why is the bandwidth of FM theoretically infinite ?

[desperado1]

fm bandwidth

why is the bandwidth of FM theoretically infinite ? can anyone explain....

 

[furqanaliali]

bandwidth in fm

actually bandlimited signals cannot be realized cuz they have infinite time duration.... and we cant generate infinite time duration signals..

So we limit the signals in time domain.. and for realizable waveform bandwidth is infinite....

now there are 4 to 5 different ways a BANDWIDTH is defined.... cuz definitely we cant take all the infinite componenets of frequency .....

i hope its clear.... i dont have right now some good link to tell u more about different definitions of bandwidth...

 

[Bhanumurthy]

bandwidth of fm

The no. of side frequencies in FM would be infinite as the modulation index increases and hence the theoritical BW of FM would be infinite.However, in practice, only significant side frequencies are considered for calculating the BW.Carson's rule gives an approximate value of BW in FM signals by taking into consideration the modulation index and freq.deviation and without the need for no. of side freq.

 

[desperado1]

bandwidth and fm modulation

is there a rule for selecting the number of sidebands in an AM signal ?

 

[Chinaski]

fm infinite sidebands

In AM there are always two sidebands. You can use carrier plus two sidebands ("normal" AM), only one sideband without carrier SSB (Upper-> USB, Lower ->LSB) or one sideband plus a reduced version of the other one (VSB->Vestigial Sideband).
There are tons of info about that, even in Wikipedia
Selecting AM, SSB or VSB depends on your application....

 

[desperado1]

what is the bandwidth of fm

Mr. Bhanumurthy.....Why is an AM called linear modulation and FM/PM called angular modulation ? Invariably non-linear elements are used in Amplitude modulation then why it is called linear ? i m a bit confused.........help me plz........

thx in advance...

 

[halls]

how to calculate fm bandwidth

Mr. Bhanumurthy.....Why is an AM called linear modulation and FM/PM called angular modulation ?

AM is an amplitude modulation, thus, it affects the amplitude of the signal being modulated. FM/PM are frequency and phase modulation, which affect the angle of the signal, so that's why these are angular modulations.

 

[Kral]

bandwidth of fm

desparado1:
See my 19 May 2009 13:46 answer to your earlier post.
Regards,
Kral

 

[amiran2001]

bandwidth + linear frequency modulation

This is because the FM spectrum consists an infinite number of frequencies spaced by modulating frequency. you can see page 192 of Carlson.