| Signal Processing Toolbox | |
Raised cosine FIR filter design
Syntax
b=firrcos(n,F0,df,fs)b = firrcos(n,F0,df,fs,'bandwidth')b=firrcos(n,F0,df) b=firrcos(n,F0,r,fs,'rolloff') b=firrcos(...,'type') b=firrcos(...,'type',delay) b=firrcos(...,'type',delay,window) [b,a]=firrcos(...)
Description
b = firrcos(n,F0,df,fs)
or, equivalently,
b = firrcos(n,F0,df,fs,'bandwidth')
n lowpass linear-phase FIR filter with a raised cosine transition band. The filter has cutoff frequency F0, transition bandwidth df, and sampling frequency fs, all in hertz. df must be small enough so that F0 ± df/2 is between 0 and fs/2. The coefficients in b are normalized so that the nominal passband gain is always equal to 1. Specify fs as the empty vector [] to use the default value fs = 2.
b = firrcos(n,F0,df)
uses a default sampling frequency of fs = 2.
b interprets the third argument, = firrcos(n,F0,r,fs,'rolloff')
r, as the rolloff factor instead of the transition bandwidth, df. r must be in the range [0,1].
b designs either a normal raised cosine filter or a square root raised cosine filter according to how you specify of the string = firrcos(...,'type')
'type'. Specify 'type' as:
'normal', for a regular raised cosine filter. This is the default, and is also in effect when the 'type' argument is left empty, [].
'sqrt', for a square root raised cosine filter.
b specifies an integer delay in the range = firrcos(...,'type',delay)
[0,n+1]. The default is n/2 for even n and (n+1)/2 for odd n.
b applies a length = firrcos(...,'type',delay,window)
n+1 window to the designed filter to reduce the ripple in the frequency response. window must be a length n+1 column vector. If no window is specified, a rectangular (rectwin) window is used. Care must be exercised when using a window with a delay other than the default.
[b,a] always returns = firrcos(...)
a = 1.
ExamplesExamples
Design an order 20 raised cosine FIR filter with cutoff frequency 0.25 of the Nyquist frequency and a transition bandwidth of 0.25:
See Also
| | firls | flattopwin | |
