The first frequency line in the power spectrum always represents DC (frequency=0). The last frequency line can be found at fSAMPLE/2 - fSAMPLE/NRECORD. Frequency lines are spaced at even intervals of fSAMPLE/NRECORD. They are commonly referred to as frequency bins or FFT bins. Bins can also be computed with reference to a data converter's sampling period:
Bin = fSAMPLE/NRECORD = 1/(NRECORD × ΔtSAMPLE)Example: We apply a sampling frequency of 82MHz and take 8192 records. The frequency bin is 10kHz.