Dual Coupler for Dedicated Switching with Loads

Historically, unpredictable on-off switching of loads has been a major obstacle to power-line communications. Some researchers have gathered valuable data and have proposed statistical models in order to try and mitigate these sudden changes in access impedance. Others have proposed network conditioning in order to 'block off harsh loads from the power-line network by means of series filters. These filters are expensive, as they have to be rated at the typical current that is drawn by the load to be 'blocked off. Also, in many cases, these are the very loads than need to be monitored and controlled for home automation. This paper investigates the possibility of utilizing a simple, dual coupler to diminish the impact of switching loads on data transmission. First, the design of a suitable dual coupler is demonstrated, using a commercially available high-frequency transformer. Next, live 220-V measurements are done for 50-Omega modems at frequencies below 1 MHz. These live measurements confirm that the proposed dual coupler can aid in the optimization of a power-line network by means of( i) improved transmission when a certain network point is loaded and/or (ii) a more predictable (lower) power-line impedance level -facilitating more accurate impedance adaptation.