Phase‐diversity receiver using two pairs of three wires for data transmission over a low‐voltage distribution line

Abstract

AbstractIntensive efforts have been observed in recent years on the development of data communication technology, aiming at the effective utilization of such existing transmission lines as the in‐house distribution line. The automatic consumption meter reading, for example, uses the low‐voltage distribution line as the transmission channel.This paper aims at the improvement of the receiver demodulation performance in the data transmission using the low‐voltage distribution line and proposes the phase‐diversity reception using two phases (red and black) of the single‐phase, three‐wire system. In the data transmission using the low‐voltage distribution line, stray signals are produced between the two phases of the single‐phase, three‐wire lines and two signals with different signal‐to‐noise (SN) ratios are received. If a simple scheme such as the addition is employed, a problem arises in that the reliability of the demodulated data is deteriorated.To cope with this problem, this paper proposes a phase‐diversity reception, where the time‐varying phase difference is adjusted to zero using an adaptive phase shifter and the SN ratio is improved by synthesizing the two‐phase received signals. The proposed scheme is implemented on a digital signal processor (DSP), and a robustness against the channel noise and the periodic attenuation is realized by the feedback (FB) control.As a result of an experimental evaluation, it is shown that the SN ratio is improved by 2.7 dB at the maximum for the stationary phase error, compared to the traditional simple addition and the addition/subtraction selection schemes. Thus, it is verified that the receiver demodulation performance of the low‐voltage distribution line data transmission can be improved.