Patent ID: 8811529

Claim:
A transmitter circuit configured and arranged to communicate over power distribution lines that carry power using alternating current (AC) that operates at a power-line frequency, the transmitter circuit comprising: a data signal generation module configured and adapted to: select one of a plurality of carrier frequencies; and modulate a carrier signal, having the selected one of the plurality of carrier frequencies, to encode data bits to produce a first data signal; a signal strength module configured and arranged to adjust a signal strength of the first data signal to produce a second data signal over a range of signal strength values to compensate for degradation of a coupling capacitor over time; a coupling circuit configured and arranged to communicatively couple, using the coupling capacitor, the second data signal from an amplifier circuit to the power distribution lines and to filter the power-line frequency; a current sensing circuit configured and arranged to sense current provided to the power distribution lines by the coupling circuit; and a signal level control module configured and arranged to adjust a signal strength value of the signal strength module in response to the second data signal and the sensed current; wherein the signal level control module is configured and arranged to adjust the signal strength value by performing steps including: setting the signal strength to a default one of the signal strength values; and in response to the sensed current being less than a reference current, setting the signal strength to a higher one of the signal strength values; and wherein, in response to a configuration command indicating a threshold current, the signal level control module is configured to store the threshold current as the reference current.