Bus with Attenuating Probes: In measuring signals on high-speed lines, it is common practice to use an attenuating probe. as illustrated in Figure 3-58. A 50-Q transmission line with a 950-Q series resistor taps the signal with a 20: 1 attenuation while providing a negligible ( l kQ) load to the line. Show how such a probe can be used to design a bus that has no reflections from the stubs (as in Exercise 3-7). Give a formula that relates how the attenuation of the probe stubs can be traded off against the attenuation of a signal traveling along the bus.
Buses With ont Stubs: One can build a bus (multi-drop transmission line) in which there are no reflections off the stubs by placing matching networks at each drop across the line, as shown in Figure 3-57. 19 Design the resistive matching network, N, shown in the figure so that a signal transmitted to the network from any of its three terminals is propagated out the other two terminals (possibly attenuated) with no reflections.
With the impedance values shown in the figure, 20-Q bus and 100-Q stubs, how much energy is Jost from the signal traveling down the bus at each stub? How much energy would be lost if both the stubs and the bus were 50-Q lines?