Design of a Broadcasting Modem for a DC PLC Scheme

A new type of power line carrier communication (PLC) technique is developed to reduce cable requirements for robotic and vehicular systems. An electrical line connecting a dc power supply to motor drives and sensor units is used for transmitting data as well as for delivering the dc power. Unlike conventional ac power line communication, the dc power bus has predictable noise and impedance characteristics that allow for large fanout and high bandwidth. First, the basic architecture of the dc power line communication is presented. Then, a design of a high-fanout modem that uses a Guanella-type transmission line transformer (TLT) is presented. The serial windings and special resonance characteristics of the TLT coupled with a capacitor are exploited to minimize attenuation in high-fanout systems. The modem characteristics including high-frequency parasitic dynamics are analyzed, and the end-to-end line impedance and signal gain are evaluated as the number of nodes goes to infinity. A prototype dc power line communication system is then built, tested, and applied to a design for modular reconfigurable robots