Filter Design Toolbox

mfilt.linearinterp

Construct a linear interpolator filter object

Syntax

• hm = mfilt.linearinterp(l) 
  

Description

hm = mfilt.linearinterp(l) returns an FIR linear interpolator hm with an integer interpolation factor l. l must be an integer. The default value for l is 2 when you do not include the input argument l.

Input Arguments

Entries in the following table describe the input arguments for mfilt.linearinterp.

Input Argument	Description
l	Interpolation factor for the filter. l specifies the amount to increase the input sampling rate. It must be an integer. When you do not specify a value for l it defaults to 2.

mfilt.linearinterp Object Properties

Every multirate filter object has properties that govern the way it behaves when you use it. Note that many of the properties are also input arguments for creating mfilt.linearinterp objects.The next table describes each property for an mfilt.linearinterp filter object.

Name	Values	Description
FilterStructure	String	Reports the type of filter object, such as a decimator or fractional integrator. You cannot set this property--it is always read only and results from your choice of mfilt object.
InterpolationFactor	Integer	Interpolation factor for the filter. l specifies the amount to increase the input sampling rate. It must be an integer.
NonProcessedSamples	0	Shows the values of the samples that were not processed during the filtering operation. Note that this is not the number of samples that were not processed.
ResetBeforeFiltering	'off' or 'on'	Determine whether the filter states get restored to zero for each filtering operation
States	Double array	Filter states. states defaults to a vector of zeros that has length equal to nstates(hm)
NumSamplesProcessed	Integer	Returns the number of samples processed during filtering. As a check, the number of samples reported processed plus the number of nonprocessed samples should be the total number of input samples.

Examples

Interpolation by a factor of 2 (used to convert the input signal sampling rate from 22.05 KHz to 44.1 KHz).

• l = 2;                      % Interpolation factor
  hm = mfilt.linearinterp(l);
  fs = 22.05e3;               % Original sampling frequency: 22.05 KHz
  n = 0:5119;                 % 5120 samples, 0.232 second long signal
  x  = sin(2*pi*1e3/fs*n);    % Original signal, sinusoid at 1 KHz
  y = filter(hm,x);           % 10240 samples, still 0.232 seconds
  stem(n(1:22)/fs,x(1:22),'filled') % Plot original sampled at 
                                    % 22.05 KHz 
  hold on                     % Plot interpolated signal (44.1 
                              % KHz) in red
  stem(n(1:44)/(fs*l),y(2:45),'r')
  xlabel('Time (sec)');ylabel('Signal Value')
  

See Also

mfilt.holdinterp, mfilt.firinterp, mfilt.firfracinterp, mfilt.cicinterp, mfilt.cicinterpzerolat

mfilt.holdinterp

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