【摘要】 采用基本窗函数和广义余弦窗函数对信号加权的谐波分析法可减轻非整周期截断对介质损耗因数tanδ测量的影响,但其效果受到窗函数固定旁瓣性能的制约。Kaiser窗可定义一组可调的窗函数,自由选择主瓣与旁瓣衰减之间的比重,因此能全面地反映主瓣与旁瓣衰减之间的交换关系。本文讨论了Kaiser窗的旁瓣特性,提出了基于Kaiser窗双谱线插值FFT的tanδ测量方法,运用多项式拟合求出了实用的插值修正公式,推导了信号初相角及tanδ的计算式。仿真结果表明,Kaiser窗函数抑制频谱泄漏效果好,基于Kaiser窗的双谱线插值FFT方法克服了谐波干扰、基波频率波动、采样频率变动、采样时间长度变化及白噪声对tanδ测量的影响,且设计实现灵活,测量结果精确、稳定,可用于介质损耗因数tanδ的离线测量与在线监测。更多还原

【Abstract】 The harmonic analysis method based on fundamental windows and generalized cosine windows was used to eliminate the errors of dielectric loss factor tanδ measurement caused by non-integral period truncation,but the analysis result is restricted by the performance of the fixed side lobes of these windows.Kaiser window can be defined by a group of adjustable function and the specific weight between the major lobe and side lobes decay of Kaiser window can be freely selected,so the commutation relation between the major lobe and side lobes decay can be presented in the round.The characteristic of side lobes of Kaiser window is discussed in this paper,and an approach for tanδ measurement based on Kaiser window double-spectrum-line interpolation FFT is proposed.The applicable rectification formulas of the interpolation are obtained by using polynomial curve fit functions.The arithmetic expression of fundamental initial phase and tanδ is deduced.The simulation results show that Kaiser window function can restrains spectral leakage well,and the influences on tanδ measurement caused by harmonic,fundamental frequency fluctuation,sampling frequency and sampling time length in change and white noise are all overcome by using the approach presented in this paper.This approach can be designed and realized easily and has precise and steady results,which can be used in tanδ offline measurement and online monitoring.更多还原