上海交通大学
硕士学位论文
通信信号调制识别与解调技术研究
姓名：莫乾坤
申请学位级别：硕士
专业：电子与通信工程
指导教师：何晨；丁伟强
20080901
通信信号调制识别与解调技术研究
摘要
通信信号的调制方式识别技术是将接收或截获到的通信信号经过特定的分析处理，从而自动的识别出信
号调制类型的新技术。本课题主要研究调制识别分类算法，并结合软件无线电的数字化解调技术，研制出具有通信信号调制方式的自动识别和解调功能的调制识别和解调原理样机。
本文首先叙述了信号调制识别技术研究的意义、国内外技术状态和发展趋势，然后在调制识别技术研究方案、软硬件设计、原理样机实现、指标测试各方面做了详细的阐述。设计采用软件无线电接收机的结构，输入中频信号频率为70MHz，信号经放大、模/数变换后送高速FPGA和DSP信号处理板数据处理。在识别算法上，采用基于特征提取的统计模式识别方法，通过提取信号的特征参数对信号分类。在识别出信号的调制体制后，可进一步进行解调处理。解调使用软件无线电数字化实现，灵活性高，通过修改软件配置，能适应各种调制信号形式。为了取得较好的解调灵敏度、动态范围和误码性能，采用相干解调方式，在接收端恢复与发射端同频同相的载波信号。在MATLAB仿真的基础上，将识别和解调算法在FPGA和DSP中进行了硬件实现。其中FPGA主要完成信号的数
字下变频率，数字滤波，载波跟踪和信号的解调功能，DSP主要完成信号的分类识别算法。最后，在输入信号存在不同的多谱勒频率，输入电平，信噪比，调制方式下对调制识别原理样机进行了测试，测试结果指标基本达到了工程应用的要求。
关键词：调制识别，软件无线电，数字化解调，FPGA，DSP
THE RESEARCH OF COMMUNICATION SIGNAL MODULATION RECOGNITION AND DEMODUL
modulateATION
ABSTRACT
The communication signals modulation recognition technology is a technology to recognize the modulate pattern by processing and analyzing the received or captured signals based on their characteristics. In this project, the algorithm of communication signal modulation recognition is discussed, a modulation recognition and demodulation receiver is designed and implemented, where auto-recognition function is realized, base on the software radio and digital demodulate technology.
In this paper, the importance of the research on modulation recognition, and the status of technology in this area are discussed. Then the scheme of the project, software design and hardware implementation together with regression testing are elaborated. The Software Define Radio (SDR) structure is adopted in the design of the modulate pattern recognition and demodulation receiver. The receiver uses communication signal with intermediate frequency of 70MHz as the input, then amplifies it, pass it to an Analog to Digital converter, after that, processed it in FPGA and DSP board. The algorithm of communication signal modulate pattern recognition is done with statistic
methods on signal characteristic extraction and sorting. To make the receiver available to all kinds of
communication signals, SDR structure is adopted, software is designed as configurable to make the receiver flexible and tunable. Meanwhile, to achieve better signal locked threshold, dynamic range and BER performance, correlation demodulation is used in the receiver. Based on MATLAB simulation results, the algorithm is written into DSP and FPGA devices thus the modulate pattern recognition and demodulation receiver is completed. The digital down-converter, digital filters, carrier tracker and demodulator are done in FPGA board. In DSP board, the algorithm of communication signal modulate pattern recognition is implemented. In the end, a regression test is carried out with the receiver placed under different Doppler frequencies, signal input levels, SNR and modulate patterns, testing result shows that the receiver can meet the demands of engineering.
KEY WORDS: Modulation recognition, Software Define Radio (SDR), Digital demodulate, FPGA, DSP
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