| 摘要 |
<p>The test instrument is used to perform both time domain reflectometry (TDR) and analysis of transmission signals on a line under test. Further, the test instrument provides for both pulse TDR and step TDR. A coupling transformer having an enhanced low frequency response provides for coupling of the test instrument to the line under test. Isolation circuits between the coupling transformer and the line under test to prevent damage to the test instrument due to voltages on the line under test allow the test instrument to be used in connection with an active line under test. Two isolation circuits are utilized to maintain longitudinal balance of the circuit. During step TDR, the positive and negative transmitter circuits provide step-shaped impulse signals. The enhanced low frequency response of the coupling transformer allows for transmission of step-shaped impulses, including the DC components of those signals, to the line under test and allows for transmission of reflected signals, including the DC components of those signals to the receivers. The test instrument provides selectable impedance matching and provides for selectable attenuation levels.</p> |
