cumsec

Cumulative second-order section of the biquadratic filter

Description

example

sect = cumsec(sysobj) returns a cell array, sect, which contains cumulative sections of the biquadratic filter System object™, sysobj. Each element in sect is a filter with the structure of the original filter. The first element is the first filter section of the biquadratic filter. The second element of sect is a filter that represents the combination of the first and second sections of the biquadratic filter. The third element of sect is a filter which combines sections 1, 2, and 3 of the biquadratic filter. This pattern continues until the final element of sect contains all the sections of the biquadratic filter and should be identical to the biquadratic filter.

sect = cumsec(sysobj,indices) returns the cumulative sections of the biquadratic filter object whose indices in the original filter are in the vector indices.

sect = cumsec(sysobj,indices,secondary) uses the secondary scaling points secondary in the sections to determine where the sections should be split when secondary is true. secondary is false by default. This option only applies for biquadratic filter objects with 'Direct form II' and 'Direct form I transposed' structures. For these structures, the secondary scaling points refer to the location between the recursive and the nonrecursive part, that is the 'middle' of the section.

cumsec(sysobj,...) plots the magnitude response of the cumulative sections using fvtool.

sect = cumsec(sysobj,'Arithmetic',arithType) returns the cumulative sections of the biquadratic filter object with the arithmetic specified in arithType.

Examples

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This example plots the relative responses of the sections of a sixth-order filter with three sections. Each curve adds one more section to form the filter response.

Lowpass = fdesign.lowpass('n,fc',6,.4); ButterLowpass = butter(Lowpass,'SystemObject',true); 
CumSections = cumsec(ButterLowpass); hfvt = fvtool(CumSections{1},CumSections{2},CumSections{3}); 
legend(hfvt,'First Section','First Two Sections','Overall  Filter');

Input Arguments

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Input filter, specified as one of the following System objects:

Filter indices. Use indices to specify the filter sections cumsec uses to compute the cumulative responses.

This option applies only when sysobj has the df2sos and df1tsos structures. 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.

Specify the arithmetic used during analysis. When the arithmetic input is not specified and the filter System object is unlocked, the analysis tool assumes a double-precision filter. The 'Arithmetic' property set to 'Fixed' applies only to filter System objects with fixed-point properties.

Introduced in R2011a