# How are the original signal and the AM signal related?

Use the TIMS “Variable DC” module to generate a 1V DC signal. Use the “Adder” module to add this DC signal to the message signal generated in task 1 (this will produce the [1 + K_a m(t)] part of the AM signal). Use a “Multiplier” module to multiply this with the carrier signal c(t) generated in task 2. You will now obtain the full DSB AM signal:

Display the time-domain of this signal as well as its spectrum on LabVIEW.

Question - Compare the envelope of this signal with the original message signal, m(t) (You can display both the original signal and the AM signal on the oscilloscope to accurately compare them), how do they relate to each other?

Following picture are the result for this exercise but I am not exactly sure how to answer the question above "how do they relate to each other". Could you please explain me or give me any hint to start.

Thank you! Appreciate it!

• I guess your teacher won't appreciate it if we give you an asnwer you were supposed to find out fo yourself. But from your picture the relation seems pretty obvious to me. Could you try to explain the realtion you see in your own words? Commented Aug 27, 2015 at 11:53
• One tip: If you still can't see it, try to play with the signal vertical offset of channels 1 and 2 in the oscilloscope. Commented Aug 27, 2015 at 12:04
• @ricardomenzer the lab equipment is only accessible for class time. it is sad! thanks. Commented Aug 27, 2015 at 12:11
• @SbSangpi yeah, that's sad. But it is not so difficult to see in the picture. The keyword in the question is "envelope". Commented Aug 27, 2015 at 12:17
• @SbSangpi yes, that's over modulation, which I don't see in your waveforms. take a look at this answer: electronics.stackexchange.com/a/107144/46794 Commented Aug 27, 2015 at 13:10