| 摘要 |
<p>PURPOSE:To make it possible to measure the characteristic impedance with high precision, by making an output impedance value small when an output is sent, and making the value sufficiently large before the output signal is returned to an output end. CONSTITUTION:A driving circuit 1 includes a means which switches the output impedance of the circuit 1 to a smaller value and a sufficiently larger value than characteristic impedance to be measured. Now, a short pulse signal is sent into a transmission line 3 to be measured from the circuit 1. The reflected wave from a far end is observed. The resistance value of a variable resistor circuit 4 is changed so that the resistance value as the reflected wave becomes the minimum wave may be the characteristic impedance of the line 3. A control signal is issued to the switching means of the circuit 1 from a control circuit 6. The output signal is sent to the line 3 from the circuit 1. At this time, the output impedance is made to be a smaller value than the characteristic impedance to be measured. The signal having a large amplitude is sent out. Before the reflected wave is returned to an output end, the output impedance is made to be a sufficiently larger value than the characteristic impedance to be measured. Thus the reflected wave is made large.</p> |
