LTPDA Toolbox™

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Downsampling data

Description

Downsampling is the process of reducing the sampling rate of a signal. Downsample reduces the sampling rate of the input AOs by an integer factor by picking up one out of N samples. Note that no anti-aliasing filter is applied to the original data. Moreover, a offset can be specified, i.e., the sample at which the output data starts ---see examples below.

Syntax

    

    b = downsample(a, pl)
  

Parameters

The following parameters can be set in this method:

• factor - decimation factor [by default is 1: no downsampling] (must be an integer)
• offset - sample offset for decimation

Examples

1. Downsampling a sequence of random data at original sampling rate of 10 Hz by a factor of 4 (fsout = 2.5 Hz) and no offset.

    

    % create an AO of random data with fs = 10 Hz
    pl      = plist('tsfcn', 'randn(size(t))','fs',10,'nsecs',10,'yunits','m');
    x       = ao(pl)
    pl_down = plist('factor', 4);     % add the decimation factor
    y       = downsample(x, pl_down); % downsample the input AO, x
    iplot(x, y)
  

2. Downsampling a sequence of random data at original sampling rate of 10 Hz by a factor of 4 (fsout = 2.5 Hz) and offset = 10.

    

    % create an AO of random data with fs = 10 Hz
    pl         = plist('tsfcn', 'randn(size(t))','fs',10,'nsecs',10,'yunits','m');
    x          = ao(pl)
    pl_downoff = plist('factor', 4,'offset',10);  % add the decimation factor and the offset parameter
    y          = downsample(x, pl_downoff);       % downsample the input AO, x
    iplot(x, y)
  

Signal Pre-processing in LTPDA

Upsampling data

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