Filter Design Toolbox™

cumsec - Vector of SOS filters for cumulative sections

Syntax

h = cumsec(hd)
h = cumsec(hd,indices)
h = cumsec(hd,indices,secondary)
cumsec(hd,...)

Description

h = cumsec(hd) returns a vector h of SOS filter objects with the cumulative sections. Each element in h is a filter with the structure of the original filter. The first element is the first filter section of hd. The second element of h is a filter that represents the combination of the first and second sections of hd. The third element of h is a filter which combines sections 1, 2, and 3 of hd. this pattern continues until the final element of h contains all the sections of hd and should be identical to hd.

h = cumsec(hd,indices) returns a vector h of SOS filter objects whose indices into the original filter are in the vector indices. Now you can specify the filter sections cumsec uses to compute the cumulative responses.

h = cumsec(hd,indices,secondary) when secondary is true, cumsec uses the secondary scaling points in the sections to determine where the sections should be split. This option applies only when hd is a df2sos and df1tsos filter. For these second-order section structures, the secondary scaling points refer to the scaling locations between the recursive and the nonrecursive parts of the section (the "middle" of the section). Argument secondary accepts either true or false. By default, secondary is false.

cumsec(hd,...) without an output arguments uses FVTool to plot the magnitude response of the cumulative sections.

Examples

To demonstrate how cumsec works, this example plots the relative responses of the sections of a sixth-order filter SOS filter with three sections. Each curve adds one more section to form the filter response.

hs = fdesign.lowpass('n,fc',6,.4);
hd = butter(hs);
h = cumsec(hd);
hfvt = fvtool(h);
legend(hfvt,'First Section','First Two Sections','Overall 
Filter');

See Also

scale, scalecheck

cost

denormalize