Research on positive and negative slope LFM signal joint coding communication technology based on fractional Fourier transform

In order to improve communication rate and frequency band efficiency of the underwater acoustic (UWA) communication system, a new method using positive and negative slope LFM signal joint coding based on fractional Fourier transform (FRFT) was presented in this paper. And this scheme had strong anti-noise performance and good robustness. Under the premise of not occupying additional system frequency band resource, the slope of LFM signal was used as coding information, and the fractional Fourier transform was used as demodulation method at receiving end. The Rake receiver was proposed to suppress the inter-symbol interference (ISI) arising from multipath effect of the UWA channel. Through the simulation and water pool experiment, the communication rate can reach up to 1600bit/s.