Abstract:

To remove the noise interference in NMR (Nuclear Magnetic Resonance) signal,espe
cially the industrial frequency harmonics noise interference near larmor frequen
cy,the noise removal method based on adaptive filter was researched.Based
on introducing the basic principles of adaptive noise filtering,the simulation p
erformance of adaptive notch filter was studied.And the method was appli
ed to removing the industrial frequency harmonics noise interference of the actu
al NMR signal.The study shows that compared with the traditional notch filter,ad
aptive notch filter can automatically track the frequency and phase of the inter
ference,and that it also brings small distortion and 5% of high precision of the
 amplitude  error and relaxation time error after the envelope fitting for
the signal filtered.So the adaptive notch filter can effectively remove the
industrial frequency harmonics interference.

Key words: nuclear magnetic resonance (NMR), interference elimination, adaptive filter, indust
rial frequency harmonics