| 摘要 |
PURPOSE:To reduce the deterioration of the correction effect of a soft diciding error of a nonlinear system by weighting the threshold value intervals of A/D conversion to equal phase intervals and to attain the approximately optimum soft decision. CONSTITUTION:Both a digital phase modulated signal and noise are vector-displayed in the figure (a) when they passed through a linear transmission system and the figure (b) when they passed through a nonlinear transmission system, e.g., a limitter respectively. The space of the threshold value is not set equidistantly to the amplitude of the demodulated signal unlike a convertional case when the A/D conversion is applied to a superposition signal of the noise and the digital phase modulated signal passed through the nonlinear system. Instead the threshold value space of an A/D converter 4 is set so that the phase of a reception signal is set equidistantly on the phase surface as shown in the figure. In such a way, the soft decision having the reduced deterioration is possible even to a reception signal having a changed distribution of noise by supplying the equidistant weighting to the threshold value space of the converter 4 and through a nonlinear system. |
