Study Of Power Modulation Technique In Underwater Acoustic Transmitter

With the development of ocean exploitation and demand of national defense, sonarsystem becomes more and more important. Underwater acoustic transmitter as a veryimportant component of sonar system, its quality performance has a significant impact to thewhole sonar system. In order to obtain better performance, the transmitter structure iscontinuously improved and at the same time the research of underwater communicationsystem has attracted more and more attention. The modulation signal has been applied to theunderwater acoustic transmitter. Advantages of the pulse width modulation (PWM) techniqueinclude the earliest development, most mature technology, most extensive range ofapplications, strong capability of anti-jamming, simplicity of circuit structure, a higher overallefficiency and so on. Pulse step modulation (PSM) technique is mainly used in high-powerradio transmitter currently, which has the advantages of a frequency bandwidth, highefficiency, high output power and so on. Based on the above characteristics which are thedemands of underwater acoustic transmitter, PSM technique is worthy of being applied to theunderwater acoustic transmitter.This paper introduces the basic principles of the PWM and PSM. Based on the PWMmodulation transmitter, we discover the relationship between degree of distortion andsampling times by theoretical calculation of sampling rate. The quantization error of PSMtechnique is theoretically analyzed also. Using small signals error compensation, the signaldistortion is effectively reduced without increasing the complexity of the circuit. Based on thetheories, spectral analyses of PWM and PSM are examined respectively, which providetheoretical guidance for the late signal demodulation. This paper discusses the implementationof underwater acoustic transmitter on the basis of PWM and PSM techniques. We alsocomplete the design and implementation of underwater acoustic transmitter circuit.According to the experimental data as well as questions found in the process ofexperimental design and debugging, we conclude that PWM and PSM are suitable forapplications in underwater acoustic transmitter.