1、分类号 密级 公开 UDC 编号 800212008S13 中国科学院研究生院 硕士学位论文 毫米波固态源自动调谐系统的研究 孙 艳 红 指导教师 姚骑均 研究员 中国科学院紫金山天文台 申请学位级别 硕士 学科专业名称 天体物理 论文提交日期 2008 年 6 月 论文答辩日期 2008 年 6 月 培养单位 中国科学院紫金山天文台 学位授予单位 中国科学院研究生院 答辩委员会主席 陈善怀 研究员 摘要 摘 要 随着射电天文的发展，对射电望远镜接收机的灵敏度和稳定性的要求越来越高。作为外差接收机系统的关键组成部分 - 锁相本振系统，传统手动调谐方式的局限性越来越明显，主要表现在如下几点：手动
2、调谐一般靠操作人员的经验来调整本振的频率、功率和衰减器的衰减量，调节的周期比较长，不利于快速频率切换观测；当整个系统工作在昼夜温差比较大的环境，本振的自由振荡频率和输出功率都会随温度变化发生漂移，同样衰减器的衰减量也会随着环境温度的变化而改变，手动调谐不可能对其做到实时补偿。因此研究观测所需要的自动调谐毫米波锁相固态源系统显得日益重要。自动调谐系统能够实现对整个本振系统的远程控制，能够快速、准确的进行锁相本振调谐。同时通过本振偏压的控制可以实现对温度引起的频率漂移和衰减器衰减量的补偿，通过邻近信道功率-Adjacent Channel Power(ACP)分析能够快速判断锁相环路的质量，进而通
3、过调节锁相环路增益等方式降低本振源的相位噪声。 本文的主要研究工作和结果如下： 1、基于 XL800A 模块的锁相本振自动调谐系统硬件设计和实现。系统设计中，采用了可编码驱动微距丝杆( )替代普通手动丝杆，利用单片机实现对多个丝杆进行选择、驱动及通过码盘解码得到丝杆的位置，同时实现对锁相环路增益和偏压的控制。 TMEncoderDrive Micropositioner2、自动调谐系统软件程序的设计。设计了耿氏振荡器的频率、功率和衰减器的衰减量与丝杆位置的关系校准软件，以及 整个系统自动调谐实现的软件流程。 3、建立在自动调谐系统的基础上进行 W 波段衰减器特性的研究。 W 波段衰减器特性包括
4、频率特性和温度特性，即衰减量随频率和环境温度改变的变化特性。测试结果表明，衰减量随着输入信号的频率和周围环境温度的增加而增加。实验结果还表明，衰减量与丝杆位置存在较大的非线性区域，这也体现了在自动i毫米波固态源自动调谐系统的研究 调谐系统建立前进行衰减量与丝杆位置关系的校准的必要性。 4、采用欠采样的方法对中频监测信号进行 ACP 分析。为实现对锁定信号质量的分析，基于欠采样技术设计了中频监测信号的频谱分析系统。该系统中，锁定监控信号经过放大、滤波和高速 A/D 欠采样，引入缓冲机制实现突发模式下高速中频采样数据到远程控制计算机之间的低速传输。由远程计算机进行数据处理后（ACP 分析），进而判
5、断锁相本振源的相位噪声，为进一步提高信号质量提供依据。同时分析了锁相环路相位噪声的主要来源，提出了降低锁相环路相位噪声的措施。 关键词：毫米波本振系统， 自动调谐， ACP 分析 iiAbstract Investigation on the Automatic Tuning System for Millimeter-wave Solid State Source Yan-Hong Sun (Astrophysics) Advisor: Qi-Jun Yao Abstract With the development of radio astronomy, the sensitivity a
6、nd stability of radio telescope receiver is desired to be as high as possible. The phase-locked local oscillator source system, a key part of the heterodyne receiver, adopts the manual tuning mode. The limitations of the manual tuning mode are shown as follows: It usually depends on the operators ex
7、perience to tune the frequency, power of the local oscillator and the attenuation of the attenuator, since the tuning process may take long time, it is inconvenience when fast frequency switching is required; When the whole system works in the environment where the diurnal temperature varies in a wi
8、de range, the frequency and the output power of the local oscillator and the attenuation of the attenuator will drift with the temperature. For above reasons the investigation on the automatic tuning of the millimeter-wave solid state source system turns out to be increasingly important. The automat
9、ic tuning system can realize the remote control of the local oscillator system and speed up the phase-locked local oscillator tuning. In addition, it can compensate for the drift of the local oscillators frequency and the attenuators attenuation by the local oscillators bias voltage control, identif
10、y the quality of the phase-locked system by the ACP analysis and reduce the phase noise of the local oscillator source by means of tuning the loop gain and so on. Four major parts of this thesis are outlined as follows: 1. The hardware of the phase-locked local oscillator automatic tuning system was
11、 designed and realized based on the XL800A mode. In the system design, the IInvestigation on the Automatic Tuning System for Millimeter-wave Solid State Source TMEncoderDrive Micropositioner was used as a substitute of the normal micropositioner; The MCU (micro control unit) was used to choose and d
12、rive the mocropositioners, read the encoder value that indicates the position of the micropositioner and control the loop gain and bias voltage. 2. The software flowcharts about the automatic tuning system were designed. The calibration flowcharts of the Gunn oscillators frequency and power and the
13、attenuators attenuation to the micropositioners position were designed. And the software flowchart of the automatic tuning system was also designed. 3. The characteristics of W-band attenuator were investigated based on the automatic tuning system. The characteristics of W-band attenuator are about
14、the frequency and temperature, which include the correlation of signal frequency and ambient temperature to attenuation respectively. The measured results show that the attenuation is proportional to the input signal frequency and the ambient temperature. From the experiment, we can also get that th
15、e linear range of the attenuation is limited and the calibration table of the attenuation is needed. 4. The adjacent channel power (ACP) of the IF signal was analyzed by means of the under-sampling. To know the quality of the locked signal, we designed the spectrum analysis system of the IF signal b
16、asing on the sub-sampling technology. In this system, the locked signal was amplified, filtered and under-samplinged; The buffer mechanism was introduced in realizing the transmission from the high sampling transmission in the burst mode to the low transmission of the remote control computer. After
17、the datas are processed by the remote computer, the phase noise of the phase-locked local oscillator source can be calculated to provide us the direction of tuning for improving the signals quality. The main sources of the phase noise were analyzed and some corresponding measures to reduce the phase
18、 noise were also discussed. Keywords: millimeter-wave local oscillator system, automatic tuning, ACP analysisII目录 目 录 第一章 绪论1 1.1 引言 1 1.2 与SMA中的自动调谐系统的比较 3 1.3 本文研究的意义 3 1.4 论文工作内容概述 4 第二章 毫米波锁相固态源系统6 2.1 毫米波信号源 6 2.2 锁相本振系统 8 2.2.1 毫米波锁相本振系统结构及基本原理 .8 2.2.2 锁相环路的基本原理 .10 2.2.3 锁相环路各部件的工作原理 .12 2.2
19、.3.1 鉴相器 .12 2.2.3.2 环路滤波器 .14 2.2.3.3 压控振荡器 .16 2.2.4 锁相环路的主要性能分析 .17 2.2.4.1 锁相环的线性相位分析 .17 2.2.4.2 锁相环的捕获性能分析 .19 2.2.4.3 锁相环的跟踪特性分析 .20 2.2.4.4 锁相环的噪声性能分析 .20 2.3 小结 22 第三章 自动调谐基本原理及设计.23 3.1 自动调谐基本原理 23 i毫米波固态源自动调系统的研究 3.2 系统硬件电路的设计与实现 26 3.2.1 单片机模块 .27 3.2.2 串口通信模块 .29 3.2.3 驱动和解码模块 .37 3.2.4
20、 增益控制和偏压控制模块 .43 3.3 系统程序软件设计与实现 45 3.3.1 自动调谐系统的程序流程 .46 3.3.2 耿氏振荡器的频率、最大功率与丝杆位置关系的校准 .50 3.3.2.1 测量自由振荡时耿氏振荡器的频率与丝杆的位置关系 .50 3.3.2.2 测量自由振荡时耿氏振荡器的功率与丝杆的位置关系 .57 3.3.2.3 环路锁相时修正耿氏振荡器的频率与丝杆的位置关系 .60 3.3.4 衰减器的衰减量与丝杆位置关系的校准 .61 3.4 小结 65 第四章 衰减器特性的分析.66 4.1 毫米波衰减器原理及自动控制实现 66 4.2 衰减器的频率特性 70 4.3 衰减器的温度特性 73 4.4 小结 75 第五章 邻近信道功率分析.76 5.1 锁相环路的相位噪声分析 76 5.2 邻近信道功率分析的方法 78 5.2.1 邻近信道功率分析的简介 .78 5.2.2 欠采样 .80 5.2.3 AD 芯片的选择 82 5.2.4 数据处理 .83 5.3 小结 86 ii
