Simple AM modulation Question - Thanks.

[fouadalnoor]

Hey guys, I am studying for my exam now and while reading up on my notes I got stuck at the question 2 attached.

I got my modulation factor to be 0.23 so modulation index of 23% (Vppmin = 0.25 and VppMax = 0.4)

I know the equation for amplitude modulation is:

Vam(t) = (Vc+Kam*Vm(t))cos(2*pi*fct)

I know fc = 400Hz, but how do I get the DC offset (Vc) and the modulation sensitivity Kam?

I mean, how can I sketch it etc without knowing Vm(t)?

Hope you can help!

 

[carbonzit]

Sorry, can't help. But this should be posted in the "Homework" section.

 

[fouadalnoor]

Ah thanks anyway! And I shall make sure I post it in the Homework section next time!

 

[MrAl]

Hi fouad,

Where is that first lecture the link shows?
Also, that lower case 'v' in Vam(t) = (Vc+Kam*Vm(t))cos(2vfct) is supposed to be 'pi' right? So it is:
Vam(t) = (Vc+Ka*m*Vm(t))*cos(2*pi*fc*t)
right?
You might be able to graph this if you label the Y axis as "Vc" and "Ka*Vm" or something like that to show where those appear as cos() is periodic.
Also, you are saying that the peak to peak max is 0.4 volts and peak to peak min is 0.25 volts?

Can we see that "first lecture"?

 

[fouadalnoor]

Hi fouad,

Where is that first lecture the link shows?
Also, that lower case 'v' in Vam(t) = (Vc+Kam*Vm(t))cos(2vfct) is supposed to be 'pi' right? So it is:
Vam(t) = (Vc+Ka*m*Vm(t))*cos(2*pi*fc*t)
right?
You might be able to graph this if you label the Y axis as "Vc" and "Ka*Vm" or something like that to show where those appear as cos() is periodic.
Also, you are saying that the peak to peak max is 0.4 volts and peak to peak min is 0.25 volts?

Can we see that "first lecture"?

Yeah, the little 'v' is supposed to be pi (changed it now). I have now added "lecture 1" Questions and Solutions as well as lecture 2 so we can start from there and move on.

I have solved the questions for the first lecture (questions at the end), if they are correct then lecture 2 questions just carry on from there.

PS: In the last picture in the solution's PDF (1) = NRZ (Biploar), (2) = NRZ-M and (3) = Bi-phase L (Manchester Coding)

 

[MrAl]

Hello again,

There seems to be an error in file "Lecture 2.pdf" as it wont open properly. Can you check that one and maybe upload again?
Where is your amplitude modulation solution?

 

[fouadalnoor]

Hey,

Umm it opens for me? I will upload it again just in case.

 

[fouadalnoor]

Hello again,

There seems to be an error in file "Lecture 2.pdf" as it wont open properly. Can you check that one and maybe upload again?
Where is your amplitude modulation solution?

Ok, done now. try again and tell me if it still fails to open

 

[MrAl]

Hi again,

What version of Acrobat are you using? It still wont open for me, are you sure it got replaced? Try again in another post.

 

[fouadalnoor]

Hi again,

What version of Acrobat are you using? It still wont open for me, are you sure it got replaced? Try again in another post.

I am currently using version 10.0.1 (its the most recent one)

Hmm... well I uploaded it on google docs. Just click this:

https://docs.google.com/viewer?a=v&...g4MzctNWU5YTNjMWE2NTJk&hl=en&authkey=CP-47YsF

You shouldn't need to log in or anything.

 

[fouadalnoor]

Here is L8.