Bidirectional bus coupler presenting peak impedance at carrier frequency

摘要

A bidirectional coupling circuit is provided for carrier based communication and control networks in which a coupling transformer is employed having relatively decoupled primary and secondary windings which are each tuned to the carrier frequency. Separate secondary windings are wound on the same core leg, one of these secondary windings being employed as a transmitter winding which is referenced to a positive supply voltage and the other winding being employed as a receiver winding which is referenced to ground. The coupling transformer is arranged to have a relatively high input impedance at the carrier frequency but due to series resonant effects has a relatively low impedance for undesired signals on either side of the carrier frequency. An operational amplifier is connected to the receiver winding to provide high gain amplification for a signal received from the common network power line without loading the other windings of the transformer. A transistor or FET is connected in series with the transmitter secondary winding to a positive voltage supply so that a relatively high amplitude transmitter signal is produced on the common power line.