2FSK Communication System Demodulation Algorithm for Novel Acoustically Excited SLF Antennas

Abstract

There exist some problems for acoustically excited super low frequency(SLF) antennas, such as low transmission power and low received signal-to-noise ratio. In addition, it is difficult to design a narrow-band filter in traditional binary frequency-shift keying(2FSK) non-coherent demodulation. Therefore, a 2FSK weak signal demodulation method based on a Duffing chaotic oscillator was proposed. Because the Duffing oscillator itself was sensitive to the phase, a phase synchronization method of “coarse synchronization + fine synchronization” was designed. The coarse synchronization was accomplished through the short-time Fourier transform, while the fine synchronization was achieved through the Duffing chaotic oscillator. Then, the properties of the chaotic oscillator, such as being sensitive to the same-frequency periodic signal and being immune to noise signals, were utilized, and the signal passed through two Duffing oscillators in parallel, with the built-in signal frequency of the two being consistent with the two carrier frequencies. At a certain moment when one system must be in the large-scale periodic state and the other in the chaotic state, the two systems could be discriminated to realize signal demodulation. The simulation results show that the proposed Duffing oscillator demodulation algorithm outperforms the non-coherent and coherent demodulation algorithms by 5 dB and 4 dB in bit error rate, respectively.

Keywords

• cross-domain communication
• duffing oscillator
• acoustically excited super low frequency antenna
• binary frequency-shift keying
• signal demodulation algorithm