短波跳频电台频率合成器的设计与实现

发布时间：2018-06-29 04:39

本文选题：短波通信 + 跳频　；参考：《西安电子科技大学》2015年硕士论文

【摘要】：本论文直接来自工程某型短波数字化电台的工程研制过程,具有重要的现实意义和广阔的应用前景。该电台采用数字信号处理技术(DSP)完成了对中频信号的数字化、基带信号的调制解调、数字话、数据等业务功能以及通信的自动化。应用了第三代短波自适应跳频通信体制(3G-ALE)使本电台可以在短波波段内实现分波段跳频,从而实现了短波电台的抗干扰能力,并可对数字话和数据进行加密,有力地保证了传输信息的安全性。本论文设计的频率合成器单元是短波跳频电台实现抗干扰的关键部件,该单元一本振信号的跳变最终反映在电台载波频率的跳变上,所以该单元的指标性能对短波电台的性能同样有着不可忽视的影响。本论文首先从公司已应用频率合成器方案存在的问题入手,对已应用频率合成器进行了结果测量并给出测量频谱图、相噪图及具体的杂散数据值,并分析了频谱问题的主要来源。在不改变原方案的基础上,经试验给出杂散和相噪的改进措施,得出改进前后的杂散数据值对比情况。由此提出本课题中的DDS+PLL混合的频率合成器方案,对频率合成器单元做出进一步优化,目的在于实现一款高稳定度、低成本、低相噪、低杂散、高分辨率并满足频率切换时间要求的频率合成器。相对已应用频率合成器,在电路原理设计上,考虑了频率合成器单元一、二本振的独立性,以减少互相之间的串扰现象；在器件选型上,提高了对影响频率合成器频谱性能的器件要求,如VCO、TCXO、DDS及二本振锁相环芯片；在PCB排板上,采用四层排板,在中间层模块化独立铺地,并将易受干扰的电路进一步增加屏蔽措施；鉴相频率和环路带宽的选择上,本着不影响电台要求的频率切换时间情况下,尽量考虑缩小环路带宽并提高鉴相频率的设计；从低成本性考虑,取掉了已应用频率合成器一本振充电泵所需的升压电路,以及用一片锁相环芯片代替了原二本振锁相环芯片及独立的充电泵电路。历经器件选型、电路设计、PCB排板、仿真调试实验、结果测量及分析等过程后,设计和实现了一款满足某型短波数字化电台提出的指标要求的最优频率合成器单元。
[Abstract]:This paper is directly from the engineering development process of a short wave digital radio station in engineering , and has important practical significance and wide application prospect . The radio station adopts digital signal processing technology ( DSP ) to realize the frequency synthesizer with high stability , low cost , low phase noise , low spurious and high resolution and meets the requirement of frequency switching time .
In the device selection , the device requirements for frequency synthesizer spectrum performance are improved , such as VCO , TCXO , DDS and LO phase locked loop chip .
on the PCB board , a four - layer row plate is adopted , the middle layer is modularized and independently paved , and the interference - prone circuit is further increased shielding measures ;
In the selection of phase discrimination frequency and loop bandwidth , the design of reducing the loop bandwidth and improving the phase discrimination frequency should be considered as much as possible without affecting the frequency switching time required by the radio station ;
Considering the low cost , the step - up circuit required for a vibrating charge pump with a frequency synthesizer is taken out , and a single phase - locked loop chip is used instead of the original two - local oscillator phase - locked loop chip and the independent charge pump circuit . After the process of device selection , circuit design , PCB layout , simulation debugging experiment , result measurement and analysis , an optimal frequency synthesizer unit is designed and realized to meet the requirements of a certain type of short - wave digital broadcasting station .
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN74

【相似文献】