delta-sigma toolbox

clear;clc %% Designing a decimation filter. % We start by desinging a decimation filter in double precision. The % decimation filter is a low pass filter with a decimation rate of 64. The % filter specification is from the AD1877 Anolog Devices Sigma-Delta % data sheet. You can find the data sheet at % http://www.analog.com/UploadedFiles/Data_Sheets/AD1877.pdf % The desing of the filter takes about 10 seconds. As such, for a faster % start up the design is stored in a file. If you need to redesign the % filter, simply uncomment the lines below and run the script. Decimation_Factor=64; Passband_Ripple=.006; %dB Stopband_Attenuation=90; %dB Fs=48e3; Passband=21.6e3; %dB Stopband=26.4e3; %dB Input_Sampling_Rate = Decimation_Factor*Fs; f=fdesign.decimator(Decimation_Factor,'lowpass',Passband,Stopband,... Passband_Ripple,Stopband_Attenuation,Input_Sampling_Rate); h=design(f); save one_stage h fvtool(h,'Fs',Input_Sampling_Rate); %% To have a more efficnet implementation, we break down the filter into hm=design(f,'multistage','Nstages',3); save multi_stage hm fvtool(h,'Fs',Input_Sampling_Rate); %% We then convert the filter into fixed-point. hf=hm; hf.stage(1).Arithmetic = 'fixed'; hf.stage(1).CoeffWordLength = 24; hf.stage(1).InputWordLength = 2; hf.stage(1).InputFracLength = 0; specifyall(hf.stage(1)); hf.stage(1).OutputWordLength = 12; hf.stage(1).OutputFracLength = 10; hf.stage(1).ProductWordLength = 8; hf.stage(1).ProductFracLength = 10; hf.stage(1).AccumWordLength = 13; hf.stage(1).AccumFracLength = 10; hf.stage(1).RoundMode = 'nearest'; hf.stage(2).Arithmetic = 'fixed'; hf.stage(2).CoeffWordLength = 24; hf.stage(2).InputWordLength = 13; hf.stage(2).InputFracLength = 10; specifyall(hf.stage(2)); hf.stage(2).OutputWordLength = 13; hf.stage(2).OutputFracLength = 10; hf.stage(2).ProductWordLength = 10; hf.stage(2).ProductFracLength = 10; hf.stage(2).AccumWordLength = 13; hf.stage(2).AccumFracLength = 10; hf.stage(2).RoundMode = 'nearest'; hf.stage(3).Arithmetic = 'fixed'; hf.stage(3).CoeffWordLength = 24; hf.stage(3).InputWordLength = 13; hf.stage(3).InputFracLength = 10; specifyall(hf.stage(3)); hf.stage(3).ProductWordLength = 11; hf.stage(3).ProductFracLength = 12; hf.stage(3).AccumWordLength = 14; hf.stage(3).AccumFracLength = 12; hf.stage(3).OutputWordLength = 16; hf.stage(3).OutputFracLength = 15; hf.stage(3).RoundMode = 'nearest'; hf.stage(3).OverflowMode = 'saturate'; save multi_stage_fixed hf fvtool(hf,'Fs',Input_Sampling_Rate);