| 摘要 |
The length and attenuation of a signal line between a transmitter and a customer premises equipment is to be estimated. A frequency dependent line input impedance (Z in,(f)), as seen from the transmitter, is measured and an absolute impedance value (ae Zin,(f) ae) is generated. The latter is shown as a curve (Al) in the diagram with the frequency (f) on the abscissa and the impedance (ae Zin,(f) ae) on the ordinate. Extreme values (Max.l, Max2, Max3; Minl, Min2, Min3) are denoted and a frequency distance (FD1- FD4) between two consecutive of the extreme values is generated. The line length (L) is generated as L=1/2 . vop/FD1, in which vop is the velocity of propagation of a signal on the line. The attenuation is estimated by multiplying the line length with an average attenuation value for the actual line type. The advantages are that the line length can be estimated with good accuracy in a simple manner for short lines and that the line attenuation is estimated in a simple manner.
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