低杂散宽覆盖阵列直接数字频率合成方法研究

项目名称： 低杂散宽覆盖阵列直接数字频率合成方法研究

项目编号： No.60801024

项目类型： 青年科学基金项目

立项/批准年度： 2009

项目学科： 无线电电子学、电信技术

项目作者： 杨远望

作者单位： 电子科技大学

项目金额： 20万元

中文摘要： 本研究在对以直接数字频率合成器（DDS）为核心的微波毫米波频率合成器方案进行调研、论证和设计后，在分析DDS的杂散性能对微波毫米波频率合成器性能影响的基础上，主要研究了：（1）研究无相位截断杂散DDS结构分析与实现，针对传统DDS结构引入相位截断杂散的缺陷提出了一种无相位截断杂散的DDS结构。（2）探讨了使用并联DDS结构对非相关噪声和杂散进行抑制的效果。在理论分析的基础上，对并联DDS结构对不同种类噪声杂散的抑制效果进行了仿真和验证。（3）针对DDS的频率相对覆盖宽但输出频率较低的特点，研究了多重调节的频率合成器结构，提出使用DDS代替可变分频比分频器，以实现多重级联DDS结构。从而扩展DDS输出频率覆盖范围，灵活避开DDS的相位截断杂散和非线性杂散。（4）将并联DDS与多重级联DDS相结合，提出阵列DDS的概念，对阵列DDS杂散抑制性能进行了分析研究，对阵列DDS性能进行仿真验证，搭建阵列DDS的试验硬件平台，实现了基于阵列DDS结构的低杂散宽覆盖捷变频直接数字频率合成器。

中文关键词： 无相位截断杂散结构;直接数字频率合成;阵列;宽覆盖

英文摘要： In this study the advantages and disadvantages of microwave and milli-meter wave frequency synthesizer based on the Direct Digital Synthesizer(DDS) are investigated and discussed. Based on the analysis of the spur supression performance of DDS and it's influence on the performance of microwave and milli-meter wave synthesizer, the study mainly concentrates on: (1)A novel spur-free truncation method for compressing the sine lookup table in a DDS structure is proposed. By introducing a comparator and an adder into the traditional DDS architecture, the sine lookup table can be compressed without significant hardware change in the design. Simulation results using MATLAB and implementation results on FPGA evaluation platform show that the novel structure can eliminate the truncation spurs without increasing the size of the lookup table. (2)A novel DDSs array structure by combining the output of multiple dithering DDS channels is proposed. The methods to suppress the truncation spurs and uncorrelated noise by using phase dithering and parallel DDSs are discussed. Methods for eliminating the truncation spur by combining the output of multiple dithering DDS channels are analyzed to obtain spur-free outputs with low phase noise. Simulation results using MATLAB show that the novel structure can eliminate the truncation spurs without increasing the phase noise. (3)An improved multiple-tunable frequency synthesizer structure to achieve both high frequency resolution and fast switching speed without degradation of spurious signals (spurs) level performance is proposed. Experimental results from the implemented synthesizer show that remarkable performance improvements have been achieved. By replacing the varied frequency divider with another DDS, the multiple-tunable cascaded DDSs structure is proposed to avoid the truncation and non-linear spur of DDS. (4)By combining the cascaded and pararalled DDSs together, the concept of DDSs array is proposed. The results by simulation and hardware testbed show that the structure of DDSs array can obtain signal with excellent performance on spur supression, wide frequency coverage and agile frequency switching speed simutaneously.

英文关键词： truncation spur free; DDS; Array ;wide frequency converage