Characteristics of transfer function of power lines having tapped branches in the propagation path

Power lines can be used for communication purpose. However, the channel is highly frequency selective arising from discontinuities in the network. In this work, the effect of tapped branches in different topologies (STAR and BUS) is studied. The frequency selectiveness is measured in terms of the Coherence Bandwidth. It is found that the Coherence Bandwidth is more for STAR than a BUS one. In STAR topology, the same at first decreases and then increases for increasing number of taps at the nodes. For large number of components, the transfer function of STAR branch is governed by the characteristics of the connecting cable while for in BUS topology, the same becomes very complex. The paper gives an idea of the dependency of the efficiency of the communication system on branches with different topologies encountered.