Carrier Gain Adjustment for Improved Power-Line Signal-to-Noise Ratios

This paper describes carrier gain adjustment (CGA) in the CENELEC A-band, a counter-measure against the negative impact of a transmitter coupling circuit´s filter characteristic in this band. The performance of orthogonal M-FSK (M-ary frequency shift keying) without coding in the presence of white noise, is used as measuring rod. Due to the frequency response of the transmitter coupling circuit, different symbol carriers (of different frequencies) are exposed to different attenuation factors. As the CENELEC A-band lies very close to the power waveform frequency, a steep -40 dB/decade filtering slope is present in the lower parts of this band. Therefore, through linear amplification, only the least attenuated carrier can be amplified to the maximum level allowed by regulations, whilst the other carriers will be transmitted below the maximum level. Conversely, all carriers are exposed to the same noise levels present on the power-line. Carrier gain adjustment (CGA) however, counters the unequal attenuation effect of the transmitter coupling circuit, by amplifying those carriers more, which would suffer greater attenuation. Thus carrier gain adjustment is directly linked to the frequency response of the transmitter coupling circuit, and therefore said circuit response needs to be characterized before implementing CGA. This study shows that with these limitations in place, carrier gain adjustment proves successful in equalizing the attenuation effect of the transmitter coupling circuit and thereby equalizing and improving channel signal-to-noise ratios