遥测中调制解调及信噪比估计技术研究

发布时间：2018-05-24 13:03

本文选题：遥测 + 软件无线电　；参考：《西南科技大学》2017年硕士论文

【摘要】：遥测是将测量信息通过无线通信传输给远距离终端的一种技术,该技术被广泛应用于导弹卫星等飞行器的飞行测试任务中。随着遥测技术的高速发展,未来遥测系统的技术特点主要向多调制体制、高速率等方向发展,而目前国内遥测系统整体表现为功能单一、设备兼容性差,不能够适应未来遥测任务的发展。针对以上现状,软件无线电(Software Defined Radio,SDR)技术提供了一种有效的解决方法,其核心思想是利用统一硬件平台,采用软件方式实现各通信功能。本研究基于SDR设计思想,利用全数字化方法设计了一种多调制模式中频数字遥测发射机,以适应目前及未来遥测任务的需求。本文首先对遥测信道的非线性特性和带限特性进行了研究分析,结合信道特性和国际遥测标准IRIG 106,选取了PCM/FM、QPSK及SOQPSK调制体制作为研究对象,并对PCM/FM、QPSK和SOQPSK的调制解调算法进行了分析研究,仿真分析了各调制解调技术的相位特性、误码率和频谱效率。针对传统的PCM/FM相干解调算法载波恢复较难的缺陷,给出了一种不需要恢复载波的解调方法,可降低系统实现复杂度;同时,由于现有SOQPSK调制信号的带外频谱衰减较慢,本文通过优化其频率脉冲函数,给出了一种改进的SOQPSK调制方法,通过仿真结果,证明了改进后的SOQPSK调制信号具有更快的带外衰减特性。此外,本文在加性高斯白噪声信道环境下,对自适应调制中的关键参数—信噪比,进行了估计分析。针对几种现有典型的非数据辅助信噪比估计算法存在估计精度差和估计范围窄的缺点,提出了一种改进的信噪比估计算法。通过仿真说明了改进算法的信噪比估计性能优于原有算法,为多调制遥测系统的自适应调制提供了依据。最后,本研究利用Verilog硬件描述语言编写了各调制算法的FPGA实现代码,完成了Modelsim功能仿真验证与实际测试,测试结果验证了本设计的有效性。
[Abstract]:Telemetry is a technology that transmits measurement information to remote terminals through wireless communication. It is widely used in flight test missions of missile satellites and other aircraft. With the rapid development of telemetry technology, the technical characteristics of the future telemetry system mainly develop in the direction of multi-modulation system and high speed. At present, the whole domestic telemetry system is characterized by a single function and poor equipment compatibility. Unable to adapt to the development of future telemetry missions. In view of the above situation, the software radio Defined radio SDR (Software Radio Defined) technology provides an effective solution. Its core idea is to use the unified hardware platform and software to realize the communication functions. Based on the design idea of SDR, a multi-modulation mode intermediate frequency digital telemetry transmitter is designed by using all-digital method to meet the needs of current and future telemetry tasks. In this paper, the nonlinear characteristics and band limit characteristics of telemetry channel are studied and analyzed. Combining the channel characteristics and the international telemetry standard IRIG 106, PCM / FM QPSK and SOQPSK modulation system are selected as the research objects. The modulation and demodulation algorithms of PCM / FM QPSK and SOQPSK are analyzed, and the phase characteristics, bit error rate and spectrum efficiency of each modulation and demodulation technology are simulated and analyzed. Aiming at the disadvantage of the traditional PCM/FM coherent demodulation algorithm, a demodulation method without carrier recovery is proposed, which can reduce the complexity of the system. At the same time, the out-of-band spectrum attenuation of the existing SOQPSK modulation signal is slow. This paper presents an improved SOQPSK modulation method by optimizing its frequency pulse function. The simulation results show that the modified SOQPSK modulation signal has faster out-of-band attenuation. In addition, the signal to noise ratio (SNR), a key parameter in adaptive modulation, is estimated and analyzed in additive Gao Si white noise channel. A modified SNR estimation algorithm is proposed to overcome the disadvantages of poor estimation accuracy and narrow estimation range in several typical non-data-aided SNR estimation algorithms. The simulation results show that the performance of the improved algorithm is better than that of the original algorithm, which provides a basis for adaptive modulation of multi-modulation telemetry systems. Finally, the FPGA implementation code of each modulation algorithm is compiled by using Verilog hardware description language, and the Modelsim function simulation and actual test are completed. The test results verify the validity of the design.
【学位授予单位】：西南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN911.3

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