【作者】 张朝柱；

【导师】 杨莘元；

【作者基本信息】 哈尔滨工程大学 ， 通信与信息系统， 2002， 硕士

【摘要】 本课题出自我校目前承担的国家973科研项目。以水下作战平台对母舰的短波通信为背景，对海上近距短波通信系统的总体方案进行初步论证。其中包括电波传播形式的论证、工作频段的选择、通信体制的选择、接收机总体指标以及接收机采样部分技术论证。具体内容如下： 1．综合阐述了国际无线电咨询委员会报告中有关短波地波、天波场强的估算方法，并对我国南海台湾岛周边海域上200公里的作用距离下地波、天波场强进行了具体计算。得出天波传播的最高可用频率、可能的最强天波场强，并与相应的地波场强进行了比较，阐明了海上200公里距离上的短波通信中电波主要是以地波的形式传播的，天波对地波通信的多径干扰问题可以忽略的结论。这为采用地波通信形式提供了依据。 2．对海上地波通信系统可利用的工作频段进行了系统研究。在计算出不同频率下地波场强的同时，重点介绍大气无线电噪声场强的计算方法，并给出相关海域上夏季不同时段内大气噪声场强的有效值。综合地波场强与大气噪声场强跟工作频率的关系，得出了工作海域上地波通信系统输入信噪比与工作频率的关系曲线，为工作频段的合理选择提供了基础。同时也给出通信系统输入信噪比的大致范围。 3．综述了扩频通信系统的基本原理及其抗干扰性能，全面阐述了选取扩频通信体制的主要根据。同时对扩频调制方式、射频信号调制方式以及波形参量的选择进行了重点的论述，并对扩频通信系统的相关指标进行了计算。 4．针对接收机的各项指标进行了分析计算，给出接收机射频子系统、信号处理子系统的原理框图。并对无线电接收系统向软件化方向发展中采样技术的运用作了综合的讨论。分别对低通采样、正交带通采样和直接带通采样技术中有关A／D在系统中的位置、采样率的确定、信息获取和滤波参数选取等问题进行系统论述，并讨论了各自的技术实现问题。更多还原

【Abstract】 This subject is one part of the researching project of national "973" which we joined. It’s briefly demonstrated that the overall plan of the close range shortwave marine communication system, which including format of radio propagation, operation frequency, communication architecture, main parameters and the sampling part of receiver. The detail is as follows:First, it’s demonstrated that the calculation of HF groundwave and skywave field strength according to the report of CCIR. And the numerical evaluation of groundwave and skywave field intensities are computed in the ocean region 200 kilometers around Taiwan. The MUF and the possible maximum skywave field strength are calculated and are compared with the corresponding groundwave. And the conclusion is that the main propagation mode 200 kilometers on the sea is groundwave and the disturbance of skywave could be omitted.Second, the possible operation frequency bands are studied for groundwave marine communication system. The method of calculation atmosphere noise is discussed and the detailed root mean square numeric values of different time of summer are obtained. The curve which describes the relationship between input SNR and frequency of operating is made which could be used in choosing the operation frequency band.Third, the rational and anti-jam properties of spread spectrum communication system are summed up. And the spreading modulation, radiation signal modulation and choosing of waveform parameters are also discussed, which is the base of the receiver designing.The last, the block diagram of receiver radio subsystem,signal processing subsystem are got after the calculation of the whole parameters. The sampling technology is also being explored which including lowpass sampling, quadrature sampling and direct passband sampling and the setting of A/D, sampling rate, data acquisition and selecting filtering parameters. The implementation of each technique is also being discussed.更多还原