Design differentiator filter
Filtering / Filter Designs
dspfdesign
This block brings the filter design capabilities of the
function
to the Simulink^{®} environment.filterbuilder
See Differentiator 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.
Polezero information.
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.
Select either Minimum
or Specify
(the
default). Selecting Specify
enables the Order option
so you can enter the filter order.
Enter the filter order. This option is enabled only if you set
the Order mode to Specify
.
The default order is 31.
Select Singlerate
, Decimator
, Interpolator
,
or Samplerate 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 singlerate filter.
Selecting Decimator
or Interpolator
activates
the Decimation Factor or the Interpolation
Factor options respectively.
Selecting Samplerate converter
activates
both factors.
Enter the decimation factor. This option is enabled only if
the Filter type is set to Decimator
or Samplerate
converter
. The default value is 2.
Enter the interpolation factor. This option is enabled only
if the Filter type is set to Interpolator
or Samplerate
converter
. The default value is 2.
The parameters in this group allow you to specify your filter response curve.
This option is only available when you specify the order of
the filter design. Supported options are Unconstrained
and Passband
edge and stopband edge
.
Use this parameter to specify whether your frequency settings
are normalized or in absolute frequency. Select Normalized
(0–1)
to enter frequencies in normalized form.
This behavior is the default. To enter frequencies in absolute values,
select one of the frequency units from the dropdown list—Hz
, kHz
, MHz
,
or GHz
. Selecting one of the unit options
enables the Input Fs parameter.
Fs, specified in the units you selected for Frequency units, defines the sampling frequency at the filter input. When you provide an input sampling frequency, all frequencies in the specifications are in the selected units as well. This parameter is available when you select one of the frequency options from the Frequency units list.
Enter the frequency at the end of the passband. Specify the value in either normalized frequency units or the absolute units you select in Frequency units.
Enter the frequency at the start of the stopband. Specify the value in either normalized frequency units or the absolute units you select in Frequency units.
Parameters in this group specify the filter response in the passbands and stopbands. These parameters are only available for minimumorder designs.
This option is only available when you specify the order of
your filter design. The available Magnitude constraints depend
on the value of the Frequency constraints parameter.
When you set the Frequency constraints parameter
to Unconstrained
, the Magnitude
constraints parameter must also be Unconstrained
.
When you set the Frequency constraints parameter
to Passband edge and stopband edge
, the Magnitude
constraints parameter can be Unconstrained
, Passband
ripple
, or Stopband attenuation
.
Specify the units for any parameter you provide in magnitude specifications. From the dropdown list, select one of the following options:
Linear
— Specify
the magnitude in linear units.
dB
— Specify the
magnitude in decibels (default).
Squared
— Specify
the magnitude in squared units.
Enter the filter ripple allowed in the passband in the units you choose for Magnitude units, either linear or decibels.
Enter the filter attenuation in the second stopband in the units you choose for Magnitude units, either linear or decibels.
The parameters in this group allow you to specify the design method and structure of your filter.
Lists the design methods available for the frequency and magnitude specifications you entered. When you change the specifications for a filter, such as changing the impulse response, the methods available to design filters changes as well.
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. The following options represent some of the most common ones available.
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 20 represents a reasonable trade between the accurate approximation to the ideal filter and the time to design the filter.
Passband weight. This option is only available for a specifiedorder
design when Frequency constraints is equal to Passband
edge and stopband edge
and the Design method is Equiripple
.
Stopband weight. This option is only available for a specifiedorder
design when Frequency constraints is equal to Passband
edge and stopband edge
and the Design method is Equiripple
.
For the filter specifications and design method you select, this parameter lists the filter structures available to implement your filter. By default, FIR filters use directform structure.
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 highlevel subsystem. By default, this check box is cleared.
The highlevel 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.
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.
Note:
The 
When the Filter type parameter specifies a multirate filter, select the rate processing rule for the block from following options:
Enforce singlerate processing
—
When you select this option, the block maintains the sample rate of
the input.
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
to 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.
Port  Supported Data Types 

Input 

Output 
