Question

To measure the characteristics impedece of transmission lines using frequency domain

Answer 1

The characteristic impedance of the transmission line in high frequency domain was measured by TDR using sine wave. (calling “sine wave TDR method” here after.) The characteristic impedance value of 5m-long, 50Ω semi-rigid cable was measured almost as 50Ω by this method. On the other hand, that of the 28cm-long, 70Ω micro-strip line swung around 50Ω. As this cause it may be considered that the sine wave duration necessary for the measurement was not enough in case of 28cm line and It couldn’t be measured precisely by the visual observation. The characteristic impedance in the high frequency range could be measured by sine wave TDR method by using wide band width oscilloscope and high-speed switching IC in future.

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