超短波通信具有稳定性高、抗毁性强以及适用功率较小的发射机等特点，得以广泛应用于军事通信和民营广播等多个无线通信领域。随着现代无线通信技术的发展，频带资源愈加紧缺，针对通信带宽和功率都受到一定限制的超短波传输系统，一方面考虑选用优良的调制方式，并联合采用高性能的信道编码技术，另一方面需要考虑对抗无线信道中的多径干扰，由此实现高效且高可靠性的信息传输。

       基于上述背景，本文以具有高功效和高谱效的连续相位调制(Continue Phase Modulation, CPM)技术为核心进行波形设计，并实现了高阶CPM调制的FPGA设计，为基于CPM的超短波传输波形的应用提供了支撑。

       首先，本文详细介绍了CPM的关键技术，包括CPM信号的定义及相位状态，利用CPM信号的Rimoldi分解模型推导了CPM信号的最大似然序列检测，并对影响CPM系统性能的多种信号参数进行仿真与分析。基于此，本文研究了级联卷积码系统的编码与译码原理，在给出软输入软输出译码算法推导的基础上，设计了编码与CPM的串行级联系统(Serially Concatenated Continue Phase Modulation, SCCPM)，编码类型包括卷积码和Turbo码，进一步利用扩展Turbo译码器能够同时输出系统位软信息和校验位软信息的特点，提出了基于扩展Turbo译码器与CPM串行级联系统的二次迭代译码算法，该算法有效利用了扩展Turbo译码器与CPM译码器之间的软信息，降低了信息传输过程中的损失，通过对Turbo-CPM系统采用传统译码算法与二次迭代译码算法的仿真与分析，得出结论：二次迭代译码算法在复杂度仅增加一次迭代的基础上，提高了系统的误码性能，保证了传输的可靠性。

       针对多径干扰的问题，本文引入单载波频域均衡技术(Single Carrier Frequency Domain Equalization, SC-FDE)，与多载波技术相比，该技术不易受到频偏的影响且具有较低的峰均比，在研究了CPM信号的Laurent分解及其次优化检测算法的基础上，设计了基于Laurent分解的SCCPM信号的SC-FDE系统，通过仿真分析可以看出该系统以较低复杂度达到了对抗多径干扰的目的。

       最后，本文对八进制CPM系统的调制及解调算法进行FPGA设计实现，联合仿真波形验证了设计方案的可行性与正确性，并分析了处理速率与资源占用情况，为高阶CPM信号的实际应用提供参考。

Ultra-short wave communication has the characteristics of high stability, strong survivability and low power transmitter, making it a popular choice in many wireless communication fields such as military communication and private broadcasting. The frequency band resources are becoming ever more scarce as modern wireless communication technology advances. For the ultra-short wave transmission system with limited communication bandwidth and power, on the one hand, it is considered to select excellent modulation mode and jointly adopt high-performance channel coding technology. On the other hand, it is necessary to consider how to combat multipath interference in wireless channels, so as to achieve efficient and reliable information transmission.

 

Based on the above background, this thesis focuses on CPM technique with high efficiency and spectral efficiency for waveform design, and implements FPGA design for high-order CPM modulation, providing support for the application of CPM based ultra-short wave transmission waveform.

 

Firstly, the key techniques of CPM are introduced in detail, including the definition and phase state of CPM signal. Using Rimoldi decomposition model of CPM signal, maximum likelihood sequence detection of CPM is deduced. And several signal parameters that affect the performance of CPM system are simulated and analyzed. Secondly, the encoding and decoding principle of concatenated convolution code system is studied. Based on the deduction of soft input and soft output decoding algorithm, a serial concatenated system for encoding and CPM is designed, in which the encoding types include convolution code and Turbo code. Further utilizing the feature that the extended Turbo decoder can output both the systematic bit soft-output and the parity bit soft-output at the same time, a quadratic iterative decoding algorithm decoding algorithm based on the extended Turbo decoder and CPM serial concatenated system is presented. The algorithm effectively utilizes the soft information between the extended Turbo decoder and CPM decoder, and reduces the loss of information transmission. Simulating and analyzing the Turbo-CPM system with both the traditional decoding algorithm and the quadratic iterative decoding algorithm, we arrive at the conclusion that the latter improves the bit error rate performance of the system and guarantees transmission reliability by only increasing complexity by one iteration.

For the problem of multipath interference, SC-FDE technology is introduced, which is not easily affected by frequency offset and has a low peak-to-average power ratio. On the basis of studying the Laurent decomposition of CPM signal and its suboptimal detection algorithm, the SC-FDE system of SCCPM signal based on Laurent decomposition is designed. Through simulation analysis, it can be seen that the system achieves the purpose of combating multipath interference with low complexity.

 

Finally, the modulation and demodulation algorithm of octal CPM system is designed and implemented with FPGA. Verification of the design scheme's feasibility and correctness is achieved through joint simulation, with the processing rate and resource occupation being analyzed to provid reference for the practical application of higher-order CPM signals.

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