SUMMARYA multiple-symbol differential detection scheme based on the ML criterion is adopted to MAPSK and the decision rule to estimate the transmitted signals is constructed theoretically, including terms for the channel noise power. SER performance of star QAM and (4,12) QAM, which are typical constellations for 16APSK, under the decision rule is evaluated. It is confirmed that the performance of this decision rule is better than that using the former rule. In addition, we introduce the (M,L) algorithm into this detection scheme to reduce tree search and confirm its performance by computer simulation. Finally, the performance shows good proximity to that of the ideal coherent detection on the AWGN channel.
SUMMARYThis paper proposes an earthing resistance measurement method for a simple earthing electrode without two auxiliary electrodes. The proposed method can measure the earthing resistance by evaluating loop impedance of an earth return circuit composed of an earth electrode of the under test and a lead wire, a return wire, and the earth soil. The return wire is placed on the soil surface without any terminations. The earthing resistance of the electrode of the under test can be given by the earth return circuit impedance at a resonant frequency design between 100 kHz and 1 MHz. The measurement conditions for the proposed method are determined by numerical calculations. Earthing resistance deviations between the proposed method and the existing method are -13% to +22% for earthing resistance values with 50, 100, or 300 Ω. It is found that the proposed method can be used to evaluate an earthing resistance around 100 Ω for a simple earthing electrode.
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