| 摘要 |
PURPOSE:To perform the multilevel encoding modulation which is applied to 2<m>-value orthogonal amplitude modulation (m>=4 and (m) is an integer) and always enables correct decoding regardless of phase uncertainty. CONSTITUTION:A level 1 does not have an influence upon the decoded result when the phase difference of carrier waves is 180 deg.; but when the phase difference is + or -90 deg., the level 1 is inverted in an inverter 230 by the control signal from a second decoder 250 because it can be decoded but the decoded result is inverted. Since a level 2 cannot be correctly decoded when the phase difference is + or -90 deg., this phase difference is detected the second decoder 250 by means of information indicating the occurrence of error, and the phase of the input signal to the second decoder and a discriminator 270 of a non-encoded level is rotated by 90 by a phase shifter 240. The influence of phase rotation is eliminated by difference converters 130 and 260 with respect to the decoded result for 180 phase difference. |
