中文摘要：

我国正在建设500m口径球面射电望远镜（FAST）,为了能够充分发挥自身口径大的优势,确保望远镜在世界上的领先,将自主研发世界一流的超宽带通用型数字后端（CRANE）。在整个CRANE开发中,硬件部分通过与中科院自动化研究所的合作,不仅开发了现场可编程门阵列（FPGA）运算板FDB（FAST Digital Backend）,还开发了3 Gbits/s 12 bits的宽带高精度模数转换电路板（ADC）芯片,并用此实现3 GHz带宽的一次性覆盖。此超宽带通用型数字后端同时也包括开发模拟信号前端电路板（AFB）。固件部分,目前研制者计划在FDB上实现百万级通道频谱仪——CRANE项目将优化FFT,研究级联式FFT来实现大点数FFT。一级FFT运算单元的分辨率可能会造成最终频点输出时信号失真,通过在Matlab上进行级联FFT算法仿真,研究了信号失真的情况,并用Matlab模拟还原出真实信号。

英文摘要：

The National Astronomical Observatories of the Chinese Academy of Sciences（NAOC） will soon finish the Five-hundred-meter Aperture Spherical Radio Telescope（FAST）,which will be the most sensitive single-dish radio telescope in the low frequency radio bands between 70 MHz and 3 GHz. To take advantage of its giant aperture, the ongoing selfdeveloping brand-new broadband receiver China Reconfigurable ANalog-Digital back End（CRANE） is expected to ensure that it would achieve the best possible overall performance.In hardware, CRANE includes developed parts — FAST Digital Backend（FDB）, 3Gbits/s, 12-bit Analog-to-Digital Converter（FAST3212ADC） — and developing part —Analog Front-end Board（AFB）. In its firmware, FPGA-based digital signal processing algorithms such as Digital Down Converter（DDC） and Fast Fourier Transform（FFT） will be applied to realize channelization on FDB. CRANE plans to build million channel spectrometer which measures a frequency precisely on FDB. We utilize two cascaded FFT to optimize the FFT for large-scale operation. However, the resolution of the first FFT unit would cause the distortion of the output results. The simulation on Matlab shows that final frequency can be restored.