Multisim and Ultiboard

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fourier analysis resolution and length settings

I'm trying to simulate DSB AM in multisim with VBM voltage source

so I have

 

Vu=Vm*Vc

 

I can't seem to get the Fourier Analysis to display correctly.  The graph only display up to four times the fundalmental frequency Smiley Sad.  My carrier is at 1Mhz and my message is at 10Khz all sine waves.  So ideally, I should get three peaks: 0.99Mhz, 1Mhz and 1.01Mhz.

 

Is it possible to use configure the fourier analysis so that I can see these peaks?

Please help.

 

See attached for schematic.

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Anyone???

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Hi,

 

I am using the Network Analyzer to simulate your circuit the result shows two bands, one at 990 kHz and another 1.01MHz.  From the following trigonometric indentities:  sin(x)*sin(y) = 1/2 {cos(x-y) -cos(x+y)}, and it looks like the Multisim simulation is correct it.

network.PNG

 

 

I looked up AM modulation from the following page:

http://www.pa2old.nl/files/am_fundamentals.pdf

It  looks like the express is:

Capture.PNG

 

There is an AM source avalable in the Multisim database, it's located in "Sources" group under the "Signal Voltage source".

 

Tien P.

National Instruments
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