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What is the need of low pass filter prior to downsampling?
You need to apply a lowpass filter before you downsample the signal to avoid “aliasing”. The cutoff frequency of the lowpass filter should be less than the nyquist frequency, which is half the sample frequency.
Is decimation a low pass filter?
Both the interpolation and decimation filters incorporate a low-pass filtering function. The reason for this LPF, however, is quite different for each case. For decimation, the LPF serves to eliminate high frequency components in the spectrum.
What is the difference between decimation and downsampling?
Loosely speaking, “decimation” is the process of reducing the sampling rate. In practice, this usually implies lowpass-filtering a signal, then throwing away some of its samples. “Downsampling” is a more specific term which refers to just the process of throwing away samples, without the lowpass filtering operation.
Which is the best filter to use for decimation?
To implement the filtering part, you can use either FIR or IIR filters. To implement the downsampling part (by a downsampling factor of “M”) simply keep every Mth sample, and throw away the M-1 samples in between. For example, to decimate by 4, keep every fourth sample, and throw three out of every four samples away.
When to use decimation before or after downsampling?
However, since the original signal has components up to 10 kHz, you must lowpass-filter the signal prior to downsampling to remove all components above 5 kHz so that no aliasing will occur when downsampling. This combined operation of filtering and downsampling is called decimation.
How do you filter a signal before downsampling?
Create a signal with baseband spectral support greater than radians. Use decimate to filter the signal with a 10th-order Chebyshev type I lowpass filter prior to downsampling. Create the signal and plot the magnitude spectrum.
Can You downsample and decimate the same signal?
You can use decimate or resample to filter and downsample with one function. Alternatively, you can lowpass filter your data and then use downsample. Create a signal with baseband spectral support greater than π radians. Use decimate to filter the signal with a 10th-order Chebyshev type I lowpass filter prior to downsampling.