软件无线电射频前端的研制

发布时间：2018-06-18 04:01

本文选题：软件无线电接收机 + 频率合成器　；参考：《电子科技大学》2014年硕士论文

【摘要】：软件无线电因其硬件平台的通用性和软件的灵活性受到了广泛的关注,它在军民领域都有着广阔的应用前景。宽带中频数字化结构因其具有的技术成熟、实现相对简单的优势成为了国内软件无线电接收机采用的主要结构。这种结构的接收机性能的优劣直接受到其射频前端的影响。因此,对宽带中频软件无线电接收前端进行研究是非常必要的。本文研究了一种两级变频的超外差式宽带中频软件无线电接收机的射频前端。它的工作频率覆盖30-1350MHz的范围,输出的70MHz中频信号带宽达20MHz。本文分三章对这种结构的架构及整体方案、用作本振的频率合成器和预选组件进行了研究。变频通道的设计主要关注增益、噪声系数、线性度、带内杂散水平等指标。本文通过合理分配各级增益的方式来平衡噪声系数和线性度之间的矛盾;通过选择合适的本振频率来优化中频带内的杂散水平。为了提高抑制度、减轻预选组件的设计难度,变频通道的第一级混频采用上变频方式,第二级混频采用下变频方式。而且将一二本振的频率分别分配在1930-3250MHz和1825-1835MHz,这样一二本振的低阶交调产物不会落入中频带内,从而实现了低幅度的杂散输出。频率合成器设计方面,一本振采用单锁相环、大步进设计,达到快速扫频的目的;二本振采用DDS驱动PLL的结构,实现低于1Hz的分辨率。预选组件由七段滤波器和集成GaAS FET选频开关实现。本文最后还给出了测试数据。测试数据表明,除三阶截点和本振杂散略低于要求外,其他指标均满足设计要求。
[Abstract]:Software Radio (SDR) has attracted wide attention because of its versatility of hardware platform and flexibility of software. It has a broad application prospect in the field of military and civil affairs. Wideband if digital structure has become the main structure of domestic software radio receiver because of its mature technology and relatively simple advantage. The performance of the receiver with this structure is directly affected by its RF front end. Therefore, it is necessary to study the front end of broadband if software radio receiver. In this paper, the RF front end of a two-stage variable frequency ultra heterodyne wideband if software radio receiver is studied. Its operating frequency covers a range of 30-1350MHz, and the output if signal bandwidth reaches 20MHz. In this paper, the structure and overall scheme of this structure are studied in three chapters, which are used as the frequency synthesizer and preselector of the local oscillator. The design of frequency conversion channel mainly focuses on gain, noise coefficient, linearity, in-band stray level and so on. In this paper, the contradiction between the noise coefficient and the linearity is balanced by the rational allocation of the gain at all levels, and the stray level in the frequency band is optimized by selecting the appropriate local frequency. In order to improve the suppression degree and reduce the difficulty of design of pre-selected components, the up-conversion mode is used in the first stage of the frequency conversion channel, and the down-conversion mode is used in the second stage. Moreover, the frequencies of one or two local oscillations are distributed at 1930-3250MHz and 1825-1835MHz, respectively, so that the low-order cross-modulation products of one or two local oscillators will not fall into the middle frequency band, thus realizing the low-amplitude spurious output. In the design of frequency synthesizer, a single phase-locked loop is used in the first oscillator to achieve the purpose of fast frequency sweep, and a DDS driven PLL structure is used for the second oscillator to achieve a resolution of less than 1 Hz. The preselect module is implemented by seven-segment filter and integrated GaAS FET switch. Finally, the test data are given. The test data show that, except for the third order cut point and the local oscillator stray slightly lower than the requirement, the other indexes all meet the design requirements.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN851

【共引文献】