# Sampling frequency and its many manifestations for DSP manipulations.

Further to an earlier post on various frequencies and rates in a sampled DSP system or circuit, here is small addition to the collection. We know that if fs is the sampling rate, or sampling frequency, we can use it to normalize other frequencies in the circuit or system, by dividing the other frequencies by fs ( or fs/2) which is the normalizing factor. So we can use fs as unity ( fs/fs =1) and use this metric to normalize all other frequencies. We can also choose to use fs/2 as the normalizing factor so fs would be 2 in this case. MATLAB prefers to use fs/2 as the normalizing factor, so a 1 is fs/2 in this case.

We can also use another normalized expression for the frequency or frequencies. Divide the frequency in question by the sampling frequency and equate this to wo/2*pi. ( I like to think of wo as the radian frequency). The frequency in question ( say fo) should be expressed in terms of fs. So now you can express normalized frequencies in terms of pi!. All these units are very much in use in the DSP world. Please visit the Signal Processing Group Inc. website for more technical information.

I also like the treatment of digital frequency from two sources. Professor Fowler expose’ and from AllSignals, a website that appears to be very useful all around. I think anyone desirous of entering or remaining in the field of DSP should be very aware of the concept. Please visit our website for more info about us and technical info.