基于微带延时线的皮秒脉冲测量

The measurment and the generation of ultrafast pulse are very important for fundamental research, engineering application and defence-related science and technology. For example, in the experiments of high-energy physics and astrophysics, the signals of events are of nanosecond-grade or even picosecond-grade risetime. A data acqusition system based on ultraspeed devices and microstrip delay line can meet the requirment very well for measuring such ultrafast transient electronic pulse with high accuracy and low cost. To use the microstrip line as a transmission and storage medium of a transient pulse, the pulse can be decomposed into several slower parts that can be converted by several ADCs in parallel. A data acqusition system dose not need very high-performance ADC/sampling gates by this method and can works well on measuring picosecond-grade or nanosecond-grade pulse. With the principle of real time sampling, this project will deliberate over the conditions refer to the ultrafast pulse transmission on microstrip line, the works of the sampling circuits and some problems of nonuniform sampling. So the theory of microtrip line, the design of circuits, the methods of digital signal processing and other problems when produce a real circuit will be studied in this project.

超高速脉冲信号的产生与测量对许多基础研究、工程应用和国防科技都十分重要。例如在高能物理和天体物理的实验中，事例信号的上升时间往往是纳秒级甚至是皮秒级的。基于超高速器件与微带延时线构成的数据采集系统非常适合于对此类超高速瞬态电脉冲信号的精确与低成本测量。采用微带线作为瞬态脉冲的传输与存储载体，信号可分解为慢速存在的各个部分，从而可以使用ADC进行并行的数据转换。这种方法降低了对ADC及采样门电路的要求，使系统可以达到测量纳秒至皮秒脉冲信号的水平。以实时采样测量为原则，本项目将仔细考虑超高速脉冲在微带线上的传输情况、采样电路的工作情况以及各种非均匀性采样问题。因此，微带线理论、电路的设计、数字信号的处理方法以及其他制作电路时的问题都将是本项目的研究对象。

尽管ADC器件的性能不断提高，采用并行交错采样技术仍然是高性能数据转换系统主要技术。国内对并行采样技术的研究大多集中在ADC系统的实现上，对于慢速ADC的带宽与高速信号带宽之间的匹配问题研究较少。在本项目中，用微带线作为瞬态脉冲的传输载体，通过在ADC前面插入的采样保持电路将信号分解为慢速存在的各个部分，使并行的慢速ADC可以实现高速的数据转换，并改善了系统的带宽性能。研究内容包括微带线的阻抗匹配、采样保持电路的带宽特性、ADC系统等。研究表明：采用宽度跳变的微带线，可以很好地实现信号传输的阻抗匹配，便于在并行采样系统中实现超高速信号的分配与延时；前级采样保持电路可以解决慢速ADC的带宽限制以及较宽的采样孔径带来的问题。更好的性能可以使用集成电路的制作工艺来获得。