Hydro-acoustic Signal Automatic Detection And Processing Research And Implementation Based On FPGA

Nowadays, communication technology develops rapidly, people callcommunication mainly refers to the space wired and wireless communication, thecommunication technology has developed more mature, and underwatercommunication is still in the research and development. In recent years, due to theneed of military and Marine development, people begin to pay more and moreattention to the research and development of communication system in sea. Becausethe electromagnetic wave and light wave propagation is attenuation fast in water, sofar the only effective medium has been found to transmit information underwater issound waves, so the detection, communication, positioning and navigation in theocean, mainly use sound waves. Under this background, the research based onunderwater acoustic communication system has become the hot spot.This article mainly is about the research against the underwater sensor ad hocnetworks acoustic communication, according to the characteristics of the underwateracoustic channel, and the development of the domestic and abroad situation andresearch methods, research the underwater acoustic communication system signals’automatic detection and signal demodulation, designed an automatic detection ofunderwater acoustic communication signal demodulation based on FPGA system, thismethod enhances the anti-interference ability of the system in a certain extent.After introduced the overall structure of underwater acoustic communicationsystem and transmitting the signals transmitted frame format, this article presents themethod of signal detection and signal demodulation, before introducing the signaldemodulation methods, the MFSK signal modulating method is introduced, andprovides a theoretical basis for the determination of signal demodulation method.One of this article’s main job is combined with the research results of currentsignal detection technology to put forward a method of autocorrelation signaldetection. The test method compared with other signal detection methods has the following advantages: low misjudgment rate (or a low false alarm rate), highdetection sensitivity, algorithm is simple, more suitable for hardware implementation,real-time is better. Through FPGA timing simulation verified the feasibility of themethod, FPGA hardware experiment shows that this method can detect the arrival ofthe emergency signal accurately in a relatively short period of time in real-time,timely launch demodulation module started demodulation, greatly reduce the errorrate of the entire communication system, improve the reliability of the communicationsystem.Another main work of this article is combined with modulation module of thesystem MFSK modulation characteristics, study how the receiver demodulatescarrying information contained in the information of the modulated signal informationwhich is sent by sender, because the real-time requirements of underwater acousticcommunication system, the final choice is to use FFT (Fast Fourier Transform)method for demodulation. The FFT demodulation module, including the choice ofdemodulation scheme, the basic principles of FFT algorithm introduction, in situcomputation of FFT demodulation module’s hardware architecture design, the designand FPGA implementation of each module, the demodulation module testing andvalidation process. Demodulation module design uses the base-2extraction methodsto implement according to time. Quartus ii11.0provided by the Altera company assoftware platform, and VHDL is used to describe the way of12bits512point FFTdemodulation, and with cyclone iii series Ep3c10e144c8n as hardware platform,carries on the understanding of the module of the simulation, integration, verificationetc. The final experiment results show that the calculation results of FFTdemodulation module has reached the expected requirements of the project,demodulation speed a lot of times higher than that of DFT (Discrete FourierTransform), can meet the requirements of real-time signal processing in underwateracoustic communication system.