皮卫星测控应答机锁相环嵌套结构的研究

【作者】 郑伟；

【导师】 金仲和；

【作者基本信息】 浙江大学 ， 微电子学与固体电子学， 2005， 硕士

【摘要】 皮卫星是现代航天技术中的重要研究领域。这种卫星重量轻、研制周期短、机动性强、造价与发射成本低，往往采用一箭多星和子母卫星的发射方式，在卫星轨道上形成卫星群以编队飞行的形式覆盖一定的范围，实现卫星之间的资源与信息共享，完成立体成像、分布式空间测量等较复杂的任务，或以更低的成本完成卫星搭载试验等空间科学实验。皮卫星这些优势决定了其在军事、科学研究、商业应用上均将发挥重要作用。 本课题组对MEMS皮卫星项目的研究已经有四年多了，在本人开始研究之前，卫星已经基本上实现了载波通信功能。本人研究生阶段的工作主要包括电路调试和理论分析两个部分。在电路调试方面，进一步优化测控应答机的性能指标，完成了星上系统和整个皮卫星系统的联试。在理论分析方面，对已有的数字式锁相环模型进行了验证，在此基础上建立了锁相环嵌套环路(皮卫星测控应答机的主要构成部分)的理论模型。然后对嵌套环路模型进行了锁定时间和相位噪声等特性的仿真，并进一步用实验验证了仿真结果。最后根据仿真结果对实际电路进行改进，大大提高了测控应答机的性能。 本论文的主要工作和特色可概括如下： 1．深入分析了单个数字式锁相环电路，利用数值方法对其锁定时间、相位噪声和RMS相位误差等特性进行了仿真，并用实际电路进行验证。仿真结果和试验结果吻合良好。 2．在单个数字式锁相环的基础上，建立了锁相环嵌套环路模型并用数值方法对锁定时间和相位噪声特性进行了仿真。仿真结果和实际电路的测试结果吻合较好。根据对仿真结果的分析，对测控应答机的实际电路进行了改进，从而大大提高了测控应答机的性能。 3．介绍了一种单个锁相环的设计方法，并用数值方法对其进行了一些简化，获得了较精确的设计值。结合前面对嵌套环路的分析方法，就可以完成锁相环嵌套环路的设计。 4．对测控应答机中低噪声放大器(Low Noise Amplifier，LNA)和自动增益控制电路(Auto Gain Controllor，AGC)这两个重要模块进行了分析。在ADS的浙江大学硕士学位论文 辅助下，提出了一种LNA设计方法，能够保证测控应答机整机噪声系数最小 同时，根据AGC电路的测试结果拟合出曲线，给出AGC的表达式，便于更 深刻地理解这个模块。5.对测控应答机系统的各项指标进行了详细的测试，并对皮卫星星上系统进行 了温度循环、振动和粒子辐射等可靠性试验。最后，整个皮卫星系统成功的 完成了功能性无线联试。 通过本论文的工作，成功地改进了用于皮卫星的S波段测控应答机，使其跟踪和捕获接收灵敏度都能达到一92dBm，动态范围55dB以上，接收机的捕捉带宽大于50OKHz，捕捉时间减小到5.4ms，并满足温度循环、振动和粒子辐射等可靠性试验。在无线联试中，皮卫星能够根据地面站的指令作出相应的数据采集功能，并发送回地面站系统，从而准确地恢复出皮卫星获得的图像信息和传感器信息。这些结果表明，本文研制的S波段测控机达到或超过设计的指标，并且基本符合工程化的要求。关键词:皮卫星，测控应答机，锁相环，嵌套环路，锁定时间，相位噪声，可靠性更多还原

【Abstract】 The Pico-satellite is an important research area in modern aerospace technologies. The development period, expense of micro-satellite is usually much lower than conventional satellites. The Pico-satellites can construct satellite cluster, sharing resource and information with each other. They can be used in three-dimensional imaging, distributed aerospace measuring, scientific experimentation at lower cost. The Pico-satellite will play ever more important role in military affairs, science research and commercial application with these advantages.The research on MEMS Pico-satellite in our research group began four years ago. Before my research, the satellite has realized initial communicating function with carrier wave. My major contribution to the satellite during my master period includes two parts. On the one hand, I optimized the TT&C transponder’s performance and achieved the integration of the whole Pico-satellite system. On the other hand, the model of the nested-loop PLL, which is the most important component in the TT&C transponder, is established based on the modern charge-pump PLL. The lock time and phase noise characteristics are simulated, and the results are similar with the test results of real circuit. After analyzing the results of the simulation, the TT&C transponder’s performance has been optimized.Main features of this paper are as follows:1. After analyzing the modern charge-pump PLL thoroughly, I simulate the lock time, phase noise and RMS phase error characteristics by matlab. The results of simulation are consistent with the results tested by actual circuit.2. I establish the model of the nested-loop PLL based on modern charge-pump PLL. The lock time and phase noise characteristics are simulated, and the results are similar with the test results by actual circuit. I improved the actual circuits by the results of the simulation, and improved TT&C transponder’s performance.3. A method to design a single PLL circuit is introduced. I simplified the method and improved its accuracy by numerical calculation method. Then I can design thenested-loop PLL combined with the method to analyze the nested-loop PLL.4. The LNA and AGC are two important modules in the TT&C transponder circuit. I bring forward a method to minimize the noise figure of the whole transponder with the help of ADS. I also obtained the AGC expression by fitting the test curves in order to deepen my understanding of the AGC module.5. All test items about TT&C transponder have met the design spec. The Pico-satellite passed the reliability experiments including temperature circulation experiment, vibration experiment and particle radialization experiment. The whole Pico-satellite system realized all functions in the wireless transmission test. Based on research and experiments, the performance of the S-band TT&Ctransponder of satellite is improved in the following dimensions: has sensitivity up to -92dBm; dynamic range wider than 55dB; capture bandwidth of the receiver wider than 500KHz; capture time reduced to 5.4ms. The Pico-satellite has passed the reliability experiments, too. In the wireless transmission test, the satellite can collect the information from CMOS camera and the sensors according the corresponding commands. After receiving the signal from satellite, the earth station can demodulate it and recover the image and sensor curve. All these results indicate that the S-band TT&C transponder we developed reach the design specification and even outperform it and basically meet engineering requirements.更多还原