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filter = tukey_bandstop(f1,f2,f3,f4,Fs,n_points,x)
Function to generate a Tukey bandstop filter (cosine edged band stop)
----- ------
|\ /|
| \ / |
| ------ |
f1 | | |
f2 f3 f4
Inputs:
f1,f2,f3,f4
(Optional) Fs, n_points, x
These are automatically picked up when using filter_data.m
If not given then resorts to default of Fs = 100 ,
n_points =1000 (was useful for independent checking).
act 2/9/2010
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%0001 function filter = Tukey_filter(f1,f2,f3,f4,Fs,NFFT,x) 0002 0003 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 0004 % filter = tukey_bandstop(f1,f2,f3,f4,Fs,n_points,x) 0005 % 0006 % Function to generate a Tukey bandstop filter (cosine edged band stop) 0007 % 0008 % ----- ------ 0009 % |\ /| 0010 % | \ / | 0011 % | ------ | 0012 % f1 | | | 0013 % f2 f3 f4 0014 % Inputs: 0015 % f1,f2,f3,f4 0016 % (Optional) Fs, n_points, x 0017 % These are automatically picked up when using filter_data.m 0018 % If not given then resorts to default of Fs = 100 , 0019 % n_points =1000 (was useful for independent checking). 0020 % 0021 % 0022 % 0023 % act 2/9/2010 0024 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 0025 0026 if(nargin<7) 0027 Fs = 100; 0028 NFFT = 1000; 0029 x = Fs/2 * linspace(0,1,NFFT); 0030 end 0031 0032 0033 filter = ones(1,NFFT); 0034 0035 n_points = NFFT/2+1; 0036 n1 = floor(f1 * n_points / (Fs/2)); 0037 n2 = floor(f2 * n_points / (Fs/2)); 0038 n3 = floor(f3 * n_points / (Fs/2)); 0039 n4 = floor(f4 * n_points / (Fs/2)); 0040 0041 0042 %Calculate lower edge 0043 0044 for i = n1:n2 0045 range = n2-n1; 0046 j=i-n1; 0047 filter(i) = 0.5 * (1+cos((pi*j)/(range))); 0048 filter(NFFT-i+1) = 0.5 * (1+cos((pi*j)/(range))); 0049 end 0050 0051 %Calculate upper edge 0052 0053 for i = n3:n4 0054 range = n4-n3; 0055 j=i-n3; 0056 filter(i) = 1-(0.5 * (1+cos((pi*j)/(range)))); 0057 filter(NFFT-i+1) = 1-(0.5 * (1+cos((pi*j)/(range)))); 0058 end 0059 0060 %Centre region of filter 0061 0062 for i = n2+1 : n3-1 0063 filter(i)=0; 0064 filter(NFFT-i+1)=0; 0065 end 0066 0067 0068 %figure 0069 %plot(filter)