# Angle Modulation!

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#### Wond3rboy

##### Member
hello everyone, i have a presentation coming up on this monday which requires me to expalain FM and also explain the figure attched.Since it is hard to make it out i am going to give two lines about it:

The upper one is the comparasion of FM and PM with the Modulation voltage(x-axis) and the Frequency or Phase Deviation(y-axis).

The lower one is the comparasion of FM and PM with the Modulation Frequency(x-axis) and the Frequency or Phase Deviation(y-axis).

I can do the FM part but can any one explain or atleast help me in this regard

PS:I am using Communication Systems by Simon Haykin and Telecommunication Techniques by Warren Hioki.

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#### microtexan

##### New Member
Angle Modulation

Angel Modulation?

#### Hero999

##### Banned
I've always spelt it angle, angel must be a US variant which is wrong as we invented the English language.

EDIT:
Isn't an angel like a fairy?

I can't spell because I'm dyslexic.

Aren't phase modulation are the same thing?

Last edited:

##### Well-Known Member
The essence of the lower graph is that the relationship between modulation frequency and frequency deviation is very different when you use a PM modulator vs when you use an FM modulator. When FM modulating, the frequency deviation remains constant no matter what modulating frequency is used. However, when using a phase modulator, the frequency deviation increases with modulation frequency. This lower graph therefore shows that the FM modulator differs from the PM modulator by a mathematical differentiation (or conversely integration). Which one? Depends on your point of view. If you want an FM modulator, you can add an integrator before the PM modulator. If you want a PM modulation, you can add a differentiator before the FM modulator. (now, did I get that right, or is that backwards? I often confuse myself on this).

#### Nigel Goodwin

##### Super Moderator
I've always spelt it angle, angel must be a US variant which is wrong as we invented the English language.
I suspect it was simply a spelling mistake?.

EDIT:
Isn't an angel like a fairy?
Sort of, it's a mythical creature from heaven, satan was a fallen angel.

#### Wond3rboy

##### Member
you can add a differentiator before the FM modulator. (now, did I get that right, or is that backwards? I often confuse myself on this)

you got it right and i now that but i dont thihnk that will count as an explanation in front of the class thats why was looking for some other insight?

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