Biquad Filter

Model biquadratic IIR (SOS) filters

Library:
DSP System Toolbox / Filtering / Filter Implementations
DSP System Toolbox HDL Support / Filtering

Description

The Biquad Filter block independently filters each channel of the input signal with the specified biquadratic infinite impulse response (IIR) filter. When you specify the filter coefficients in the dialog box, the block implements static filters with fixed coefficients. When you provide the filter coefficients through an input port, you can tune the coefficients during simulation.

The Biquad Filter block supports the Simulink^® state logging feature. See State (Simulink) for more information.

Ports

Input

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`In` — Data input
vector | matrix

Data input to the block, specified as a vector or a matrix. This block supports variable-size input signals, enabling you to change the input frame size (number of rows) during simulation. However, the number of channels (number of columns) must remain constant.

If the input is fixed-point, it must be signed fixed-point with binary point scaling.

This port is unnamed unless you set the Coefficient source to Input port(s).

Data Types: single | double | int8 | int16 | int32 | int64 | fixed point
Complex Number Support: Yes

`Num` — Numerator coefficients
matrix

Numerator coefficients of the biquad filter, specified as a 3-by-N matrix, where N is the number of biquad filter sections.

If Num is fixed-point, it must be signed fixed-point with binary point scaling.

Dependencies

This port appears only when you set the Coefficient source to Input port(s).

Data Types: single | double | int8 | int16 | int32 | int64 | fixed point

`Den` — Denominator coefficients
matrix

Denominator coefficients of the biquad filter, specified as a 2-by-N matrix, where N is the number of biquad filter sections.

If Den is fixed-point, it must be signed fixed-point with binary point scaling.

Dependencies

This port appears only when you set the Coefficient source to Input port(s).

Data Types: single | double | int8 | int16 | int32 | int64 | fixed point

`g` — Scale values
row vector

Scale values of the biquad filter, specified as a 1-by-(N+1) vector, where N is the number of biquad filter sections.

If g is fixed-point, it must be signed fixed-point with binary point scaling.

Dependencies

This port appears only when you set the Coefficient source to Input port(s).

Data Types: single | double | int8 | int16 | int32 | int64 | fixed point

Output

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`Out` — Filtered output
vector | matrix

Filtered output, returned as a vector or a matrix.

The output dimensions always equal the dimensions of the input signal. The output of this block numerically matches the outputs of the dsp.BiquadFilter System object™.

If Out is fixed-point, it must be signed fixed-point with binary point scaling.

This port is unnamed unless you set the Coefficient source to Input port(s).

Data Types: single | double | int8 | int16 | int32 | int64 | fixed point
Complex Number Support: Yes

Parameters

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Main Tab

`Coefficient source` — Mode of operation
`Dialog parameters` (default) | `Input port(s)` | `Filter object`

The Biquad Filter block can operate in three different modes:

Dialog parameters — Enter information about the filter, such as structure and coefficients, in the block mask.
Input port(s) — Enter information about the filter structure in the block mask using the Filter structure parameter. The filter coefficients come into the block through additional input ports that appear on the block icon:
- Num — Specify numerator coefficients.
- Den — Specify denominator coefficients.
- g — Specify scale values.
The block assumes the first denominator coefficients and of each section to be 1. This configuration is applicable when the SOSMatrixSource property is 'Input port' and the ScaleValuesInputPort property is true. The reason you would need to specify Num and Den instead of the SOSMatrix, is that in Fixed-Point operation, the numerators, and denominators can have different fraction lengths. Therefore, there is a need to be able to pass the data of the numerator with a fixed-point type different from that of the denominator.
Filter object — Specify the filter using a dsp.BiquadFilter System object.

`Filter` — Name of filter object
`BQF` (default) | `dsp.BiquadFilter System object` name

Specify the name of the discrete-time filter that you want the block to implement. You must specify the filter as a dsp.BiquadFilter System object.

You can define the System object in the block mask or in a MATLAB^® workspace variable.

For information on creating System objects, see Define Basic System Objects.

Dependencies

This parameter is visible only when Coefficient source is set to Filter object.

`Filter structure` — Filter structure
`Direct form II transposed` (default) | `Direct form I` | `Direct form I transposed` | `Direct form II`

Specify the filter structure.

Dependencies

This parameter is visible only when Coefficient source is set to Dialog parameters or Input port(s).

`SOS Matrix (Mx6)` — SOS matrix
`[1 0.3 0.4 1 0.1 0.2]` (default) | M-by-6 matrix

Specify an M-by-6 matrix, where M is the number of sections in the second-order section filter. Each row of the SOS matrix contains the numerator and denominator coefficients (b_ik and a_ik) of the corresponding section in the filter.

$[\begin{matrix} b_{01} & b_{11} & b_{21} & a_{01} & a_{11} & a_{21} \\ b_{02} & b_{12} & b_{22} & a_{02} & a_{12} & a_{22} \\ ⋮ & ⋮ & ⋮ & ⋮ & ⋮ & ⋮ \\ b_{0 M} & b_{1 M} & b_{2 M} & a_{0 M} & a_{1 M} & a_{2 M} \end{matrix}]$

The leading denominator coefficients [a₀₁ a₀₂ ... a_0N] are treated as 1s, regardless of their actual values. No scaling is applied to the SOS matrix when a0 is not 1.

The ss2sos and tf2sos functions convert a state-space or transfer function description of your filter into the second-order section description used by this block.

Dependencies

This parameter is visible only when Coefficient source is set to Dialog parameters.

`Scale values` — Scale values
`1` (default) | scalar | vector

Specify scale values to be used between SOS sections. You can specify a real-valued scalar or a vector of length M+1:

When you enter a scalar, the value specifies the gain value before the first section of the second-order filter. The rest of the gain values default to 1.
When you enter a vector of M+1 values, each value specifies a separate section of the filter. For example, the first element is the first gain value, the second element is the second gain value, and so on.

Select the Optimize unity scale values check box to optimize your simulation when one or more scale values equal 1. Selecting this option removes the unity gains so that the values are treated like Simulink lines or wires. In some fixed-point cases when there are unity scale values, selecting this parameter also omits certain casts. Refer to the Fixed-Point Conversion section under Extended Capabilities for more information.

Dependencies

This parameter is visible only when Coefficient source is set to Dialog parameters.

`Initial conditions` — Initial conditions
`0` (default) | scalar | vector

Specify the initial conditions of the filter states.

The Biquad Filter block initializes the internal filter states to zero by default. Optionally, use the Initial conditions parameter to specify nonzero initial states for the filter delays.

To determine the number of initial conditions you must specify and how to specify them, see the following table on valid initial conditions.

Valid Initial Conditions

Initial Condition	Description
Scalar	The block initializes all delay elements in the filter to the scalar value.
Vector or matrix (for applying different delay elements to each channel)	Each vector or matrix element specifies a unique initial condition for a corresponding delay element in a corresponding channel. M is the number of sections, and N is the number of input channels: The vector length must equal the number of delay elements in the filter, 2M. The matrix must have the same number of rows as the number of delay elements in the filter 2MN. The matrix must also have one column for each channel of the input signal.

Initial Condition

Description

Scalar

The block initializes all delay elements in the filter to the scalar value.

Vector or matrix
(for applying different delay elements to each channel)

Each vector or matrix element specifies a unique initial condition for a corresponding delay element in a corresponding channel. M is the number of sections, and N is the number of input channels:

The vector length must equal the number of delay elements in the filter, 2M.
The matrix must have the same number of rows as the number of delay elements in the filter 2MN. The matrix must also have one column for each channel of the input signal.

Dependencies

This parameter is only visible when Coefficient source is set to Dialog parameters or Input port(s) and the Filter structure is set to Direct form II or Direct form II transposed.

`Initial conditions on zeros side` — Initial conditions on zeros side
`0` (default) | scalar | vector

Specify the initial conditions for the filter states on the side of the filter structure with the zeros (b₀, b₁,b₂, ...).

The Biquad Filter block initializes the internal filter states to zero by default. Optionally, use the Initial conditions on zeros side parameter to specify nonzero initial states for the filter delays. For an example, see ex_biquad_filter_ref.

To determine the number of initial conditions you must specify and how to specify them, see the following table on valid initial conditions.

Valid Initial Conditions

Initial Condition	Description
Scalar	The block initializes all delay elements in the filter to the scalar value.
Vector or matrix (for applying different delay elements to each channel)	Each vector or matrix element specifies a unique initial condition for a corresponding delay element in a corresponding channel. Where M is the number of sections and N is the number of input channels: The vector length must equal the number of delay elements in the filter, 2M. The matrix must have the same number of rows as the number of delay elements in the filter 2MN. The matrix must also have one column for each channel of the input signal.

Initial Condition

Description

Scalar

The block initializes all delay elements in the filter to the scalar value.

Vector or matrix
(for applying different delay elements to each channel)

Each vector or matrix element specifies a unique initial condition for a corresponding delay element in a corresponding channel. Where M is the number of sections and N is the number of input channels:

The vector length must equal the number of delay elements in the filter, 2M.
The matrix must have the same number of rows as the number of delay elements in the filter 2MN. The matrix must also have one column for each channel of the input signal.

Dependencies

This parameter is visible only when Coefficient source is set to Dialog parameters or Input port(s) and the Filter structure is set to Direct form I or Direct form I transposed.

`Initial conditions on poles side` — Initial conditions on poles side
`0` (default) | scalar | vector

Specify the initial conditions for the filter states on the side of the filter structure with the poles (a₀, a₁, a₂, ...).

The Biquad Filter block initializes the internal filter states to zero by default. Optionally, use the Initial conditions on poles side parameter to specify nonzero initial states for the filter delays. For an example, see ex_biquad_filter_ref.

To determine the number of initial conditions you must specify and how to specify them, see the following table on valid initial conditions.

Valid Initial Conditions

Initial Condition	Description
Scalar	The block initializes all delay elements in the filter to the scalar value.
Vector or matrix (for applying different delay elements to each channel)	Each vector or matrix element specifies a unique initial condition for a corresponding delay element in a corresponding channel. Where M is the number of sections and N is the number of input channels: The vector length must equal the number of delay elements in the filter, 2M. The matrix must have the same number of rows as the number of delay elements in the filter 2MN. The matrix must also have one column for each channel of the input signal.

Initial Condition

Description

Scalar

The block initializes all delay elements in the filter to the scalar value.

Vector or matrix
(for applying different delay elements to each channel)

The vector length must equal the number of delay elements in the filter, 2M.
The matrix must have the same number of rows as the number of delay elements in the filter 2MN. The matrix must also have one column for each channel of the input signal.

Dependencies

This parameter is visible only when Coefficient source is set to Dialog parameters or Input port(s) and the Filter structure is set to Direct form I or Direct form I transposed.

`Scale values mode` — Mode to specify scale values
`Specify via input port (g)` (default) | `Assume all are unity and optimize`

Choose how to specify the scale values to use between filter sections. When you select Specify via input port (g), you enter the scale values as a 2-D vector at port g. When you select Assume all are unity and optimize, all scale values are removed and treated like Simulink lines or wires.

Dependencies

This parameter is visible only when Coefficient source is set to Input port(s).

`Action when the a0 values of the SOS matrix are not one` — Action when a0 values of SOS matrix are not one
`Warning` (default) | `None` | `Error`

Specify the action the block should perform when the SOS matrix a_0j values do not equal one. The action can be Warning, Error, or None.

When you choose None, the leading coefficients a_0j are treated as 1's, regardless of their actual values. No scaling is applied on the SOS matrix when a0 is not 1.

Dependencies

This parameter is visible only when Coefficient source is set to Dialog parameters.

`Optimize unity scale values` — Optimize unity scale values
`on` (default) | `off`

Select this check box to optimize your simulation when one or more scale values equal 1. Selecting this option removes the unity gains so that the values are treated like Simulink lines or wires. In some fixed-point cases when there are unity scale values, selecting this parameter also omits certain casts. See the Fixed Point section under Extended Capabilities for more information.

Dependencies

This parameter is visible only when Coefficient source is set to Dialog parameters.

`Input processing` — Input processing
`Columns as channels (frame based)` (default) | `Elements as channels (sample based)`

Specify how the block should process the input. If the input is an M-by-N matrix, you can set this parameter to:

Columns as channels (frame based) (default) — The block treats each column as a separate channel. In this mode, the block creates M instances of the same filter, each with its own independent state buffer. Each of the M filters process N input samples at every Simulink time step.
Elements as channels (sample based) — The block treats each element as a separate channel. In this mode, the block creates MN instances of the same filter, each with its own independent state buffer. Each filter processes one input sample at every Simulink time step.

`View Filter Response` — View filter response
button

This button opens the Filter Visualization Tool (fvtool) and displays the filter response of the filter specified in the dialog.

Note

When you make changes to the filter parameters on the block dialog, you must click the Apply button before using the View Filter Response button.

Data Types Tab

Note

This tab appears only when you set Coefficient source to either Dialog parameters or Input port(s). When the Coefficient source is set to Filter object, the data types specified in the filter object properties are used by the block.

`Rounding mode` — Rounding mode
`Floor` (default) | `Ceiling` | `Convergent` | `Nearest` | `Round` | `Simplest` | `Zero`

Specify the rounding mode for fixed-point operations.

For more details, see rounding mode. The filter coefficients do not obey this parameter; instead, they always round to Nearest.

`Saturate on integer overflow` — Method of overflow action
`off` (default) | `on`

When you select this parameter, the block saturates the result of its fixed-point operation. When you clear this parameter, the block wraps the result of its fixed-point operation. For details on saturate and wrap, see overflow mode for fixed-point operations.

The filter coefficients are always saturated and do not obey this parameter.

`Section input` — Section input data type
`Same as input` (default) | `Binary point scaling`

Choose how you specify the word and fraction lengths of the fixed-point data type going into each section of a biquadratic filter. See the Fixed-Point Conversion section under Extended Capabilities for illustrations depicting the use of the section input data type in this block. When you select:

Same as input — Word length and fraction length characteristics of the Section input data type match those of the input to the block.
Binary point scaling — Enter the word and fraction lengths of the section input, in bits.

`Section output` — Section output data type
`Same as section input` (default) | `Binary point scaling`

Choose how you specify the word and fraction lengths of the fixed-point data type coming out of each section of a biquadratic filter. See the Fixed-Point Conversion section under Extended Capabilities for illustrations depicting the use of the section output data type in this block. When you select:

Same as section input — Word length and fraction length characteristics of the Section output data type match with those of the input to the block.
Binary point scaling — Enter the word and fraction lengths of the section output, in bits.

`Multiplicand` — Multiplicand data type
`Same as output` (default) | `Binary point scaling`

Choose how you specify the word and fraction lengths of the multiplicand data type of a Direct form I transposed filter structure. See the Fixed-Point Conversion section under Extended Capabilities for illustrations depicting the use of the multiplicand data type in this block.

When you select:

Same as output — Word length and fraction length characteristics of the Multiplicand data type match with those of the output of the block.
Binary point scaling — Enter the word length and the fraction length of the multiplicand, in bits.

Dependencies

This parameter is visible only when the Filter structure parameter is set to Direct form I transposed.

`Coefficients` — Coefficients data type
`Same word length as input` (default) | `Specify word length` | `Binary point scaling`

Choose how you specify the word and fraction lengths of the filter coefficients (numerator, denominator, and scale value) when Coefficient source is set to Dialog parameters. See the Fixed-Point Conversion section under Extended Capabilities for illustrations depicting the use of the coefficient data types in this block. When you select:

Same word length as input — Word length of the filter coefficients matches that of the input to the block. In this mode, the block automatically sets the fraction length of the coefficients to the binary point-only scaling that provides the best precision possible given the value and word length of the coefficients.
Specify word length — Enter the word length of the coefficients, in bits. In this mode, the block automatically sets the fraction length of the coefficients to the binary point-only scaling that provides the best precision possible given the value and word length of the coefficients.
Binary point scaling — Enter the word length and the fraction length of the coefficients, in bits. If applicable, enter separate fraction lengths for the numerator and denominator coefficients.

The filter coefficients do not obey the Rounding mode and the Overflow mode parameters; instead, they are always saturated and rounded to Nearest.

Dependencies

This parameter is visible only when Coefficient source is set to Dialog parameters.

`Product output` — Product output data type
`Same as input` (default) | `Inherit via internal rule` | `Binary point scaling`

Specify how to designate the product output word and fraction lengths. See Multiplication Data Types and the Fixed-Point Conversion section under Extended Capabilities for illustrations depicting the use of the product output data type in this block. When you select:

Same as input — Product output word length and fraction length characteristics match those of the input to the block.
Inherit via internal rule — Product output word length and fraction lengths are computed based on full-precision rules. These rules prevent quantization from occurring within the block. Bits are added, as needed, so that no roundoff or overflow occurs. For more details, see Inherit via Internal Rule.
Binary point scaling — Enter the word length and the fraction length of the product output, in bits. If applicable, enter separate fraction lengths for the numerator and denominator product output data type.

`Accumulator` — Accumulator data type
`Same as product output` (default) | `Same as input` | `Binary point scaling`

Specify how to designate the accumulator word and fraction lengths. See Multiplication Data Types and the Fixed-Point Conversion section under Extended Capabilities for illustrations depicting the use of the accumulator data type in this block. When you select:

Same as input — Accumulator word and fraction length characteristics match those of the input to the block.
Same as product output — Accumulator word and fraction length characteristics match those of the product output.
Binary point scaling — Enter the word length and the fraction length of the accumulator, in bits. If applicable, enter separate fraction lengths for the numerator and denominator accumulator data type.

`States` — States data type
`Same as accumulator` (default) | `Same as input` | `Binary point scaling`

Specify how to designate the state word and fraction lengths when Coefficient source is set to Dialog parameters. See the Fixed-Point Conversion section under Extended Capabilities for illustrations depicting the use of the state data type in this block.

When you select:

Same as input — State word and fraction length characteristics match those of the input to the block.
Same as accumulator — State word and fraction length characteristics match those of the accumulator.
Binary point scaling — Enter the word length and the fraction length of the state, in bits. If applicable, enter separate fraction lengths for the numerator and denominator state data type.

Dependencies

This parameter is visible only when Filter structure is set to Direct form II or Direct form II transposed.

`Output` — Output data type
`Same as accumulator` (default) | `Same as input` | `Binary point scaling`

Choose how you specify the output word length and fraction length. See the Fixed-Point Conversion section under Extended Capabilities for illustrations depicting the use of the output data type in this block. When you select:

Same as input — Output word and fraction length characteristics match those of the input to the block.
Same as accumulator — Output word and fraction length characteristics match those of the accumulator.
Binary point scaling — Enter the word length and the fraction length of the output, in bits.

`Lock data type settings against changes by the fixed-point tools` — Lock data type settings
`off` (default) | `on`

Select this parameter to prevent the fixed-point tools from overriding the data types you specify on the block mask.

Model Examples

Code Generation for Parametric Audio Equalizer

Model an algorithm specification for a three band parametric equalizer which will be used for code generation.

Group Delay Estimation

Estimate the group delay of a filter in Simulink. Group delay is defined as -d(phi(f))/d(f). To estimate the group delay of the filter extract the phase response and compute its negative derivative with respect to frequency.

Parametric Audio Equalizer

Model an algorithm specification for a three band parametric equalizer

Block Characteristics

Data Types	`double` \| `fixed point` \| `integer` \| `single`
Direct Feedthrough	`no`
Multidimensional Signals	`no`
Variable-Size Signals	`yes`
Zero-Crossing Detection	`no`

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

HDL Code Generation
Generate Verilog and VHDL code for FPGA and ASIC designs using HDL Coder™.

HDL Coder™ provides additional configuration options that affect HDL implementation and synthesized logic.

Programmable Filter Support

HDL Coder supports programmable filters for Biquad Filter blocks.

On the filter block mask, set Coefficient source to Input port(s).
Connect vector signals to the Num and Den coefficient ports.

The following limitations apply to the HDL optimizations for a programmable Biquad Filter block:

Fully serial and partly serial architectures are not supported. Architecture must be set to Fully parallel.
Canonical signed digit (CSD) multiplier optimization is not supported. CoeffMultipliers must be set to multiplier.

Multichannel Filter Support

HDL Coder supports the use of vector inputs to Biquad Filter blocks.

Connect a vector signal to the Biquad Filter block input port.
Specify Input processing as Elements as channels (sample based).
To reduce area by sharing the filter kernel between channels, set the StreamingFactor parameter of the subsystem to the number of channels. See the Streaming section of Subsystem Optimizations for Filters (HDL Coder).

Serial Architectures

To use block-level optimizations to reduce hardware resources, select a serial Architecture. Then set either NumMultipliers or Folding Factor. See HDL Filter Properties.

When you select a serial architecture, set Filter structure to Direct form I or Direct form II. The direct form transposed structures are not supported with serial architectures.

AddPipelineRegisters Support

When you use AddPipelineRegisters, registers are placed based on the filter structure. The pipeline register placement determines the latency.

Filter Structure	Pipeline Register Placement	Latency (Clock Cycles)
Any	Pipeline registers are added between the filter sections.	`NS-1`, where `NS` is number of sections.

Subsystem Optimizations

This block can participate in subsystem-level optimizations such as sharing, streaming, and pipelining. For the block to participate in subsystem-level optimizations, set Architecture to Fully parallel. See Subsystem Optimizations for Filters (HDL Coder).

HDL Filter Properties

AddPipelineRegisters	Insert a pipeline register between stages of computation in a filter. See also AddPipelineRegisters (HDL Coder).
CoeffMultipliers	Specify the use of canonical signed digit (CSD) optimization to decrease filter area by replacing coefficient multipliers with shift-and-add logic. When you choose a fully parallel filter implementation, you can set CoeffMultipliers to `csd` or `factored-csd`. The default is `multipliers`, which retains multipliers in the HDL. See also CoeffMultipliers (HDL Coder).
FoldingFactor	Specify a serial implementation of an IIR SOS filter by the number of cycles it takes to generate the result. See also FoldingFactor (HDL Coder).
NumMultipliers	Specify a serial implementation of an IIR SOS filter by the number of hardware multipliers that are generated. See also NumMultipliers (HDL Coder).

For more details about HDL filter properties, see HDL Filter Block Properties (HDL Coder).

HDL Block Properties

ConstrainedOutputPipeline	Number of registers to place at the outputs by moving existing delays within your design. Distributed pipelining does not redistribute these registers. The default is `0`. For more details, see ConstrainedOutputPipeline (HDL Coder).
InputPipeline	Number of input pipeline stages to insert in the generated code. Distributed pipelining and constrained output pipelining can move these registers. The default is `0`. For more details, see InputPipeline (HDL Coder).
OutputPipeline	Number of output pipeline stages to insert in the generated code. Distributed pipelining and constrained output pipelining can move these registers. The default is `0`. For more details, see OutputPipeline (HDL Coder).

Restrictions

Frame input is not supported for HDL code generation.
You must set Initial conditions to 0. HDL code generation is not supported for nonzero initial states.
You must select Optimize unity scale values.
You cannot generate HDL for this block inside a Resettable Synchronous Subsystem (HDL Coder).

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

If the input is fixed point, it must be signed integer or signed fixed point with power-of-two slope and zero bias.

The diagrams in the following sections show the filter structures supported by the Biquad Filter block. They also show the data types used in the filter structures for fixed-point signals. You can set the data types shown in these diagrams in the block dialog box.

Direct Form I

The following diagram shows the data types for one section of the filter for fixed-point signals.

The following diagrams show the fixed-point data types between filter sections.

When the data is not optimized:

When you select Optimize unity scale values and scale values equal 1:

Direct Form I Transposed

The following diagram shows the data types for one section of the filter for fixed-point signals.

The dashed casts are omitted when Optimize unity scale values is selected and scale values equal one.

The following diagrams show the fixed-point data types between filter sections.

When the data is not optimized:

When you select Optimize unity scale values and scale values equal 1:

Direct Form II

The following diagram shows the data types for one section of the filter for fixed-point signals.

The dashed casts are omitted when Optimize unity scale values is selected and scale values equal one.

The following diagrams show the fixed-point data types between filter sections.

When the data is not optimized:

When you select Optimize unity scale values and scale values equal 1:

Direct Form II Transposed

The following diagram shows the data types for one section of the filter for fixed-point signals.

The following diagrams show the fixed-point data types between filter sections.

When the data is not optimized:

When you select Optimize unity scale values and scale values equal 1:

Documentation

Biquad Filter

Description

Ports

Input

In — Data input vector | matrix

Num — Numerator coefficients matrix

Dependencies

Den — Denominator coefficients matrix

Dependencies

g — Scale values row vector

Dependencies

Output

Out — Filtered output vector | matrix

Parameters

Main Tab

Coefficient source — Mode of operation Dialog parameters (default) | Input port(s) | Filter object

Filter — Name of filter object BQF (default) | dsp.BiquadFilter System object name

Dependencies

Filter structure — Filter structure Direct form II transposed (default) | Direct form I | Direct form I transposed | Direct form II

Dependencies

SOS Matrix (Mx6) — SOS matrix [1 0.3 0.4 1 0.1 0.2] (default) | M-by-6 matrix

Dependencies

Scale values — Scale values 1 (default) | scalar | vector

Dependencies

Initial conditions — Initial conditions 0 (default) | scalar | vector

Dependencies

Initial conditions on zeros side — Initial conditions on zeros side 0 (default) | scalar | vector

Dependencies

Initial conditions on poles side — Initial conditions on poles side 0 (default) | scalar | vector

Dependencies

Scale values mode — Mode to specify scale values Specify via input port (g) (default) | Assume all are unity and optimize

Dependencies

Action when the a0 values of the SOS matrix are not one — Action when a0 values of SOS matrix are not one Warning (default) | None | Error

Dependencies

Optimize unity scale values — Optimize unity scale values on (default) | off

Dependencies

Input processing — Input processing Columns as channels (frame based) (default) | Elements as channels (sample based)

View Filter Response — View filter response button

Data Types Tab

Rounding mode — Rounding mode Floor (default) | Ceiling | Convergent | Nearest | Round | Simplest | Zero

Saturate on integer overflow — Method of overflow action off (default) | on

Section input — Section input data type Same as input (default) | Binary point scaling

Section output — Section output data type Same as section input (default) | Binary point scaling

Multiplicand — Multiplicand data type Same as output (default) | Binary point scaling

Dependencies

Coefficients — Coefficients data type Same word length as input (default) | Specify word length | Binary point scaling

Dependencies

Product output — Product output data type Same as input (default) | Inherit via internal rule | Binary point scaling

Accumulator — Accumulator data type Same as product output (default) | Same as input | Binary point scaling

States — States data type Same as accumulator (default) | Same as input | Binary point scaling

Dependencies

Output — Output data type Same as accumulator (default) | Same as input | Binary point scaling

Lock data type settings against changes by the fixed-point tools — Lock data type settings off (default) | on

Model Examples

Code Generation for Parametric Audio Equalizer

Group Delay Estimation

Parametric Audio Equalizer

Block Characteristics

Extended Capabilities

C/C++ Code Generation Generate C and C++ code using Simulink® Coder™.

HDL Code Generation Generate Verilog and VHDL code for FPGA and ASIC designs using HDL Coder™.

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

See Also

Objects

Blocks

DSP System Toolbox Documentation

Support

`In` — Data input
vector | matrix

`Num` — Numerator coefficients
matrix

`Den` — Denominator coefficients
matrix

`g` — Scale values
row vector

`Out` — Filtered output
vector | matrix

`Coefficient source` — Mode of operation
`Dialog parameters` (default) | `Input port(s)` | `Filter object`

`Filter` — Name of filter object
`BQF` (default) | `dsp.BiquadFilter System object` name

`Filter structure` — Filter structure
`Direct form II transposed` (default) | `Direct form I` | `Direct form I transposed` | `Direct form II`

`SOS Matrix (Mx6)` — SOS matrix
`[1 0.3 0.4 1 0.1 0.2]` (default) | M-by-6 matrix

`Scale values` — Scale values
`1` (default) | scalar | vector

`Initial conditions` — Initial conditions
`0` (default) | scalar | vector

`Initial conditions on zeros side` — Initial conditions on zeros side
`0` (default) | scalar | vector

`Initial conditions on poles side` — Initial conditions on poles side
`0` (default) | scalar | vector

`Scale values mode` — Mode to specify scale values
`Specify via input port (g)` (default) | `Assume all are unity and optimize`

`Action when the a0 values of the SOS matrix are not one` — Action when a0 values of SOS matrix are not one
`Warning` (default) | `None` | `Error`

`Optimize unity scale values` — Optimize unity scale values
`on` (default) | `off`

`Input processing` — Input processing
`Columns as channels (frame based)` (default) | `Elements as channels (sample based)`

`View Filter Response` — View filter response
button

`Rounding mode` — Rounding mode
`Floor` (default) | `Ceiling` | `Convergent` | `Nearest` | `Round` | `Simplest` | `Zero`

`Saturate on integer overflow` — Method of overflow action
`off` (default) | `on`

`Section input` — Section input data type
`Same as input` (default) | `Binary point scaling`

`Section output` — Section output data type
`Same as section input` (default) | `Binary point scaling`

`Multiplicand` — Multiplicand data type
`Same as output` (default) | `Binary point scaling`

`Coefficients` — Coefficients data type
`Same word length as input` (default) | `Specify word length` | `Binary point scaling`

`Product output` — Product output data type
`Same as input` (default) | `Inherit via internal rule` | `Binary point scaling`

`Accumulator` — Accumulator data type
`Same as product output` (default) | `Same as input` | `Binary point scaling`

`States` — States data type
`Same as accumulator` (default) | `Same as input` | `Binary point scaling`

`Output` — Output data type
`Same as accumulator` (default) | `Same as input` | `Binary point scaling`

`Lock data type settings against changes by the fixed-point tools` — Lock data type settings
`off` (default) | `on`

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