基于FPGA的可调信号源检测装置的设计

Design of Adjustable Signal Source Based on FPGA for Inspection Device

本文针对涡流检测装置中所需的高精度可调信号源，提出了一种新的设计方法，即利用Attera公司FPGA芯片，用编程开发片内DDS模块产生数字可调正交信号，再经D／A转换和低通滤波成为可靠信号源。重点研究了系统设计原理、硬件构成和QuartusⅡ开发环境下使用VHDL实现片内累加器、波形表以及相位控制模块开发的具体方法。系统实际测试效果达到了较高的精度和稳定度，并具有双路频率连续可调、高宽带等特点，完全满足涡流检测系统的要求。此设计方法将DDS技术与FPGA相结合，可靠性、适应性较高，并较之使用成品DDS芯片显著降低成本，具有一定的推广价值和市场应用前景。

Aims with the high-precision adjustable signal source needed by the eddy current detecting device, this paper presents a new design method about the DDS signal generator which has two outputs with variable phase difference used in eddy current testing system. On the basis of Altera＇s FPGA chip, this method uses VHDL to develop an on-chip DDS module to generate the digital variable orthogonal signal and then the digital signal becomes a reliable signal source through D/A conversion and low-pass filter. The focus of research is put on the design principle, hardware composition of the system and the concrete method of realizing the de- velopment of on-chip accumulator,waveform table and phase control module by means of VHDL under QuartuslI development envi- ronment. The practical testing effect of the system shows that the system characterized with enhanced reliability and adaptability, higher stability and precision, and twin-channel frequencies can be adjusted continuously and high-speed wide-band, etc., it fully satisfy the requirements of the eddy current detecting system. Compared with using finished product DDS chip, this method notably reduces the cost by combining DDS with FPGA. And thus the system is of value of popularization and prospect of market application.