significance of bias block in model calculating SNR with reference to solution id 1-9T8I36 in model in the Communication blockset 4.2 (R2009a)

the block given by you in solution id 1-9T8I36 uses a Bias block which is set to -1(for measuring SNR across noise temperature block). what is the criteria to choose this value of bias and what is the basic use of the block regarding the SNR calculation? i would also like to know about the exact mechanism that you have used in developing this block? we want to use this block for measuring SNR before the the demodulator block in the demo model RF Satellite link. we have concluded that this offset has to be changed every time we change the position of the measurement. kindly reply to our request as soon as possible.

Answer 1

[Kaustubha Govind]

As far as I can tell, the input to the Bias block in the model is:

variance(noise signal)/variance(signal)

So the output of the Bias block is:

(variance(noise signal)-variance(signal))/variance(signal)

After inverting the ratio using the Math Function (reciprocal), we get:

variance(signal)/(variance(noise signal)-variance(signal))

This is the formula that the model uses ti calculate the SNR.

So a value other than '-1' for the bias does not make sense here.