【作者】 张虹；

【导师】 沈保锁； 侯永宏；

【作者基本信息】 天津大学 ， 通信与信息系统， 2007， 硕士

【摘要】 近年来,卫星通信以其它通信方式所无法比拟的优势得到迅猛发展。本文重点研究卫星通信中的载波同步技术。同时进行了大量仿真,由于安捷伦公司推出的ADS有着强大的功能和优势,被普遍接受,因此全文采用ADS进行仿真。在论文的相应部分给出了利用ADS进行仿真的结果,这对将来的实际应用提供了一定的参考价值。在卫星数据传输系统中,载波同步就是为了能够更好的进行解调。所以,本文首先对卫星通信中的调制技术进行了深入的介绍和对比研究,对其进行仿真并给出仿真结果作为载波同步的铺垫。在载波同步的研究中,分为两部分:载波频偏和载波相偏进行研究。在载波频偏估计和校正中,主要研究了三种频偏估计方法:频偏粗估计、频偏细估计和开环快速频偏估计。开环快速频偏估计是对于现有载波频偏估计算法结合卫星通信数字接收项目进行了改进。通过ADS进行仿真验证,性能明显高于频偏细估计和频偏粗估计法。它不仅估频速度快而且对于低噪声比的情况下仍然有较稳定的性能,适用于卫星通信,特别是适合于卫星通信的突发信道,满足了对于突发传输的快速、低信噪比的要求。在载波相偏的估计和校正中,研究了适合卫星通信的方法:最大似然法,锁相环法,针对实际卫星通信项目的改进了适合突发OQPSK相偏快速估计方法。锁相环的方法适合卫星通信数字接收项目的连续信道,而突发OQPSK的相偏快速估计方法,是根据实际项目需要,对现有开环算法的改进。它针对突发信道的传送特性,实现了快速捕获相偏的能力,解决了突发传输时相偏估计在低信噪比时不准确的难题,适合接收机结构的全数字实现。通过对上面几种方法进行ADS仿真,验证了突发OQPSK相偏快速估计方法的快速有效性,它对移动通信、卫星通信等需要突发传送模式的场合具有普遍意义。为了对载波同步的性能进行评估选取著名的克拉美罗界(CRB)作为理论参考值进行比较,得到了满意的结果,再次证实了突发OQPSK相偏快速估计法的优越性。更多还原

【Abstract】 Nowadays, satellite communication develops rapidly since its dominance while compared with other means of communication modes. This paper emphasizes carrier recovery techniques in satellite communication. Lots of simulations have been made with ADS (Advanced Design System) which produced by AgilentTechnologies. It has powerful function, so it is universal acceptanted and in general use. This paper shows the simulation with ADS. It provides practical application of a certain reference value. In the satellite data transmission systems, carrier synchronization is to be able to better carry out demodulation. Therefore, first introduce satellite communications of modulation and demodulation techniques as paving the way. Carrier Synchronization in the study, divided into two parts: carrier frequency offset and phase offset research. Carrier Frequency Offset Estimation and correction gives three different ways:Offset rough estimate, Offset subtle estimate, and the open-loop rapid estimation. The last one is the improvements of existing carrier frequency offset estimation and its ADS simulation test performance significantly higher than the other two. It estimated frequency speed and low-noise ratio at the same time have a more stable performance which met for the rapid transmission.Carrier phase offset in partial estimates and correction, several research methods are given: the maximum likelihood method, PLL, and the very applicable to the burst OQPSK phase offset rapid estimation method. Particularly the last algorithm, based on the actual project requirements, of the existing open-loop algorithm improvement. It meets sudden channel transmission characteristics, theoretical analysis, rapid capture capability. Among the three methods, burst OQPSK phase offset rapid estimation has universal significance for mobile communications, Satellite communications needs of burst transmission mode. Finally, focuses on the famous Cramer-Rao bound, burst OQPSK phase offset rapid estimation method simulated by ADS,results with the theoretical value compared is satisfied which approves its superiority again.更多还原