Filter Design Toolbox™

dfilt.allpass - Allpass filter

Syntax

hd = dfilt.allpass(c)

Description

hd = dfilt.allpass(c) constructs an allpass filter with the minimum number of multipliers from the elements in vector c. To be valid, c must contain one, two, three, or four real elements. The number of elements in c determines the order of the filter. For example, c with two elements creates a second-order filter and c with four elements creates a fourth-order filter.

The transfer function for the allpass filter is defined by

given the coefficients in c.

To construct a cascade of allpass filter objects, use dfilt.cascadeallpass. For more information about creating cascades of allpass filters, refer to dfilt.cascadeallpass.

Properties

The following table provides a list of all the properties associated with an allpass dfilt object.

Property Name	Brief Description
`AllpassCoefficients`	Contains the coefficients for the allpass filter object
`FilterStructure`	Describes the signal flow for the filter object, including all of the active elements that perform operations during filtering — gains, delays, sums, products, and input/output.
`PersistentMemory`	Specifies whether to reset the filter states and memory before each filtering operation. Lets you decide whether your filter retains states from previous filtering runs. `False` is the default setting.
`States`	This property contains the filter states before, during, and after filter operations. States act as filter memory between filtering runs or sessions. They also provide linkage between the sections of a multisection filter, such as a cascade filter. For details, refer to `filtstates` in Signal Processing Toolbox™ documentation or in the Help system.

Examples

This example constructs and displays the information about a second-order allpass filter that uses the minimum number of multipliers.

c = [1.5, 0.7];
% Create a second-order dfilt object.
hd = dfilt.allpass(c) 
hd =
 
        FilterStructure: 'Minimum-Multiplier Allpass'
    AllpassCoefficients: [1.5 0.7]                   
       PersistentMemory: false                       
                 States: [0;0;0;0]                   

info(hd) % Gets information about the filter.
Discrete-Time IIR Filter (real)                    
-------------------------------                    
Filter Structure       : Minimum-Multiplier Allpass
Number of Multipliers  : 2                         
Stable                 : Yes                       
Linear Phase           : No                        
                                                   
Implementation Cost                                
Number of Multipliers : 2                          
Number of Adders      : 4                          
Number of States      : 4                          
MultPerInputSample    : 2                          
AddPerInputSample     : 4

dfilt.allpass - Allpass filter

Syntax

Description

Properties

Examples

See Also