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Variable Bandwidth FIR Filter

Design tunable bandwidth FIR filter

  • Variable Bandwidth FIR Filter block

Libraries:
DSP System Toolbox / Filtering / Filter Designs

Description

The Variable Bandwidth FIR Filter block filters each channel of the input signal over time using the specified FIR filter specifications. This block offers tunable filter design parameters, which enable you to tune the filter characteristics while the simulation is running.

The block designs the FIR filter according to the filter parameters specified in the block dialog box. The output port properties, such as datatype, complexity, and dimension, are identical to the input port properties.

This block also supports SIMD code generation. For details, see Code Generation.

Ports

Input

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Specify the data input as a vector or a matrix. The block treats each column of the input signal as a separate channel. If the input is a two-dimensional signal, the first dimension represents the channel length (or frame size) and the second dimension represents the number of channels. If the input is a one-dimensional signal, then the block interprets it as having a single channel.

The block accepts variable-size input signals, that is, you can change the size of each input channel during simulation but you cannot change the number of channels.

This port is unnamed until you select one of these parameters:

  • Specify cutoff frequency from input port

  • Specify center frequency from input port

  • Specify bandwidth from input port

Data Types: single | double
Complex Number Support: Yes

Specify the cutoff frequency of the FIR filter as a real positive scalar in Hz or in normalized frequency units (since R2023a).

Dependencies

To enable this port, select the Specify cutoff frequency from input port parameter.

Data Types: single | double

Specify the center frequency of the FIR filter as a real positive scalar in Hz or in normalized frequency units (since R2023a).

Dependencies

To enable this port, select the Specify center frequency from input port parameter.

Data Types: single | double

Specify the bandwidth of the FIR filter as a real positive scalar in Hz or in normalized frequency units (since R2023a).

Dependencies

To enable this port, select the Specify bandwidth from input port parameter.

Data Types: single | double

Output

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Filtered output, returned as a vector or a matrix. The size, data type, and complexity of the output signal matches that of the input signal.

Data Types: single | double
Complex Number Support: Yes

Parameters

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Specify the order of the FIR filter as a positive integer scalar.

Specify the type of FIR filter. You can set this parameter to:

  • Lowpass

  • Highpass

  • Bandpass

  • Bandstop

When you select this check box, specify the cutoff frequency through the Fcut port. When you clear this check box, specify the cutoff frequency in the block dialog box through the Filter cutoff frequency parameter.

Dependency

To enable this parameter, set Filter type to Lowpass or Highpass.

Specify the cutoff frequency of the FIR filter as a real positive scalar in Hz or in normalized frequency units (since R2023a).

If you set the Sample rate mode parameter to:

  • Specify on dialog or Inherit from input port –– The value of the filter cutoff frequency is in Hz and must be less than half the value of the input sample rate.

  • Use normalized frequency (0 to 1) –– The value of the filter cutoff frequency is in normalized frequency units. The value must be a positive scalar less than 1.0.

(since R2023a)

Tunable: Yes

Dependencies

To enable this parameter:

  • Set Filter type to Lowpass or Highpass.

  • Clear the Specify cutoff frequency from input port parameter.

When you select this check box, specify the center frequency through the Fc port. When you clear this check box, specify the center frequency in the block dialog box through the Filter center frequency parameter.

Dependencies

To enable this parameter, set Filter type to Bandpass or Bandstop.

Specify the center frequency of the FIR filter as a real positive scalar in Hz or in normalized frequency units (since R2023a).

If you set the Sample rate mode parameter to:

  • Specify on dialog or Inherit from input port –– The value of the filter center frequency is in Hz and must be less than half the value of the input sample rate.

  • Use normalized frequency (0 to 1) –– The value of the filter center frequency is in normalized frequency units. The value must be a positive scalar less than 1.0.

(since R2023a)

Tunable: Yes

Dependencies

To enable this parameter:

  • Set Filter type to Bandpass or Bandstop.

  • Clear the Specify center frequency from input port parameter.

When you select this check box, specify the filter bandwidth through the BW port. When you clear this check box, specify the filter bandwidth in the block dialog box through the Filter bandwidth parameter.

Dependency

To enable this parameter, set Filter type to Bandpass or Bandstop.

Specify the bandwidth of the FIR filter as a real positive scalar in Hz or in normalized frequency units (since R2023a).

If you set the Sample rate mode parameter to:

  • Specify on dialog or Inherit from input port –– The value of the filter bandwidth is in Hz and must be less than half the value of the input sample rate.

  • Use normalized frequency (0 to 1) –– The value of the filter bandwidth is in normalized frequency units. The value must be a positive scalar less than 1.0.

(since R2023a)

Tunable: Yes

Dependencies

To enable this parameter:

  • Set Filter type to Bandpass or Bandstop.

  • Clear the Specify bandwidth from input port parameter.

Specify the window function used to design the FIR filter. You can set this parameter to:

  • Hann

  • Hamming

  • Chebyshev

  • Kaiser

Specify the sidelobe attenuation of the Chebyshev window as a real positive scalar.

Dependencies

To enable this parameter, set Window function to Chebyshev.

Specify the Kaiser window parameter as a real scalar.

Dependencies

To enable this parameter, set Window function to Kaiser.

Since R2023a

Specify the input sample rate using one of these options:

  • Specify on dialog –– Specify the input sample rate in the block dialog box using the Input sample rate (Hz) parameter.

  • Inherit from input port –– The block inherits the sample rate from the input signal as N / Ts, where N is the frame size of the input signal and Ts is the sample time of the input signal.

  • Use normalized frequency (0 to 1) –– Specify the filter cutoff frequency, center frequency, and the filter bandwidth in normalized frequency units (0 to 1).

Specify the sample rate of the input signal as a positive scalar in Hz.

Dependencies

To enable this parameter, set the Sample rate mode parameter to Specify on dialog. (since R2023a)

Clicking this button opens the filter visualizer and displays the magnitude response of the variable bandwidth FIR filter. The response is based on the parameters you select in the block dialog box. To update the magnitude response while the filter visualizer is running, modify the parameters in the dialog box and click Apply.

You can configure the plot settings and the signal measurements from the interface of the visualizer.

On the Scope tab of the filter visualizer toolstrip, the Configuration section allows you to modify the plot settings. On the Measurements tab, you can measure the signal statistics, place data cursors, and display the peak values of the selected signal.

For more details on the filter visualizer interface and its tools, see Configure Filter Visualizer.

Dependencies

To enable this button, do not specify any filter specifications from the input port.

Specify the type of simulation to run. You can set this parameter to:

  • Interpreted execution –– Simulate model using the MATLAB® interpreter. This option shortens startup time.

  • 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.

Block Characteristics

Data Types

double | single

Multidimensional Signals

No

Variable-Size Signals

Yes

Algorithms

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References

[1] Jarske, P., Y. Neuvo, and S. K. Mitra. "A Simple Approach to the Design of Linear Phase FIR Digital Filters with Variable Characteristics." Signal Processing 14, no. 4 *(1988): 313-326.

Extended Capabilities

Version History

Introduced in R2015a

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