基于预失真算法的任意波形发生器校准的研究

任意波发生器由于其可编程生成任意信号的特性,是信号与系统研究中的常用理想信号源,对其进行可溯源的校准是非常重要的。构建了由任意波形发生器、电缆、转接头、数字示波器和计算机组成的校准系统,采用预失真算法实现了对任意波形发生器的可溯源校准。预失真校准方法是基于补偿的思想,首先加载一个仿真的理想信号到任意波形发生器,由示波器进行可溯源测量,测量的信号包含了任意波形发生器和传输器件的失真,这个失真可以通过测量信号与理想信号的差值计算出来,根据这个失真对加载到任意波发生器的理想信号进行调整,最终实现了任意波形发生器的可溯源校准,使输入到示波器的信号成为一个理想信号。这是一个迭代过程,设计了迭代结束条件,即直至接近数字示波器的测量精度为止。为了验证校准方法的有效性,将50个等幅恒相的正弦波叠加而成的合成信号加载至任意波形发生器,经3次迭代,其相对误差的最大值从10.408 9%减小到2.305 3%。这表明研究的校准方法是有效的,校准后的任意波形发生器信号源系统可作为一个标准信号源,用于测量仪表的校准。

Research on calibration of arbitrary waveform generator based on predistortion algorithm

Because of the characteristic of generating any signal programmatically, the arbitrary waveform generator is an ideal signal source in the study of signal and system, so it is very important to traceable calibration. In this paper, a calibration system consisting of arbitrary waveform generator, cable, adapter and digital oscilloscope is constructed. The traceable calibration of arbitrary waveform generator is realized by using predistortion algorithm. The predistortion calibration method is based on the idea of compensation. Firstly, a simulated ideal signal is loaded to arbitrary waveform generator, which can be traced by oscilloscope. The measured signal contains the distortion of arbitrary waveform generator and transmission device. This distortion can be calculated by the difference between the measured signal and the ideal signal. According to this distortion, the ideal signal loaded to arbitrary waveform generator is adjusted, and finally it is realized that the traceable calibration of arbitrary waveform generator, and makes the signal input to oscilloscope become an ideal signal. In practice, this is an iterative process. In this paper, the condition of the end of the iteration is designed, that is, until it is close to the measurement accuracy of the digital oscilloscope. In order to verify the validity of the calibration method, this paper loads 50 sine waves of equal amplitude and constant phase into arbitrary waveform generator. After three iterations, the maximum relative error is reduced from 10. 408 9% to 2. 305 3%. This shows that the calibration method studied in this paper is effective. After calibration, the signal source system of arbitrary waveform generator can be used as a standard signal source for the calibration of measuring instruments.