parallel

Create parallel sum filter structure

Syntax

PF = parallel(branch1,branch2,...,branchn)

PF = parallel(___,InputSampleRate=Value)

Description

PF = parallel(branch1,branch2,...,branchn) returns an object PF of type dsp.ParallelFilter. PF is a parallel structure of the filter branches branch1, branch2, ..., branchn. Each individual branch can be a filter System object™ or a scalar gain value, but at least one branch must be a filter object.

The input filter objects must be supported by the parallel function. To see a list of filter objects that you can add as branches to the parallel filter stack, run this command in the MATLAB^® command prompt.

dsp.ParallelFilter.helpSupportedSystemObjects

PF = parallel(___,InputSampleRate=Value) specifies the input sample rate of the parallel filter as one of these options:

• Positive real scalar — The input sample rate of the parallel filter is a positive real scalar.

• "normalized" — The input sample rate of the parallel filter is in normalized frequency units regardless of the input sample rate of the individual filter branches.

• "auto" — The input sample rate of the parallel filter is determined from the input sample rate of the individual filter branches as per these conditions:

  • If all the branches have a normalized frequency, then the parallel filter has a normalized frequency.

  • If more than one branch has an absolute sample rate, then the sample rate of these branches must be consistent with the rate conversion ratio of the segment connecting them. The sample rate of the overall parallel filter is in absolute units.

  • If at least one branch has an absolute sample rate, then the sample rate of the overall parallel filter is in absolute units.

(since R2026a)

Examples

Construct Parallel Filter

You can construct a parallel filter using the dsp.ParallelFilter object or the parallel function.

First, create the branches.

B1 = dsp.FIRFilter;
B2 = dsp.Delay(3);
B3 = 2;

Specify these branches while constructing the dsp.ParallelFilter object.

pf1 = dsp.ParallelFilter(B1,B2,B3)

pf1 = 
  dsp.ParallelFilter with properties:

          Branch1: [1×1 dsp.FIRFilter]
          Branch2: [1×1 dsp.Delay]
          Branch3: 2
    CloneBranches: true

You can also use the addBranch function to add branches to the default parallel filter.

pf2 = dsp.ParallelFilter(B1);
addBranch(pf2,B2,B3);
pf2

pf2 = 
  dsp.ParallelFilter with properties:

          Branch1: [1×1 dsp.FIRFilter]
          Branch2: [1×1 dsp.Delay]
    CloneBranches: true

Now, use the parallel filter function to construct a dsp.ParallelFilter object.

pf3 = parallel(B1,B2,B3)

pf3 = 
  dsp.ParallelFilter with properties:

          Branch1: [1×1 dsp.FIRFilter]
          Branch2: [1×1 dsp.Delay]
          Branch3: 2
    CloneBranches: true

Specify Input Sample Rate in dsp.ParallelFilter Object

Since R2026a

Specify the input sample rate explicitly while constructing the dsp.ParallelFilter object using the InputSampleRate argument.

Parallel Filter with Absolute Sample Rate

Create a dsp.ParallelFilter object with three branches. Each branch is a dsp.FIRFilter object operating in normalized frequency units. Specify the sample rate of the parallel filter as 22050 Hz using the InputSampleRate argument.

filtNorm1 = dsp.FIRFilter;
firtNorm2 = dsp.FIRFilter(designLowpassFIR(FilterOrder=30,CutoffFrequency=0.5,Window="hann"));
filtNorm3 = dsp.FIRFilter(designLowpassFIR(FilterOrder=10,CutoffFrequency=0.5));
parallelSpecifySampleRate = parallel(filtNorm1,firtNorm2,filtNorm3,InputSampleRate=22050)

parallelSpecifySampleRate = 
  dsp.ParallelFilter with properties:

          Branch1: [1×1 dsp.FIRFilter]
          Branch2: [1×1 dsp.FIRFilter]
          Branch3: [1×1 dsp.FIRFilter]
    CloneBranches: true

The parallel filter operates at the absolute frequency that you specify regardless of the sample rate of the filter branches.

info(parallelSpecifySampleRate)

ans = 
    'Discrete-Time Filter Parallel Filter
     ----------------------------
     Number of branches: 3
     Branch cloning: enabled
     Input sample rate: 22050
     ----------------------------
     
     Branch1: dsp.FIRFilter
     -------
     Discrete-Time FIR Filter (real)    
     -------------------------------    
     Filter Structure  : Direct-Form FIR
     Filter Length     : 2              
     Stable            : Yes            
     Linear Phase      : Yes (Type 2)   
     Input sample rate : Normalized     
     
     
     Branch2: dsp.FIRFilter
     -------
     Discrete-Time FIR Filter (real)    
     -------------------------------    
     Filter Structure  : Direct-Form FIR
     Filter Length     : 31             
     Stable            : Yes            
     Linear Phase      : Yes (Type 1)   
     Input sample rate : Normalized     
     
     
     Branch3: dsp.FIRFilter
     -------
     Discrete-Time FIR Filter (real)    
     -------------------------------    
     Filter Structure  : Direct-Form FIR
     Filter Length     : 11             
     Stable            : Yes            
     Linear Phase      : Yes (Type 1)   
     Input sample rate : Normalized     
     
     '

Parallel Filter with Normalized Sample Rate

Specify normalized sample rate on the cascade. The first branch of the filter cascade has a sample rate of 17 Hz. The remaining filter branches operate in normalized frequency units.

filtAbs1 = dsp.FIRFilter(SampleRate=17);
firtNorm2 = dsp.FIRFilter(designLowpassFIR(FilterOrder=30,CutoffFrequency=0.5,Window="hann"));
filtNorm3 = dsp.FIRFilter(designLowpassFIR(FilterOrder=10,CutoffFrequency=0.5));
parallelNormSampleRate = parallel(filtAbs1,firtNorm2,filtNorm3,InputSampleRate="normalized")

parallelNormSampleRate = 
  dsp.ParallelFilter with properties:

          Branch1: [1×1 dsp.FIRFilter]
          Branch2: [1×1 dsp.FIRFilter]
          Branch3: [1×1 dsp.FIRFilter]
    CloneBranches: true

The parallel filter operates in normalized frequency units regardless of the sample rate of the individual filter branches.

info(parallelNormSampleRate)

ans = 
    'Discrete-Time Filter Parallel Filter
     ----------------------------
     Number of branches: 3
     Branch cloning: enabled
     Input sample rate: Normalized
     ----------------------------
     
     Branch1: dsp.FIRFilter
     -------
     Discrete-Time FIR Filter (real)    
     -------------------------------    
     Filter Structure  : Direct-Form FIR
     Filter Length     : 2              
     Stable            : Yes            
     Linear Phase      : Yes (Type 2)   
     Input sample rate : 17             
     
     
     Branch2: dsp.FIRFilter
     -------
     Discrete-Time FIR Filter (real)    
     -------------------------------    
     Filter Structure  : Direct-Form FIR
     Filter Length     : 31             
     Stable            : Yes            
     Linear Phase      : Yes (Type 1)   
     Input sample rate : Normalized     
     
     
     Branch3: dsp.FIRFilter
     -------
     Discrete-Time FIR Filter (real)    
     -------------------------------    
     Filter Structure  : Direct-Form FIR
     Filter Length     : 11             
     Stable            : Yes            
     Linear Phase      : Yes (Type 1)   
     Input sample rate : Normalized     
     
     '

Parallel Filter with Auto Sample Rate

Set the input sample rate of the parallel filter to "auto". The individual filters have a combination of normalized and absolute sample rates. The parallel filter uses the absolute sample rate.

filtAbs1 = dsp.FIRFilter(SampleRate=17);
firtNorm2 = dsp.FIRFilter(designLowpassFIR(FilterOrder=30,CutoffFrequency=0.5,Window="hann"));
filtAbs2 = dsp.FIRFilter(designLowpassFIR(FilterOrder=10,CutoffFrequency=0.5),SampleRate=17);
parallelAutoSampleRate = parallel(filtAbs1,firtNorm2,filtAbs2,InputSampleRate="auto");
info(parallelAutoSampleRate)

ans = 
    'Discrete-Time Filter Parallel Filter
     ----------------------------
     Number of branches: 3
     Branch cloning: enabled
     Input sample rate: 17
     ----------------------------
     
     Branch1: dsp.FIRFilter
     -------
     Discrete-Time FIR Filter (real)    
     -------------------------------    
     Filter Structure  : Direct-Form FIR
     Filter Length     : 2              
     Stable            : Yes            
     Linear Phase      : Yes (Type 2)   
     Input sample rate : 17             
     
     
     Branch2: dsp.FIRFilter
     -------
     Discrete-Time FIR Filter (real)    
     -------------------------------    
     Filter Structure  : Direct-Form FIR
     Filter Length     : 31             
     Stable            : Yes            
     Linear Phase      : Yes (Type 1)   
     Input sample rate : Normalized     
     
     
     Branch3: dsp.FIRFilter
     -------
     Discrete-Time FIR Filter (real)    
     -------------------------------    
     Filter Structure  : Direct-Form FIR
     Filter Length     : 11             
     Stable            : Yes            
     Linear Phase      : Yes (Type 1)   
     Input sample rate : 17             
     
     '

The input sample rate of the parallel filter is set to "auto". The sample rate of the FIR filter and FIR interpolator is in absolute units. Since there is a rate conversion ratio of 3 between the two branches, the sample rate of these branches must be consistent with this rate conversion ratio. The input sample rate of the overall parallel filter is 22050 Hz.

filtNorm1 = dsp.FIRFilter(SampleRate=22050);
filtNorm4 = dsp.FIRDecimator(3);  % Normalized frequency
filtAbs3 = dsp.FIRInterpolator(InputSampleRate=22050/3);
parallelAutoSampleRate2 = cascade(filtNorm1,filtNorm4,filtAbs3,InputSampleRate="auto");
info(parallelAutoSampleRate2)

ans = 
    'Discrete-Time Filter Cascade
     ----------------------------
     Number of stages: 3
     Stage cloning: enabled
     Input sample rate: 22050
     ----------------------------
     
     Stage1: dsp.FIRFilter
     -------
     Discrete-Time FIR Filter (real)    
     -------------------------------    
     Filter Structure  : Direct-Form FIR
     Filter Length     : 2              
     Stable            : Yes            
     Linear Phase      : Yes (Type 2)   
     Input sample rate : 22050          
     
     
     Stage2: dsp.FIRDecimator
     -------
     Discrete-Time FIR Multirate Filter (real)               
     -----------------------------------------               
     Filter Structure   : Direct-Form FIR Polyphase Decimator
     Decimation Factor  : 3                                  
     Polyphase Length   : 24                                 
     Filter Length      : 72                                 
     Stable             : Yes                                
     Linear Phase       : Yes (Type 1)                       
                                                             
     Arithmetic         : double                             
     Input sample rate : Normalized                          
     
     
     Stage3: dsp.FIRInterpolator
     -------
     Discrete-Time FIR Multirate Filter (real)                     
     -----------------------------------------                     
     Filter Structure      : Direct-Form FIR Polyphase Interpolator
     Interpolation Factor  : 3                                     
     Polyphase Length      : 24                                    
     Filter Length         : 72                                    
     Stable                : Yes                                   
     Linear Phase          : Yes (Type 1)                          
                                                                   
     Arithmetic            : double                                
     Input sample rate : 7350                                      
     
     '

Consider a parallel filter with nested branches. The input sample rate of the first parallel filter is 22050 Hz. The input sample rate of the second parallel filter is "normalized".

Create a parallel filter with these two filter structures as branches and set the input sample rate of the overall parallel filter to "auto".

filtParallelSpecifySampleRate = dsp.ParallelFilter(InputSampleRate=22050)

filtParallelSpecifySampleRate = 
  dsp.ParallelFilter with properties:

          Branch1: [1×1 dsp.FIRFilter]
    CloneBranches: true

filtParallelNormSampleRate = dsp.ParallelFilter(InputSampleRate="normalized")

filtParallelNormSampleRate = 
  dsp.ParallelFilter with properties:

          Branch1: [1×1 dsp.FIRFilter]
    CloneBranches: true

filtNestedParallel = parallel(filtParallelSpecifySampleRate,filtParallelNormSampleRate,InputSampleRate="auto")

filtNestedParallel = 
  dsp.ParallelFilter with properties:

          Branch1: [1×1 dsp.ParallelFilter]
          Branch2: [1×1 dsp.ParallelFilter]
    CloneBranches: true

The first parallel filter has an absolute sample rate and the second parallel filter operates in normalized frequency units. The nested parallel filter in the "auto" configuration uses the absolute sample rate.

info(filtNestedParallel)

ans = 
    'Discrete-Time Filter Parallel Filter
     ----------------------------
     Number of branches: 2
     Branch cloning: enabled
     Input sample rate: Normalized
     ----------------------------
     
     Branch1: dsp.ParallelFilter
     -------
     Discrete-Time Filter Parallel Filter
     ----------------------------
     Number of branches: 1
     Branch cloning: enabled
     Input sample rate: 22050
     ----------------------------
     
     Branch1: dsp.FIRFilter
     -------
     Discrete-Time FIR Filter (real)    
     -------------------------------    
     Filter Structure  : Direct-Form FIR
     Filter Length     : 2              
     Stable            : Yes            
     Linear Phase      : Yes (Type 2)   
     Input sample rate : Normalized     
     
     
     
     
     Branch2: dsp.ParallelFilter
     -------
     Discrete-Time Filter Parallel Filter
     ----------------------------
     Number of branches: 1
     Branch cloning: enabled
     Input sample rate: Normalized
     ----------------------------
     
     Branch1: dsp.FIRFilter
     -------
     Discrete-Time FIR Filter (real)    
     -------------------------------    
     Filter Structure  : Direct-Form FIR
     Filter Length     : 2              
     Stable            : Yes            
     Linear Phase      : Yes (Type 2)   
     Input sample rate : Normalized     
     
     
     
     '

Input Arguments

branch — Filter branch

filter System object | scalar

Filter branch, specified as a filter System object or a scalar gain value. The parallel function does not create a dsp.ParallelFilter object when all input branches are scalar values. At least one branch in the structure must be a filter object.

To see a list of filter objects that you can add as branches to the parallel filter stack, run this command in the MATLAB command prompt.

dsp.ParallelFilter.helpSupportedSystemObjects

InputSampleRate — Input sample rate of filter cascade

scalar | "normalized" | "auto"

Since R2026a

Input sample rate of the parallel filter, specified as one of these:

• Positive real scalar — The input sample rate of the parallel filter is a positive real scalar.

• "normalized" — The input sample rate of the parallel filter is in normalized frequency units regardless of the input sample rate of the individual filter branches.

• "auto" — The input sample rate of the parallel filter is determined from the input sample rate of the individual filter branches as per these conditions:

  • If all the branches have a normalized frequency, then the parallel filter has a normalized frequency.

  • If more than one branch has an absolute sample rate, then the sample rate of these branches must be consistent with the rate conversion ratio of the segment connecting them. The sample rate of the overall parallel filter is in absolute units.

  • If at least one branch has an absolute sample rate, then the sample rate of the overall parallel filter is in absolute units.

Data Types: single | double | char | string

Output Arguments

PF — Parallel filter

dsp.ParallelFilter System object

Parallel filter, returned as a System object of type dsp.ParallelFilter. For information on the properties of the filter in each branch, type info(PF) in the MATLAB command prompt.

Version History

Introduced before R2006a

R2026a: Input sample rate specification enhancements

Using the InputSampleRate argument, you can now specify the input sample rate explicitly while constructing the dsp.ParallelFilter object using the parallel function.

To specify the input sample rate after constructing the object, use the setInputSampleRate function.

You can view the sample rate information using the Input sample rate field of the info function.

R2023b: Support for dsp.ParallelFilter Object

Starting in R2023b, the parallel analysis function generates a dsp.ParallelFilter object.