| 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.
|
PDF Full Text Request