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lagrange

Fractional delay filter from fdesign.fracdelay specification object

Syntax

Hd = design(d,'lagrange')
hd = design(d,'lagrange',FilterStructure,structure)

Description

Hd = design(d,'lagrange') designs a fractional delay filter using the Lagrange method based on the specifications in d.

hd = design(d,'lagrange',FilterStructure,structure) specifies the Lagrange design method and the structure filter structure for hd. The sole valid filter structure string for structure is fd, describing the fractional delay structure.

Examples

This example uses a fractional delay of 0.30 samples. The help and designopts commands provide the details about designing fractional delay filters.

d=fdesign.fracdelay(.30)
 
d =
 
               Response: 'Fractional Delay'
          Specification: 'N'               
            Description: {'Filter Order'}  
              FracDelay: 0.3               
    NormalizedFrequency: true              
            FilterOrder: 3                 
                                           
designmethods(d)

Design Methods for class fdesign.fracdelay (N):

lagrange

help(d,'lagrange')

DESIGN Design a Lagrange fractional delay filter.
HD = DESIGN(D, 'lagrange') designs a Lagrange filter specified by the
  FDESIGN object D, and returns the DFILT object HD.
 
HD = DESIGN(..., 'FilterStructure', STRUCTURE) returns a filter with the
 structure STRUCTURE.  STRUCTURE is 'farrowfd' by default and can be any of
 the following:

'farrowfd'
'fd'
 
 % Example #1 - Design a linear Lagrange fractional delay filter of 0.2 samples.
 h = fdesign.fracdelay(0.2,'N',2);
 Hd = design(h, 'lagrange', 'FilterStructure', 'farrowfd')
 
 % Example #2 - Design a cubic Lagrange fractional delay filter
 Fs = 8000;      % Sampling frequency of 8kHz
 fdelay = 50e-6; % Fractional delay of 50 microseconds.
 h  = fdesign.fracdelay(fdelay,'N',3,Fs);
 Hd = design(h, 'lagrange', 'FilterStructure', 'farrowfd');

This example designs a linear Lagrange fractional delay filter where you set the delay to 0.2 seconds and the filter order N to 2.

h = fdesign.fracdelay(0.2,'N',2); 
hd = design(h,'lagrange','FilterStructure','farrowfd')

Design a cubic Lagrange fractional delay filter with filter order equal to 3.

Fs = 8000;      % Sampling frequency of 8 kHz.
fdelay = 50e-6; % Fractional delay of 50 microseconds.
h  = fdesign.fracdelay(fdelay,'N',3,Fs);
hd = design(h,'lagrange','FilterStructure','farrowfd');

References

Laakso, T. I., V. Välimäki, M. Karjalainen, and Unto K. Laine, "Splitting the Unit Delay - Tools for Fractional Delay Filter Design," IEEE® Signal Processing Magazine, Vol. 13, No. 1, pp. 30-60, January 1996.

Introduced in R2011a

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