Ok I have an odd question. I am sampling a 50Hz signal on a microchip at a sampling frequency of 600Hz. I need to include an antialiasing filter in the circuit, but my question is with the filter design. I am going with a simple resistor and capacitor design, but what is the frequency that i will use to design the filter. The equation is fcutoff = 1/(2piRC). Is the cut off frequency based on the signal being sampled, the sampling frequency, or both? Thank You

 

If the sampling frequency is 600Hz then the maximum signals frequency before alising occurs is 300Hz. A cut off frequency of 150 Hz will be fine because it won't attenuate the 50 Hz signal and frequencies above 300 Hz will be attenuated sufficiently (of course this depends on the filter characterirstics).