hi....

in my previous post i found w0 is not clear

sorry

so i'm resending my queries again.

i'm currently working on Analog Devices Dsp processor ADAU 1701..

Sigma studio is the software we are now on,in that i have some queries in

the way they calculate filter coefficient.

- main specification i needed to design a filter

1)Type[LPF,HPF, etc]

2)frequency

3)Q

4)Gain

eg:

I want a 2nd order LPF with

Frequency= 1000

Q=0.5

Gain=1

The given below derivation is the one which i got from sigma studio help

window.

->w0 = 2*pi*f0/Fs

->gainLinear = 10^(gain/20)

->Lowpass

->Transfer Function

->H(s)=1/(s^2+(s/Q)+1)

->Coefficients

->alpha = sin(w0)/(2*Q)

->a0 = 1 + alpha

->a1 = -2*cos(w0)

->a2 = 1 - alpha

->b0 = (1 - cos(w0)) * gainLinear / 2

->b1 = 1 - cos(w0) * gainLinear

->b2 = (1 - cos(w0)) * gainLinear / 2

After compiling we'll get coefficients a1,a2,b0,b1,b2 in hex format in

CAPTURE WINDOW of software.

i did manual calculation using the expression provided above and compare

with that of coeffients of software, but it differs.

Please help me to get detail calculation with the specification i given

above.

We know w0 = 2*pi*f0/Fs

-what is the value of pi(180 0r 3.14)

-w0 is the angular representation of requency i think it's 180

-then in above value of alpha will be zero always.

-it means Q doesnt have any importantce in filter design

-please suggest a good book which describe in detail about filter design

with regards

rammya