Design arbitrary response filter
Filtering / Filter Designs
This block brings the filter design capabilities of the
to the Simulink® environment.
See Arbitrary Response Filter Design Dialog Box — Main Pane for more information about the parameters of this block. The Data Types and Code Generation panes are not available for blocks in the DSP System Toolbox™ Filter Designs library.
This button opens the Filter Visualization Tool (
fvtool) from the Signal Processing Toolbox™ product.
You can use the tool to display:
Magnitude response, phase response, and group delay in the frequency domain.
Impulse response and step response in the time domain.
The tool also helps you evaluate filter performance by providing information about filter order, stability, and phase linearity. For more information on FVTool, see the Signal Processing Toolbox documentation.
In this group, you specify your filter format, such as the impulse response and the filter order.
the drop down list, where
FIR is the default.
When you choose an impulse response, the design methods and structures
you can use to implement your filter change accordingly.
the drop-down list. Selecting
the Order option so you can enter the filter
order. When you set the Impulse response to
you can specify different numerator and denominator orders. To specify
a different denominator order, you must select the Denominator
order check box.
Enter the order for FIR filter, or the order of the numerator for the IIR filter.
Select the check box and enter the denominator order. This option
is enabled only if
IIR is selected for Impulse
This option is available for FIR filters only. Select
Sample-rate converter. Your choice determines
the type of filter as well as the design methods and structures that
are available to implement your filter. By default, the block specifies
a single-rate filter.
the Decimation Factor or the Interpolation
Factor options respectively.
Sample-rate converter activates
Enter the decimation factor. This option is enabled only if
the Filter type is set to
converter. The default value is 2.
Enter the interpolation factor. This option is enabled only
if the Filter type is set to
converter. The default value is 2.
Select the number of bands in the filter. Multiband design is available for both FIR and IIR filters.
Specify the response as
Group delay is
only available for IIR designs.
Specify frequency units as either
which means normalized by the input sampling frequency, or select
Enter the input sampling frequency in the units specified in the Frequency units drop-down list. When you select the frequency units, this option is available.
These properties are modified automatically depending on the response chosen in the Specify response as drop-down list. Two or three columns are presented for input. The first column is always Frequencies. The other columns are Amplitudes, Magnitudes, Phases, or Frequency Response. Enter the corresponding vectors of values for each column.
Frequencies and Amplitudes —
These columns are presented for input if the response chosen in the Specify
response as drop-down list is
and Phases — These columns are presented
for input if the response chosen in the Specify response
as drop-down list is
Magnitudes and phases.
Frequencies and Frequency
response — These columns are presented for input
if the response chosen in the Specify response as drop-down
Select the design method for the filter. Different methods are enabled depending on the defining parameters entered in the previous sections.
The options for each design are specific for each design method. This section does not present all of the available options for all designs and design methods. There are many more that you encounter as you select different design methods and filter specifications.
Window — Replace the square
brackets with the name of a
or function handle. For example,
If the window function takes parameters other than the length, use
a cell array. For example,
Density factor — Valid
when the Design method is
Density factor controls the density of the frequency grid over which
the design method optimization evaluates your filter response function.
The number of equally spaced points in the grid is the value you enter
for Density factor times (filter order + 1).
Increasing the value creates a filter that more closely approximates an ideal equiripple filter but increases the time required to design the filter. The default value of 16 represents a reasonable trade-off between the accurate approximation to the ideal filter and the time to design the filter.
Phase constraint — Valid
when the Design method is
you have the DSP System Toolbox installed, and Specify
response as is set to
Choose one of
Weights — Valid when the Design
the weights in Weights to weight the error for
a single-band design. If you have multiple frequency bands, the Weights design
option changes to B1 Weights, B2 Weights to
designate the separate bands.
Select the structure for the filter, available for the corresponding design method.
Select this check box to implement the filter as a subsystem of basic Simulink blocks. Clear the check box to implement the filter as a high-level subsystem. By default, this check box is cleared.
The high-level implementation provides better compatibility across various filter structures, especially filters that would contain algebraic loops when constructed using basic elements. On the other hand, using basic elements enables the following optimization parameters:
Optimize for zero gains — Terminate chains that contain Gain blocks with a gain of zero.
Optimize for unit gains — Remove Gain blocks that scale by a factor of one.
Optimize for delay chains — Substitute delay chains made up of n unit delays with a single delay by n.
Optimize for negative gains — Use subtraction in Sum blocks instead of negative gains in Gain blocks.
Select this check box to scale unit gains between sections in SOS filters. This parameter is available only for SOS filters.
Specify how the block should process the input. The available options may vary depending on he settings of the Filter Structure and Use basic elements for filter customization parameters. You can set this parameter to one of the following options:
Columns as channels (frame based) —
When you select this option, the block treats each column of the input
as a separate channel.
Elements as channels (sample based) —
When you select this option, the block treats each element of the
input as a separate channel.
When the Filter type parameter specifies a multirate filter, select the rate processing rule for the block from following options:
Enforce single-rate processing —
When you select this option, the block maintains the sample rate of
Allow multirate processing —
When you select this option, the block adjusts the rate at the output
to accommodate an increased or reduced number of samples. To select
this option, you must set the Input processing parameter
Elements as channels (sample based).
Select this check box to enable the specification of coefficients using MATLAB® variables. The available coefficient names differ depending on the filter structure. Using symbolic names allows tuning of filter coefficients in generated code. By default, this check box is cleared.
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