【摘要】 用ＤＤＦＳ技术提供参考信号，以快速模拟开关取代乘法器件，加上四阶巴特渥斯低通滤波器构成了本选频电平表的混频环节。对中频信号采样转换，由ＤＦＴ分析直接得出信号幅值，由于在ＤＦＴ分析中采用了布来克曼－哈利斯三项系数窗，从而获得了带宽约为２Ｈｚ的窄带滤波效果。更多还原

【Abstract】 The mixing link of this selective level meter is made up of reference signals provided by DDFS technique,fast analog switches in place of multipliers and forthorder Butterworth lowpass filters.The medium fuequeney signals are sampled and converted.The signals amplitude is directly is obtained by means of DFT analysis.As BlackmanHarrith trinomial coefficient windows is adopted in DFT extension set,The narrowband filter with about 2 Hz is obtained.更多还原