| 摘要 |
PURPOSE:To reduce slope overload distortion without increasing quantized noises and instability of the system by applying differential coding to a sample value at the 1st differential quantizing circuit at the coder side, applying differential coding to the error at the 2nd differential quantizing circuit and adding and decoding two codes at the decoder side. CONSTITUTION:When an input signal Xn is normal and a COD1 can follow up the Xn, since an output I1(n) becomes an intermediate code word, an output (e) of a logical circuit L21 goes to ''0'', the quantizer Q2 codes only simply whether the value of the quantized error QEn is positive or negative and the quantization of 4 bits is attained equivalently. When the signal Xn is not normal, an output 11(n) keeps the transmission of maximum code word. In this case, a signal S2 becomes a value where the value just before the signal (e) goes to 1 is taken as the initial value and the coefficient S4 is multiplied by amultiplier M1, and a COD2 becomes an adaptive delta modulation circuit following up the value of the quantized error QEn of the COD1. The slope distortion generated by the COD1 is corrected by the COD2 until the output I1(n) takes a value other than the maximum code word. Decoders DEC1, 2 are constituted in the decoder side in correspondence to the COD1, 2. |
