【作者】 文玥；

【导师】 张晓霞；

【作者基本信息】 电子科技大学 ， 光学工程， 2012， 博士

【摘要】 超宽带（UWB）通信凭借超宽的频谱带宽（3.1GHz~10.6GHz）和高速率的数据传输，已广泛应用于短距离的无线通信系统中。为了增加信号的传输距离和覆盖面积，光纤以其独特的优势成为解决长距离超宽带通信的方案。光纤作为一种高效的传输介质，不仅可以实现GHz量级信号的宽带传输，而且具有低损耗、抗干扰等优势。基于光纤传输的超宽带通信（UWB over Fiber）结合了光纤通信与超宽带通信的优势，在未来的高速宽带无线通信系统中具有重大的应用价值。本文研究了基于Mach-Zehnder（M-Z）电光调制器外调制的UWB无线接收系统。该系统实现了跨度7GHz的超宽带无线信号的接收，将接收到的UWB信号利用M-Z电光调制器转换成光信号，最后实现UWB无线信号的光纤传输。本文研究分为两大部分：高速电光调制器理论研究和UWB接收系统的研究与实现。高速电光调制器的理论研究主要从光波导和电极结构两个方面对高速电光调制器进行分析研究。光波导的研究方面，采用等效折射率法（EIM）和有限差分束传输法（FD-BPM）进行仿真与优化，研究了两种非对称M-Z结构的电光调制器，利用光学方法实现了M-Z电光调制器π/2的初始相位偏置。电极结构的研究方面，以单层结构Wheeler变换为基本模型，研究了多层介质的Wheeler扩展变换，得到了电极特征参数与电极结构参数的表达式，该方法与有限元法的计算精度相当，但提高了计算速度。本文首次提出了补偿层型微带线（MSL）电极模型、补偿层型共面波导（CPW）电极模型和屏蔽层型CPW电极模型。通过对电极和光波导结构的分析，使得调制器可达到阻抗和速率的同时匹配，理论实现高速和宽带宽的调制。UWB无线接收系统分为两个子系统进行研究，一是UWB天线系统，二是UWB接收系统。第一子系统从天线的基础理论进行分析研究，对矩形贴片天线的电流分布仿真，将贴片形状进行改进，设计并制作出了UWB天线，实测带宽可达到3GHz~14GHz，符合UWB天线的定义标准（3.1GHz~10.6GHz）。第二子系统采用超外差式结构，对UWB天线接收到的UWB信号进行滤波、放大和混频处理，重点优化了低噪声放大器和低通滤波器。根据实测结果，实际制作的UWB接收系统的接收频段达到了UWB频段要求，实现了灵敏度为-80dBm的信号接收。本文最后搭建了UWBoF通信实验系统。UWB信号经过制作的UWB接收系统后，将其输出的中频信号加载到电光调制器的调制电极上，同时将光信号接入电光调制器的光源端口，使加载了UWB信号的光波通过光纤传输，实现了UWB信号的光调制。测试结果表明：UWBoF通信系统成功实现了超宽带频段（3GHz~10GHz）的高频信号接收；当载噪比为40dB时，该系统的灵敏度为-80dBm；该系统调制输出曲线的半波电压为3.9V。更多还原

【Abstract】 Ultra-wideband (UWB) communication systems, with the ultra-wide bandwidth(3.1GHz~10.6GHz) and the high-speed data transmission, have been wildly used in theshort distance wireless communication systems. In order to increase the signaltransmission distance and coverage area, optical fiber is the powerful solution toprovide the long-range UWB communications, with the advantages including GHzbroadband transmission, low loss and no channel crosstalk. UWB signals transmit overfiber (UWBoF) technology has great value in high-speed broadband wirelesscommunication system in the future.In the paper, the UWBoF communication system based on Mach-Zehnder (M-Z)modulator is designed and implemented. In this system, the wireless signal of bandwidth with7GHz has been received first, and then this received UWB signal isconverted into optical signal by Mach-Zehnder modulator, finally, the UWB signaltransmitted over fiber has been implemented. Two main parts are studied: one is thetheoretical study of the high-speed electro-optic (E-O) modulator, another is the studyand implementation of the UWB receiver system. In the theoretical study of themodulator, optical waveguide and electrode have been analyzed. The effective indexmethod (EIM) and finite difference-beam propagation method (FD-BPM) are used tosimulate and optimize the optical waveguide structure. Two structures of theasymmetric M-Z modulators are designed which can make the initial phase differencereach π/2. The expressions of the electrode characteristic and structure parameters areobtained by the extended multilayer wheeler’s function. In the comparison with finiteelement method (FEM), the extended multilayer wheeler’s function has the samecomputational precision, but has higher computational efficiency. The compensationlayer of the microstripe line (MSL) electrode structure, the compensation layer of thecoplanar waveguide (CPW) structure and the multilayer CPW structure with shield areput forward for the first time. Combining with the optimized results of the waveguideand the electrode, the velocity matching and the impedance matching for the E-O modulator can be both achieved simultaneously, so the modulator could get thehigh-speed and wide bandwidth modulation.UWB wireless receiver system is divided into two sub-systems, one is the designof the UWB antenna system, and the other is the investigation and implementation ofthe UWB receiver. For the first sub-system, by analyzing and simulating the currentdistributions of rectangle patch antenna, an improved patch structure is given, and a newUWB antenna is implemented. The measurement of the band width for the implementedantenna can achieve3GHz~14GHz, which can match the standard3.1GHz~10.6GHzdefined by Federal Communications Commission (FCC). For the second sub-system,according to the UWB frequency ranges, the UWB receiver based on thesuperheterodyne structure is studied, including design and implementation of thelow-noise amplifier and low pass filter structure. In our experiment, the receivingsensitivity of the UWB receiver can achieve-80dBm when the CNR is around40dB.Finally, the UWB over fiber experimental system is established successfully. Afterthe UWB signal is processed by the UWB receiver, the output signal is transmitted intoRF port of the E-O modulator, meanwhile, the optical signal is input to the opticalsource port. The UWB signal has been carried by optical wave and transmitted byoptical fiber. The experiments show that the UWBoF receiving system can achieve largebandwidth reception, which can match the standard of UWB signal. The receivingsensitivity of our system is around-80dBm, when the CNR is around40dB, and thehalf-wave voltage is about3.9V.更多还原