L波段宽带高速跳频频率源的研究

【作者】 吴磊；

【导师】 喻梦霞；

【作者基本信息】 电子科技大学 ， 无线电物理， 2010， 硕士

【摘要】 跳频通信是扩频通信的一种,具有抗干扰、抗截获的能力,并且能做到频谱资源共享。所以,跳频通信已经成为现代军事无线通信抗干扰的主要手段,对于在恶劣的电磁环境中保障我军通畅的通信指挥,具有重大的军事意义。跳频通信系统的核心部分是:跳频序列发生器、频率合成器。宽带跳频电台要求设计的跳频频率合成器输出频率转换时间快、跳频带宽宽、输出的杂散和相位噪声低以及体积小、重量轻等特点。对此,在分析总结了频率合成技术及其各种实现方案利弊的基础上,针对实际应用,本文选择了直接数字频率合成方案,着眼于提高DDS的输出频率,增加输出带宽,提高DDS输出的杂散抑制能力,同时又不影响其输出的相位噪声和频率切换时间的指标。直接数字频率合成器具有频率分辨率高、换频速度快等特点。但是DDS同样存在频率上限不够、高功耗以及杂散不好等技术难题。这也是本文需要解决的几大难题。DDS部分选用的是ADI公司的产品AD9910。该方案采用DDS输出端直接接倍频器倍频,以提高输出频率、增加带宽。用此方案设计的频率源最终达到了以下技术指标:输出频率范围为1350MHz～1850MHz,频率间隔为1MHz,换频时间要求小于10μs,跳速为100000Hops/s,相位噪声优于-70dBc/1KHz,完全满足宽带快速跳频电台频段覆盖宽、换频时间短、相位噪声低等要求。更多还原

【Abstract】 Frequency hopping communication is one of the spread spectrum communications, which has the ability of the anti-interference and anti-interception, and the superiority of spectrum efficiency. Therefore, the frequency hopping communication becomes the main method for combating the interference in the modern military wireless communications. It is significant for guarantying the performance of the communication command in the harsh electromagnetic environment. The core parts of the frequency hopping communication systems are frequency hopping sequence generator and the frequency Synthesizer.Wideband frequency hopping radio station requires that the output of the frequency synthesizer has the fast frequency conversion, wide bandwidth, lower spurious, lower phase noise, reduced volume and weight. Based on the discussion of the frequency synthesis techniques and the analysis of the various realization methods, and aiming at the engineering application, this dissertation chooses the direct digital frequency synthesis scheme. The design consideration is to increase the working frequency of the DDS, increase the output bandwidth, and to improve the ability of suppressing the spurious. Meanwhile, the others parameters are not effected.DDS has the characteristics of high frequency resolution and fast frequency conversion. However, the difficulties of DDS are also considerable, such as the limited upper frequency, high power consuming and bad spurious performance. And this dissertation is trying to address the solution of these problems.The proposed scheme adopts the direct connection between the DDS and frequency multiplier. The output frequency and bandwidth could be improved. The following targets are achieved for the proposed scheme in this dissertation. The frequency range is from 1350MHz to 1850MHz. the frequency interval is 1MHz. The frequency conversion time is shorter that 1μs and the hopping rate is 100000Hops/s. the phase noise is below -70dBc/1KHz. In summary, the system satisfies the requirements of the fast frequency hopping radio station on wideband coverage, short conversion time and low phase noise.更多还原