I met an great confusion.
Using below command I have got co-efficents for a 300Hx cut-off high pass filter of order two.
[z p k] = butter(2,(300/44100),'high') [sos,g] = zp2sos(z,p,k)
Now this sos co-efficients are differ from what is obtained by fdatool.
As explained here https://dsp.stackexchange.com/a/19553/7868 , what i am wondering is why even for a 2nd order filter the co-efficients are different obtained by both methods.