Post by eestudent on Apr 20, 2006 4:47:42 GMT -5
Hi Charan
I really hope you can help clarify some confusion I have (and others to, apparently).
I am trying to make a (simple..) Link Budget for an FSK Receiver.
I need the SNR to calculate the receivers sensitivity (as Sensitivity,rx= Receiver Noise Floor + SNR).
I am able to find the Eb/N0 from the required BER (found from the waterfall curves). So now I just need to calculate the SNR according to the formula below:
(1) SNR = (Eb/No) * (R/BT) (where R=Bitrate, Bt=Bandwidth)
And this is where my problems starts; Both many books and also this application note: www.sss-mag.com/pdf/an9804.pdf claims that the Bandwidth Bt is just 2*Bitrate (for FSK).
But what if the receivers Basebandfilter is 3*times the bitrate (to have some margen to process tolerances of the filter etc) then I would imagine that the noise bandwith is increased. Is it then the Bandwidth of the Baseband filter that should be used in the formula (1) ?? Or is the calculated SNR (and the formula) completely independent of what happens inside the receiver ??
Another place I read that it was the Noise Power 'Available' to the Receiver that should be used. Then it suddently sounds like I should use the bandwidth of the SAW filter right after the Antenna ??
So which Bandwidth is the right one?
I really hope you can help clarify some confusion I have (and others to, apparently).
I am trying to make a (simple..) Link Budget for an FSK Receiver.
I need the SNR to calculate the receivers sensitivity (as Sensitivity,rx= Receiver Noise Floor + SNR).
I am able to find the Eb/N0 from the required BER (found from the waterfall curves). So now I just need to calculate the SNR according to the formula below:
(1) SNR = (Eb/No) * (R/BT) (where R=Bitrate, Bt=Bandwidth)
And this is where my problems starts; Both many books and also this application note: www.sss-mag.com/pdf/an9804.pdf claims that the Bandwidth Bt is just 2*Bitrate (for FSK).
But what if the receivers Basebandfilter is 3*times the bitrate (to have some margen to process tolerances of the filter etc) then I would imagine that the noise bandwith is increased. Is it then the Bandwidth of the Baseband filter that should be used in the formula (1) ?? Or is the calculated SNR (and the formula) completely independent of what happens inside the receiver ??
Another place I read that it was the Noise Power 'Available' to the Receiver that should be used. Then it suddently sounds like I should use the bandwidth of the SAW filter right after the Antenna ??
So which Bandwidth is the right one?
