| 摘要 |
<p>PURPOSE:To measure the electric length of a transmission line without being influenced by a reflection on the way of the transmission line and a level variation standing wave, by separating a going-path signal and a return-path signal by executing a frequency conversion, and measuring the phase difference of the respective signals. CONSTITUTION:An outgoing-path signal generated by an oscillator 1 is inputted to a hybrid 3 through a low-pass filter 2. Its output signal is doubled by a doubler 5 through a transmission line to be measured 9 and a hybrid 4. The output signal of this doubler 5 is returned to the hybrid 4 through a band pass filter 6. The output of this hybrid 4 is led to a PLL loop filter 7 by the hybrid 3 through the transmission line to be measured 9 once again. A return-path signal doubled therein is brought to a frequency division and becomes a phase comparing signal. This phase comparing signals is compared with a reference frequency as to its phase, and the electric length of a cable to be measured and its variation are obtained.</p> |
