The Software And Hardware Design Of Spread Spectrum Underwater Acoustic Communication Machine

Long-range underwater acoustic communication and low signal-to-noise ratio underwater acoustic communication mainly rely on spread spectrum underwater acoustic communication technology.Spread spectrum technology has many advantages: strong anti-interference ability,high security,high bandwidth utilization,and good anti fading ability,so it is widely used in military and civilian wireless communications.This article will combine spread spectrum communication technology to design a set of underwater acoustic communication machine that can be applied to UUV platform.In this paper,the underwater acoustic spread spectrum communication technology is studied first.The good autocorrelation property of the spread spectrum code makes the DS system have a certain anti-multipath ability,but the anti-Doppler ability of the DS system is poor.Aiming at the problem of carrier phase jump caused by Doppler effect,the differential spread spectrum system is studied,and a symbol differential correlator based on quadrature demodulation is proposed on the basis of differential correlation detector.In the estimation of Doppler factor,the fuzzy function estimation method and the Doppler estimation method based on LFM signal are introduced,and the two methods are compared by simulation.Secondly,based on the application scenarios of the communication machine,the overall design scheme of the underwater acoustic spread spectrum communication machine was proposed,with a focus on the detailed design of A/D,D/A circuits,signal conditioning circuits,pressure acquisition and synchronization modules,and power supply modules.According to the actual requirements of underwater acoustic communication machines,ZYNQ7020 is selected as the main control board card of the core control unit,and the eight core TMS320C6678 chip is selected as the core processor.Then,the system software was designed on the ZYNQ7020 and DSP C6678 platforms.The FPGA end mainly realizes the collection and transmission of signals,the ARM end implements the packaging and transmission of collected data,as well as the reception and transmission of upper computer instructions.The DSP end mainly realizes functions such as synchronous signal detection,Doppler estimation,and information code decoding.Finally,the underwater acoustic spread spectrum communication machine was tested and validated: in a laboratory environment,the parameter indicators of the signal conditioning circuit,the collection and transmission functions of A/D and D/A,the network transmission of the ZYNQ platform,the command transmission and reception functions,and the DSP decoding function were tested.Finally,a lake experiment was conducted to demonstrate that the designed underwater acoustic spread spectrum communication machine has stable and reliable modules,and can achieve low bit error rate communication over long distances.