Development Of PXI Bus Digitizer

The digitizer can digitize the dynamic analog signal and analyze its time and frequency domain character through processing the acquisitioned data. It can be applied to lots of fields. PXI bus is the extension of PCI bus for instrument. It combines the advantages of PCI bus and CompactPCI. More and More manufacturers begin to support PXI bus, meanwhile it's getting much popular in the world. Therefore, it means much to develop the digitizer based on PXI bus.To establish the whole scheme of digitizer, the design studies the implements of different products based on many articles and product descriptions, and compares the advantages and disadvantages comprehensively. The digitizer based on PXI bus uses FPGA (Field Programmable Gate Array) to implement 256 points, radix-2 DIT FFT (Fast Fourier Transform Algorithm). The design uses pipelining for FFT processing and can accomplish sampling and processing signals of two channels at the same time.In the signal acquisition circuit,Σ-ΔA/D convector is used to enhance the precision of the signal sampling. The fuctions of impedance matching, over voltage protection, AC/DC coupling and amplification/attenuation in the analog circuit are designed to enhance the reliability and testing precision of the module. Meanwhile, the digitizer module has large capacity SDRAM for storage. The SDRAM controller is implemented by FPGA, which can be flexibly changed according to need. In the part of software, a software panel and driver are designed for the user to control the digitizer.The test results proved that the design of the project is correct. The processing time of 256 points FFT is only several microseconds. The error value of the test results is within 10-2 compared to the theory value calculated by Matlab.