Transmission Line Theory Applied to Digital Systems
Microstrip Transmission Line Techniques Evaluated Using TDR Measurements
11-28
TDR Example 4
Experiments have also been performed to determine the effects of a ground
plane on the characteristic impedance of microstrip lines. Figure 11-13
illustrates what happens when the ground plane width under the transmission
line abruptly drops to the width of an active line. The TDR waveform shows
that a 12% reflection occurs due to this discontinuity in the ground plane.
Using equation 15 the impedance of the 2½ inch-long strip can be calculated as:
Figure 11-13
Effects of Ground Plane Discontinuities.
Z
line
10.12+
10.12–
-------------------
50• 68ohms==
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