LPLC通信中双伪码扩频系统解调算法的研究与实现

发布时间：2018-09-14 20:49

【摘要】：低压电力线通信(Low-voltage Power Line Communication)是指以低压(220/380V)配电线路为通信介质进行数据传输的通信技术。电力线载波通信技术可以利用现有的电力网络,不需要额外线路铺设,省去了其他通信方式的布线过程,应用前景十分广阔。但是电力线主要功能是输电,而不是通信,所以网络复杂,信道环境非常恶劣,目前电力线通信技术的实际应用效果不理想。因此,需要根据我国电力线信道特性,设计一套适合我国电力线环境的载波通信系统,实现可靠的电力线通信。本文通过对常用的电力线通信技术的性能和实现成本进行深入研究,并结合我国复杂的电力线信道环境,决定采用新颖的双伪码扩频技术来实现低压电力线载波通信。本文的研究重点主要包括：双伪码扩频技术的调制解调原理、双伪码的码型选择、改进的数字匹配滤波器、自适应门限算法以及同步算法的优化等。本文对双伪码扩频技术的解调方法进行了深入研究,得出采用相关器的正交接收机在PN码较短的情况下解调性能要优于包络检波器；针对传统双伪码数量有限,性能不佳的问题,提出了一种改进的m序列对作为双伪码；为了实现高效快速的PN码捕获,本文将正交采样技术与并行匹配滤波器相结合,设计了一种改进的匹配滤波器；为了适应时变信道环境中信号衰减和噪声干扰的动态变化,在保证虚警概率一定的前提下使得检测概率最大,本系统应用信号估计的相关理论来实现自适应门限同步检测,提高通信系统的解扩性能；为了减少计算复杂度,在硬件实现过程中采用迭代算法,使同步计算量得到优化,降低了系统硬件成本。本文在Matlab/Simulink环境下搭建了一个采用上述关键技术的LPLC双伪码扩频系统仿真模型,然后对系统进行仿真和性能分析,验证了系统方案的可行性。在此基础上采用dsPIC33FJ256GP710芯片实现系统收发两端的主要算法,并设计了功率放大、耦合、谐振等外围电路,实现对片外信号的处理。最后,在不同测试环境下对系统进行测试。测试结果表明,所搭建的LPLC双伪码扩频通信系统能够实现可靠通信。
[Abstract]:Low voltage power line communication (Low-voltage Power Line Communication) is a communication technology which uses low voltage (220 / 380V) distribution line as communication medium. Power line carrier communication technology can make use of the existing power network and does not need to lay extra lines, thus eliminating the routing process of other communication modes, so the application prospect is very broad. But the main function of power line is transmission, not communication, so the network is complex, the channel environment is very bad, the actual application effect of power line communication technology is not ideal. Therefore, it is necessary to design a carrier communication system suitable for China's power line environment according to the characteristics of power line channel in China to realize reliable power line communication. In this paper, the performance and implementation cost of the commonly used power line communication technology is deeply studied, and combined with the complex power line channel environment in China, it is decided to adopt a novel dual pseudo code spread spectrum technology to realize the low voltage power line carrier communication. The emphasis of this paper is mainly on the modulation and demodulation principle of dual pseudo code spread spectrum technology, the code type selection of double pseudo code, the improved digital matched filter, the adaptive threshold algorithm and the optimization of synchronization algorithm, etc. In this paper, the demodulation method of dual pseudo code spread spectrum technology is deeply studied, and the demodulation performance of orthogonal receiver with correlator is better than that of envelope detector when PN code is short. In order to realize efficient and fast PN code acquisition, an improved m sequence pair is proposed, which combines orthogonal sampling technique with parallel matched filter to design an improved matched filter. In order to adapt to the dynamic changes of signal attenuation and noise interference in time-varying channel environment, the detection probability is maximized under the premise of constant false alarm probability. The system applies the theory of signal estimation to realize adaptive threshold synchronous detection. In order to reduce the computational complexity, the iterative algorithm is used in the hardware implementation, which optimizes the synchronous computation and reduces the hardware cost. In this paper, a simulation model of LPLC dual pseudo code spread spectrum system using the above key technologies is built in Matlab/Simulink environment. Then the simulation and performance analysis of the system is carried out to verify the feasibility of the system scheme. On this basis, the dsPIC33FJ256GP710 chip is used to realize the main algorithms of both ends of the system, and the peripheral circuits, such as power amplifier, coupling, resonance and so on, are designed to process the off-chip signal. Finally, the system is tested in different test environments. The test results show that the LPLC dual pseudo code spread spectrum communication system can realize reliable communication.
【学位授予单位】：福州大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN914.42

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