ELF Chirp Communication based on Modulated Heating Low Ionosphere

Abstract

ELF can be generated by HF heating the low ionosphere for submarine communication. QPSK has been used on ELF carried generated via modulated ionosphere heating to transmit digital data. However, ELF band is disturbed frequently by the power frequency harmonic interference, and QPSK modulation can’t effectively suppress interference. In this paper, the Chirp-BOK(Binary Orthogonal keying) modulation method for ELF communication based on ionosphere heating is proposed. The up-chirp and the down-chirp modulation waveforms are designed to transmit the symbols “0” and “1” respectively. Simulation results show that the variation of electron temperature and conductivity in the ionosphere is basically consistent with the frequency modulation characteristics of power modulation when the ionosphere is heated by Chirp-BOK power modulation high frequency wave. The performance of Chirp-BOK and QPSK under harmonic interference is compared, and the simulation results show that Chirp-BOK has better anti-interference performance.