示波器输入端口阻抗频率特性矢网测量方法

Measurement method of impedance-frequency characteristics at the oscilloscope input port with vector network analyzer

示波器输入阻抗的传统测量方法所得测量结果为:直流电阻、输入电容,不能获取阻抗的频率特性。因此,由这种"静态"测量方法所得的测量结果是示波器输入阻抗的片面反映。本文提出用HP8752A矢量网络分析仪测量示波器输入阻抗的方法。整个测量过程均是在示波器通电工作状态满频带正弦信号激励下实现的。复阻抗一频率特性在史密斯圆图上表现得十分清楚。依据复阻抗在10 MHz,20 MHz频点的相关电抗数据,可求得示波器输入电容。由HP8752A测得的结果,能客观、全面地反映示波器输入阻抗的高频段(10 MHz～100 MHz)特性。

Using traditional method of measurement we can obtain oscilloscope input impedance results, one is DC resistance datum, the other is input capacitance datum. Impedance-frequency characteristics can not be obtained by traditional method. Therefore, the result of measurement by traditional＂static＂ measuring method is one-sided reflection of oscilloscope input impedance. This paper introduced a new method using HP8752A vector network analyzer to measure oscillo- scope input impedance. The whole measuring procedure is accomplished with the oscilloscope being power on and in its full frequency range sine signal excited state. The complex impedance-frequency features are displayed clearly by Smith chart on the screen of HP8752A. According to the measured reactance data at 10 MHz and 20 MHz, the input capacitance of oscilloscope can be obtained. The result of measurement with HP8752A can reveal high- frequency range （10 MHz-100 MHz） features of the oscilloscope objectively and completely.