KHz. So your bandwidth would be 2 times your highest frequency. 2 * 3.3KHz = 6.6KHz

 

[iVenky]

I think what you are confusing with is bandpass sampling. It's quite different.

 

[kemiyun]

There are some schemes for reducing the bandwidth requirement for signals on a band. If it is important to save bandwidth for your application use that kind of modulation. So in short you might get 6.2 kHz with some modification.

The modulator should be something like this (I am not sure):
-First mix your signal with carrier frequency.
-High pass filter it at your carrier frequency.
-Mix the result with carrier frequency plus your upper frequency.
-Low pass filter it at carrier frequency or what the spectrum requires.
There may be mistakes in this scheme. Haven't calculated or looked at the spectrum. But it should be something like this.

 

[jtrent]

Yes, Kemiyun, of course the bandwidth can be reduced by filtering. I think fran1942 was asking about AM Modulation without any consideration given to modifying his signals.

 

[kemiyun]

Oh I thought it was something in general. My bad, sorry. But I believe it is worth analyzing amplitude modulation as convolution on frequency domain. This analysis makes me feel much more comfortable and I am no expert but I would suggest this way to determine bandwidth of any signal.