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Differentiator Filter

Direct form FIR fullband differentiator filter

Library

Filtering / Filter Designs

dspfdesign

  • Differentiator Filter block

Description

TheDifferentiator Filterblock applies a fullband differentiator filter on the input signal to differentiate all its frequency components. The block uses an FIR equiripple filter design to design the differentiator filter. The ideal frequency response of the differentiator is D ( ω ) = j ω for − π ≤ ω ≤ π 。

You can design the filter with minimum order or with a specifies order.

The input signal can be a real- or complex-valued column vector or matrix. If the input signal is a matrix, each column of the matrix is treated as an independent channel.

This block supports variable-size input, enabling you to change the channel length during simulation. The output port properties, such as data type, complexity, and dimension, are identical to the input port properties. The block supports fixed-point operations.

This block also supports SIMD code generation. For details, seeCode Generation。

Examples

Dialog Box

Main Tab

Design minimum order filter

When you select this check box, the block designs a filter with the minimum order, with the passband ripple specified inMaximum passband ripple (dB)。When you clear this check box, specify the order of the filter inFilter order。

By default, this check box is selected.

Filter order

Filter order of the differentiator filter, specified as an odd positive scalar integer. You can specify the filter order only whenDesign minimum order filtercheck box is not selected. The default is31。

Maximum passband ripple (dB)

Maximum ripple of the filter response in the passband, specified as a real positive scalar in dB. The default is0.1。

Scale filter coefficients

When you select this check box, the filter coefficients are scaled to preserve the input dynamic range. By default, this check box is not selected.

View Filter Response

Opens the Filter Visualization Tool (fvtool) and displays the magnitude and phase response of theDifferentiator Filterblock. The response is based on the block dialog box parameters. Changes made to these parameters update FVTool.

To update the magnitude response while FVTool is running, modify the dialog box parameters and clickApply。

Simulate using

Type of simulation to run. You can set this parameter to:

  • Interpreted execution(default)

    Simulate model using the MATLAB®interpreter. This option shortens startup time and has faster simulation speed thanCode generation。

  • Code generation

    Simulate model using generated C code. The first time you run a simulation, Simulink®generates C code for the block. The C code is reused for subsequent simulations, as long as the model does not change. This option requires additional startup time but provides faster subsequent simulations.

Data Types Tab

Rounding mode

Rounding method for the output fixed-point operations. The rounding methods areCeiling,Convergent,Floor,Nearest,Round,Simplest, andZero。The default isFloor。

Coefficients

Fixed-point data type of the coefficients, specified as one of the following:

  • fixdt(1,16)(default) — Signed fixed-point data type of word length16, with binary point scaling. The block determines the fraction length automatically from the coefficient values such that the coefficients occupy the maximum representable range without overflowing.

  • fixdt(1,16,0)— Signed fixed-point data type of word length16and fraction length0。You can change the fraction length to any other integer value.

  • — Specify the data type using an expression that evaluates to a data type object, for example, numeric type (fixdt([ ],16,15)). Specify the sign mode of this data type as[ ]ortrue。

  • Refresh Data Type— Refresh to the default data type.

Click theShow data type assistantbuttonto display the data type assistant, which helps you set the stage input parameter.

SeeSpecify Data Types Using Data Type Assistant(Simulink)for more information.

输出的字长是一样的词length of the input. The fraction length of the output is computed such that the entire dynamic range of the output can be represented without overflow. For details on how the block computes the fraction length, seeFixed-Point Precision Rules for Avoiding Overflow in FIR Filters。

Supported Data Types

Port Supported Data Types

Input

  • Double-precision floating point

  • Single-precision floating point

  • Fixed point (signed or unsigned)

Output

  • Double-precision floating point

  • Single-precision floating point

  • Fixed point (signed or unsigned)

Algorithms

expand all

Extended Capabilities

Fixed-Point Conversion
Design and simulate fixed-point systems using Fixed-Point Designer™.

Version History

Introduced in R2015b

See Also

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