光子时域展宽辅助ADC的研究

发布时间：2018-05-20 20:36

本文选题：光子时域展宽辅助模数转换器 + 调制　；参考：《电子科技大学》2015年硕士论文

【摘要】：传统电模数转换器(Analog to Digital Converter, ADC)作为连接模拟世界和数字世界的桥梁,通常存在着以下一个或多个局限性：1.采样时钟的抖动；2.采样保持电路的渡越时间；3.比较器的速度(准确度)；4.晶体管阈值和无源组件的阈值的不匹配等。射频(Radio Frequency, RF)信号的频率越大,局限性就越明显。针对电ADC所存在的局限,研究者们做了大量的工作。但是,宽带系统中仅使用电域的数字信号处理(Digital Signal Process,DSP)对捕获超快、大宽带的信号受电子瓶颈的限制存在一定的局限。而基于光子时域展宽(Photonic Time-Stretch,PTS)辅助结构的光子时域展宽辅助模数转换器(Photonic Time-Stretched ADC,PTS-ADC)作为一种新型的电光ADC,将高速的RF信号进行降速预处理,以低于奈奎斯特采样率的速率捕获RF信号,可突破电子瓶颈的限制,实现对超高速、大宽带信号的处理。PTS-ADC通过以下几步完成：第一步,通过一段色散介质给光脉冲引入啁啾；第二步,电光调制器将快速的RF信号调制到啁啾光脉冲上,完成时间-波长映射；第三步,通过另一段色散更大的介质,完成波长-时间映射,同时RF信号在时域上被展宽,即速率被降低了；第四步,低速电ADC对时域展宽后的RF信号以低于奈奎斯特采样率的速率进行模数转换,恢复出原始的超快速信号信息。由于PTS-ADC中色散介质是决定采样率和输入带宽的重要因素之一。为此,本论文提出一种基于混合双轴芯和凹陷型包覆结构光子晶体光纤(hybrid structure of Dual-Concentric-Core and Depressed-Clad PCF, DCC-DEC-PCF)的高速PTS-ADC方案。借助DCC-DEC-PCF高色散值和低损耗的优势,PTS-ADC可获得更高的采样速率和输入带宽,而且引入损耗低、结构简单。本文介绍了PTS-ADC的基本原理,讨论了系统的噪声特性,完成了数学公式推导,建立了系统的数学模型,仿真了基于双边带(Double Sideband, DSB)调制和单边带(Single Sideband, SSB)调制的PTS-ADC的频率传输特性、谐波失真、残余相位失真、时间带宽积等,并进行了分析比较。另外,针对时域展宽后的RF信号光的信号功率小导致的探测难度大的问题,分析了相干探测及包络去除算法的方式探测及处理RF信号。
[Abstract]:As a bridge between analog world and digital world, traditional analog to digital converter Analog to Digital Converter, ADC) usually has one or more of the following limitations: 1. The jitter of the sampling clock. The transit time of the sample-and-hold circuit is 3. The speed of the comparator. The mismatch between transistor threshold and passive component threshold, etc. The greater the frequency of radio frequency, the more obvious the limitation. In view of the limitations of electrical ADC, researchers have done a lot of work. However, in wideband systems, only digital signal processing (DSPs) in power domain is limited to capture ultra fast and large wideband signals are limited by electronic bottleneck. As a new type of electro-optic Time-Stretched, the Photonic Time-Stretch-Based (PTS-based) Photonic Time-Stretch-Based (PTS-based) Photonic Time-Stretch-Based Auxiliary Converter (PTD), as a new type of electro-optic ADCA, preprocesses high speed RF signals to capture RF signals at a rate lower than the Nyquist sampling rate. It can break through the limitation of electronic bottleneck and realize the processing of ultra-high speed and large wideband signal. PTS-ADC is accomplished by the following steps: the first step is to introduce chirp to the optical pulse through a section of dispersive medium; the second step, The electro-optic modulator modulates the fast RF signal onto the chirped optical pulse to complete the time-wavelength mapping. The third step is to complete the wave-time mapping through another medium with greater dispersion, while the RF signal is broadened in time domain. That is, the rate is reduced, and in the fourth step, low-speed electrical ADC converts the RF signal at a rate lower than the Nyquist sampling rate to recover the original super-fast signal information. Dispersion medium is one of the important factors to determine the sampling rate and input bandwidth in PTS-ADC. In this paper, a high speed PTS-ADC scheme based on hybrid structure of Dual-Concentric-Core and Depressed-Clad PCF (DCC-DEC-PCF) is proposed. With the advantage of high dispersion value and low loss of DCC-DEC-PCF, PTS-ADC can obtain higher sampling rate and input bandwidth, and the introduction loss is low and the structure is simple. This paper introduces the basic principle of PTS-ADC, discusses the noise characteristics of the system, deduces the mathematical formula, establishes the mathematical model of the system, and simulates the frequency transmission characteristics of the PTS-ADC based on the double Sideband modulation and the single Sideband (SSBs) modulation. Harmonic distortion, residual phase distortion and time bandwidth product are analyzed and compared. In addition, aiming at the difficulty of detecting RF signal caused by low signal power, the methods of coherent detection and envelope removal algorithm are analyzed to detect and process RF signal.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN792

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