Hello all,
Can somebody please explain how to calculate a receiver IF Filer bandwidth ?
I've looked through the internet and found two ways...I can't tell which one is the right one.
For example:
Transmitter parameters are:
Data rate: 500bps
Peak deviation: 250Hz
Modulation index = 1
Modulation method is 2-Level GFSK
One way of calculating the above is:
Carson's rule: BW=2(peak deviation + max modulation frequency)
The maximum modulation frequency is 250Hz = 500bps (assuming that a 500bps square wave fed into a bt=0.5 gaussian filter results a 250Hz sine wave)
BW is = 2(250 + 250) = 1KHz
The other way is using bessel chart:
If the modulation index equal 1, so there is 3 sidebands (according to the chart)
BW= 2* (max modulation frequency) * (number of sidebands)
BW= 2 * 250 * 3 = 1.5KHz (which is 0.5KHz wider then carson's rule calculation)
Which is correct?
Thank you,
Nir
