I am trying to implement an IIR filter followed by downsampler with the following specifications:
fs=18000,order=8,3db freq=[500 1000],downsampling factor=6.
First I have designed the filter using inbuilt function ,then downsampled by a factor of 6 and gave a sine wave of frequency 700Hz as input to the filter to plot the output response. Now I have used the IIR decimator filter model to implement the system as shown in figure.Code is as shown below:
Now to convert it into fixed point representation, I have scaled the filter coefficients and then rounded out and tried to implement the difference equation .Now when I plotted the response, the system is becoming unstable