High-power active interference suppression in magnetic particle imaging

Fig. 2 shows the frequency spectra for the received MPI signal before and after active cancellation of distortion interference. With cancellation, interference at frequencies from the 2nd to the 8th harmonic was suppressed below the system noise floor, with 2nd harmonic interference decreasing 45 dB. Interestingly, 60 Hz side lobes from intermodulation distortion products near the interfering frequencies were not attenuated by active cancellation, suggesting that intermodulation mixing occurs before active cancellation in the main transmit chain.