g=warpedblfilter(winname,fsupp,fc,fs,freqtoscale,scaletofreq);
| winname | Name of prototype. |
| fsupp | Support length of the prototype (in scale units). |
| fc | Centre frequency (in Hz). |
| fs | Sampling rate |
| freqtoscale | Function handle to convert Hz to scale units |
| scaletofreq | Function to convert scale units into Hz. |
| g | Filter definition, see blfilter. |
warpedblfilter(winname,fsupp,fc,fs,freqtoscale,scaletofreq) constructs a band-limited filter that is warped on a given frequency scale. The parameter winname specifies the basic shape of the frequency response. The name must be one of the shapes accepted by firwin. The support of the frequency response measured on the selected frequency scale is specified by fsupp, the centre frequency by fc and the scale by the function handle freqtoscale of a function that converts Hz into the choosen scale and scaletofreq doing the inverse.
If one of the inputs is a vector, the output will be a cell array with one entry in the cell array for each element in the vector. If more input are vectors, they must have the same size and shape and the the filters will be generated by stepping through the vectors. This is a quick way to create filters for filterbank and ufilterbank.
warpedblfilter accepts the following optional parameters:
| 'complex' | Make the filter complex valued if the centre frequency is non-zero. This is the default. |
| 'real' | Make the filter real-valued if the centre frequency is non-zero. |
| 'symmetric' | The filters with fc<0 (or fc>fs/2) will be created on the positive frequencies and mirrored. This allows using freqtoscale defined only for the positive numbers. |
| 'delay',d | Set the delay of the filter. Default value is zero. |
| 'scal',s | Scale the filter by the constant s. This can be useful to equalize channels in a filterbank. |
It is possible to normalize the transfer function of the filter by passing any of the flags from the setnorm function. The default normalization is 'energy'.
The filter can be used in the pfilt routine to filter a signal, or in can be placed in a cell-array for use with filterbank or ufilterbank.
The output format is the same as that of blfilter.