An FFT is to be used to determine the dominant frequency of a repeating signal t
ID: 3280058 • Letter: A
Question
An FFT is to be used to determine the dominant frequency of a repeating signal that is expected to be near 250 Hz. What is the minimum sampling rate that should be used to investigate the frequency characteristics of the signal? If the signal is sampled at a rate of 1500 samples per second, how many samples should be acquired to achieve a resolution of 0.5 Hz in the FFT results? At 1500 samples per second, for how long must the signal be sampled to achieve a resolution of 0.5 Hz in the FFT results?
Explanation / Answer
a)
Minimum sampling rate
fs=2fmax=2*250
fs=500 Hz
b)
frequency resolution is given by
df=fs/N
N=1500/0.5=3000 samples
c)
T=N/fs=3000/1500
T= 2 sec