Decimation Low Pass Filter

[Eminent.Engineer]

Hello Everyone

Would like to know about very basic concept regarding Decimation Process, Let my baseband signal is 1KHZ and it is sampled at very high sampling rate let say 650KHz now I want to downsample the signal to decrease sampling frequency to Nyquist criteria, so what should be the cut off frequency of anti-aliasing Low Pass Fiter ?
So Max. Input Frequency = 1KHz
Sampling Frequency = 650 KHz
Nyquist Criteria >= 2KHz
Downsampling to get 2.5 KHz sampling frequency.

Thanks in Advance.

 

[Mityan]

so what should be the cut off frequency of anti-aliasing Low Pass Fiter ?

Do you use MAtLAB?
If yes, just type "fdatool" in command line.
Then in the opened window of FDATool set the parameters:
Fs = 2500
For Fpass and Fstop you may choose any value between 1000 and Fs/2. But Fpass<Fstop.
Try several combinations and choose one you like most.
This just a question of memory for filter taps and computational resources you may allow to yourself.
I think no other reasonable limitations.

 

[Pulkit Varshney]

there will be no aliasing in this case, as your data is given.

 

[FvM]

there will be no aliasing in this case, as your data is given

There will be aliasing, depending on level of off-band interferences and the stop band attenuation of the decimation filter. That's what e.g. fdatool calculates.

 

[Pulkit Varshney]

you are right FvM...
i was considering the ideal case ..i.e. no off band interferences and ideal filter, in that case aliasing would only because of frequency spread because of down sampling.