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Sample rate Converter

Started by arun naik ●October 19, 2000
Hello Friends!
I would like to know about the performance of Polyphase filter implementation for Sample Rate Conversion(SRC).
 
I tried developing a SRC for Upsamper = 3 and Down Sampler = 2.
 
I find that filter implemented in Polyphase has additional tonal components 25dB down wrt the input tonal component at higher ends.
 
Apparently these are images(due to upsampling) of the input tonal component.
 
But the filter implemented should have attenuated these components by 136dB(according to Filter Design).
 
I have checked the response of the filter by applying tonal components at the input of the filter(not at upsampler input) and checking it out at its o/p. The filter doesn't have any problems.
 
So, now I have a doubt.
 
Either my implementation of the Polyphase filter is wrong 
or
the performance of polyphase Filter is not very good though it gives computational advantage.
(I have done the implementation on C.)
 
Can any one throw some light on this? Your help will be greatly appreciated.
Please feel free to suggest your ideas and guesses.
 
Thanks in advance.
regards
arun