Abstract: A control method and system for filtering power line interference is disclosed. The control method includes the following steps. First, ECG signals are pre-segmented and rectified; then the sinusoidal frequency, amplitude, and phase of the rectified segmented signals are extracted. These estimated sinusoidal parameters from each recorded channel are weighted by their individual signal to noise ratios before being averaged to achieve the optimal powerline frequency, amplitude, and phase. Based on these optimal sinusoidal parameters, the individual sinusoidal waveform is reconstructed and then is subtracted from the corresponding ECG segment, in order to obtain the clean ECG signals. This method of filtering the powerline interference through removal from recorded signals enables accurate measurement without any ringing effect that could lead to signal distortion issues.

Abstract: The technology disclosed in this invention belongs to both the field of Nuclear Quadrupole Resonance (NQR) and nuclear geomagnetic resonance application. Technically, a nuclear quadrupole resonance detection system and its antenna are provided. The antenna includes two coils to make a gradient antenna wherein they simultaneously receive both the signal from the target region and the external radio frequency interference. Structurally, the first coil is positioned as a regular circular coil, while the second coil is annular and evenly distributed around the first coil peripherally. These coils are on the same plane with equal areas but have opposite winding directions. The systems specific to the disclosed antenna are also included. The configuration of the invented antenna can effectively increase the capability of suppressing environmental electromagnetic radio frequency interference, thereby enhancing the detection of the NQR or geomagnetic resonance signals.