| Distributed mobile multi-shipborne OTHR (over-the-horizon radar) system is a powerful mobile detection system that is loaded on a number of mobile platforms. The radar system can not only overcome the weak points of the single shipborne ground wave OTHR system, such as low azimuth resolution and poor ability to match the target type, but also has better performances at detection capability, measurement accuracy, viability and so on. There are many key technologies to be resolved for this new radar system. System synchronization, way of signal demodulation and data transmission technology of this radar system are discussed in this paper. And the design is achieved according to the characteristics of the system.Firstly, several commonly used synchronization techniques are analyzed, and whether these technologies are suitable for the radar system is verified. The GPS-based time synchronization method is used to achieve system synchronization and methods of implementation are analyzed. Secondly, whether the non-coherent demodulation is suitable for the system is discussed. Based on the signal resolution and detection mechanism of HF ground wave OTHR, the differences between the coherent demodulation and the non-coherent demodulation are analyzed, according to the phase noise power spectral density. Through theoretical derivation and simulation, the conclusion is that the non-coherent demodulation can reach performance indicators of the current conventional coherent demodulation for specific applications of HF ground wave OTHR, if the local oscillator with low noise and high stability is used. Finally, microwave is used to transmit data between ships and data transmission protocols, data modulation and error control coding are designed according to the characteristics of data transmission in the radar system. |
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