【摘要】 在VLBI(VeryLongBaselineInterferometry)数据采集终端中,用数字滤波代替模拟滤波有其显著的优势。本文首先介绍了国外在VLBI数据采集终端中采用数字滤波的进展情况,然后阐述了数字滤波在系统中的实现方案。实现数字滤波的关键是信号处理的速度,降低运算量是实现快速处理的关键,本文给出了实现FIR数字滤波器的3种结构,并在运算量方面进行了分析和比较。在这基础上,还对数字滤波的2种系统实现方案进行了具体分析。高性能的FPGA(FieldProgrammablegateArray)芯片是实现数字滤波器的较好选择,文章最后给出了基于FPGA芯片、用查表(LUT:LookUpTable)的方式实现的数字滤波系统框图。更多还原

【Abstract】 A digital filter for bandwidth selection has obvious advantages on VLBI (Very Long Baseline Interferometry) data acquisition compared with the analog filter. This paper first reviews the development of digital filtering on VLBI data acquisition in Japan and NRAO (the National Radio Astronomy Observatory), then proposes two kinds of systematic implementation of digital filtering. The key factor to implement a filter is the speed of processing signals because of many highspeed arithmetic operations required. Reducing the computation time of digital filtering is important.The filter utilizes RAM lookup tables for tap weight multiplications. Three kinds of structures to realize the digital filter are compared here. Afterwards, the two kinds of systematic implementations are discussed in detail. With a steady advance in the technology of very highdensity VLBI integrated circuits in recent years, FPGAs (Field Programmable Gate Array Integrated Circuits) are developed fast and have been proved to be powerful in many fields of digital signal processing. Finally, this paper gives a hardware layout to implement digital filtering based on FPGAs.更多还原