Type of active impulse noise suppressing method based on double‐loop antennas in very low frequency/ultra‐low frequency coupling communications

Abstract

Very low frequency/ultra-low frequency coupling communication systems suffer from severe disturbance from non-Gaussian impulsive noises which producing significant long tails. Considering the significant in-band parts of the impulse, traditional noise-suppression methods are not adequate in improving the signal-to-noise ratio (SNR), and the performance of existing dipole–loop double antennas active noise suppression systems are limited to a low level due to the different directionality of the antennas. A new double-loop antennas active noise suppressing system was proposed, in which one multi-turn loop antenna was employed to receive the useful signals, and one single-turn loop was employed as the noise reference antenna. A mathematical morphology processor and a time-switch filter were employed to extract the impulsive noise, and the digital equivalent model of the multi-turn loop antenna was established filtering the extracted impulsive noise to obtain a duplicate transient, which is highly correlated with the transients received from the multi-turn loop antenna. The system SNR was improved by subtracting the transient duplicate from the received signals. Simulations were carried out with Monte Carlo method, showing that the SNR can be improved with the gain of about 18 dB with communication error rate extremely reduced by orders of magnitude. Experiment system was also designed and established to verify the feasibility and efficiency, and a 50 m communication experiment in an industrial environment showed that the error rate can be decreased from 0.2 to 0.06% while employing the proposed noise suppression method.