decimation interpolation

[naresh850]

hi,
any one can help me on difference between decimation & downsampling
why there is a need of filter in decimation & interpolation.
before filter in decimation & after filter in interpolation.

 

[mohanlal]

decimation is nothing but decreasing the samples/sec and accordingly shifting the freq spectrum towards DC.
interpolation is adding more sampling points in between the the samples of interest. Filtering is required to curb the outgoing spectral components.
this is very brief answer ,i thing.

 

[naresh850]

sir,

i still confuse about filter requirment

regards

 

[starfish]

Decimation is the process of throwing away redundant samples from your signal. If decimation is by a factor of '2' then this means that throw away every other sample in ur signal.

Similarly Interpolation is the process of increasing the sampling rate by some factor. If interpolation is by a factor of 2 then this means that after every sample add another sample. There are many types of interpolators like Linear , Triangualar , but Sinc is and ideal interpolator.

In decimation u must pass ur signal through an Antialiasing filter and then throw away samples. Remember u should keep twice the number of samples than ur max frequency content present in the signal.

In interpolation first u insert zeros b/w consecutive samples and then pass it through a Low Pass filter which reconstructs the intermediate values and hence is equivalent as if it was sampled at a higher rate.

 

[naresh850]

thanks Starfish!!!