摘要
失真度测量常采用基于快速傅里叶变换(FFT)的频域方法和基于曲线拟合的时域方法。FFT法需对被测信号进行整周期同步采样以避免栅栏效应和频谱泄漏,曲线拟合法计算量较大且拟合效果不易保证。为克服FFT法与曲线拟合法的上述不足,利用离散时间傅里叶变换(DTFT)提取被测信号基波分量并将其从时域波形中剔除,从而实现全谐波失真(THD)的计算。该方法无需进行曲线拟合或FFT,简化了计算流程。在12bit采样精度下对该方法进行了数值模拟与实验测试,对低失真正弦信号进行数值模拟得到的失真度绝对误差低于0.05%,而对20 Hz^20kHz方波和三角波实测所得失真度绝对误差小于1%,表明此方法能够便捷、可靠地实现失真度的测量。
The most frequently used methods for distortion measurement are fast Fourier transform（FFT）in frequency domain and curve fitting in time domain.However,FFT-based method needs integral period synchronous sampling,in order to avoid picket-fence effect and spectrum leakage.On the other hand,curve-fitting-based method has higher computational burden,and it is difficult to ensure the robustness.To overcome the above shortages of FFT-based and curvefitting-based approaches,discrete-time Fourier transform（DTFT）can be used to extract and eliminate the fundamental wave from the measured signal,and then the total harmonic distortion（THD）can be calculated.Neither curve fitting nor FFT is needed in the proposed method,thus the computation is simplified.Numerical simulation and experiment for the proposed method are performed with 12 bit sampling resolution.Simulation results of sinusoidal signal with low distortion show that the absolute error of THD is less than 0.05%,while the experiment results of 20Hz^20kHz square and triangle waves have less than 1%absolute error.Therefore,the proposed method is efficient and reliable for distortion measurement.
出处
《国外电子测量技术》
2017年第1期27-30,共4页
Foreign Electronic Measurement Technology
