feat(matlab): comm lab 5 half

Matlab/comm/lab5_0.m

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+clc
+%================================================
+%已知抽样值以△为单位
+%================================================
+x = 2047                        %抽样值/量化单位△
+pcmcode = pcmEnCode(x)                %调用pcmCode()函数实现PCM编码
+amp = pcmDeCode(pcmcode)            %调用pcmDecode()函数实现PCM译码
+amp = pcmDecode(pcmcode)
+%qerror = x-amp                      %求量化误差
+%================================================
+%已知抽样值为实际电压值，则需先转换为以△为单位
+%================================================
+% M = 5;                              %设置量化范围 -5~+5
+% delta = M/2^11;                     %求量化单位△
+% y = +2.5                              %设置抽样值/V
+% y0 = round(y/delta)                 %将抽样值转换为以△为单位
+% pcmcode = pcmCode(y0)                %PCM编码
+% amp=pcmDecode(pcmcode);             %PCM译码
+% amp = amp*delta                     %转换为实际电压值
+% qerror=y-amp                       %求量化误差
+
+
+function pcmcode = pcmEnCode(s)
+    start_t=[0,2.^(4:11)];
+    width_t=[1,1,2,4,8,16,32,64];
+    pcm=0;
+    if s>0 
+        pcm=pcm+bitshift(1,7);
+    else
+        s=abs(s)
+    end
+    for i = 0:7
+        if s < start_t(i+2)
+            pcm=pcm+bitshift(i,4);
+            pcm=pcm+floor((s-start_t(i+1))/width_t(i+1));
+            break
+        end
+    end
+    pcmcode=dec2bin(pcm,8);
+end
+
+function amp = pcmDeCode(pcmcode)
+    start_t=[0,2.^(4:11)];
+    width_t=[1,1,2,4,8,16,32,64];
+    code=bin2dec(pcmcode);
+    isNeg=0;
+    if code < 128
+        isNeg=1;
+    k=bitshift(bitand(code,0b01111111),-4);
+    amp=start_t(k+1) ...
+       + double(mod(bitand(code,0b01111111),16)) ...
+       * width_t(k+1);
+    if isNeg=1 amp=-amp;end
+end
+
+%PCM译码函数
+function amp = pcmDecode(pcmcode)
+    code_table=[0,2.^(4:11)];           %段落起始电平表
+    delta=[1,1,2,4,8,16,32,64];         %段内量化间隔表
+    codeDec=bin2dec(pcmcode);           %二进制编码字符串转换为十进制数值
+    ucode=bitand(codeDec,0b01111111);   %屏蔽极性位
+    k=bitshift(ucode,-4);               %右移4位，提取段落码
+    x0=code_table(k+1);                 %查表求段落起始电平
+    m=bitand(ucode,0b00001111);         %提取段内码
+    x1=double(m)*delta(k+1);            %求段内量化电平
+    dV=x0+x1+delta(k+1)/2;              %译码输出电平 
+    if codeDec<=128                     %处理极性
+        amp=-dV;
+    else 
+        amp=dV;
+    end
+end