# Describe a measurement method for estimating the frequency deviation for frequency modulated signals

#### ekram1234

Joined Aug 6, 2020
3
Hello,

Can anyone please answer this question: Describe a measurement method for estimating the frequency deviation for frequency-modulated signals.

Any response would be highly appreciated. Thanks

#### Deleted member 115935

Joined Dec 31, 1969
0
If you can tell us what level of answer you need for this home work, are you a university or school ?

What sort of frequency you looks at, MHz, GHz ? what amount of deviation from centre frequency you expecting , MHz, HZ, GHZ , and how fast are you expecting the frequency to vary ?

#### WBahn

Joined Mar 31, 2012
27,946
MOD NOTE: Moved to Homework Help.

#### MrAl

Joined Jun 17, 2014
9,640
Hello,

Can anyone please answer this question: Describe a measurement method for estimating the frequency deviation for frequency-modulated signals.

Any response would be highly appreciated. Thanks
Hi,

I had this very same question several decades ago The only difference is mine was more like, "How do you demodulate an FM signal".

Demodulating FM is more complicated than demodulating AM, but there are some simple ways that are probably only good for making measurements, but it also depends on what kind of measuring devices you have. For example, an oscilloscope.

#### ekram1234

Joined Aug 6, 2020
3
If you can tell us what level of answer you need for this home work, are you a university or school ?

What sort of frequency you looks at, MHz, GHz ? what amount of deviation from centre frequency you expecting , MHz, HZ, GHZ , and how fast are you expecting the frequency to vary ?
I am studying at a university and this is one of the questions from a sample exam question paper.

#### ZCochran98

Joined Jul 24, 2018
221
Look up Carson's Rule for frequency modulation. If you have a spectrum analyzer you can get most of the information required to approximate the frequency deviation (which is different from the demodulated signal). Keep in mind that FM bandwidth is a little tricky sometimes, and the spacing between peaks in the sidebands is relatively constant (for simple sinusoidal signals, anyway) and equal to the highest frequency in the modulating signal.

#### Delta Prime

Joined Nov 15, 2019
1,311
Hello there the question was very ambiguous so the answer is correct and also ambiguous phase-lock loop #### ekram1234

Joined Aug 6, 2020
3
Hello there the question was very ambiguous so the answer is correct and also ambiguous phase-lock loop where is the answer that you are referring to?

#### Delta Prime

Joined Nov 15, 2019
1,311
We
Describe a measurement method for estimating the frequency deviation for frequency-modulated signals.
Frequency modulation index is defined as the ratio of maximum frequency deviation of the carrier signal to the frequency of the message signal. I'm skating on thin ice here trying.... to help you!go with it .good luck . 