Signal acquisition and amplitude extraction from high-frequency coupling sinusoidal signal

In electro-magnetic coupling sensing system, the amplitude of the coupling signal should be obtained by AC signal sampling. We use the direct sampling and the signal processing calculation method to determine the signal amplitude. The coupling sensitivity of electro-magnetic coupling sinusoidal signal is related to the frequency of signal. When the frequency of signal increases, the sampling rate should be enhanced, and thus the complexity of system becomes high. In this paper, we propose an amplitude and phase extraction method from the high-frequency coupling sinusoidal signal. Its specific feature is that when signal frequency increases, the sampling period remains constant; this makes the system easier to implement. Then the least square fitting method (LSM) is applied to compute the amplitude and phase of the signal linearly. The method is evaluated by the simulations with different level noises and frequency offsets on the on the signal amplitude parameters. The results show that if there are enough samples, this method can recover the signal with under noises and achieve high signal accuracy and high execution speed. When there is a deviation in frequency, the algorithm uses the golden section algorithm to find the best frequency and the most accurate sinusoidal signal amplitude, so that the limit of frequency range is greatly reduced.