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一、简介

脉冲编码调制（PCM）是一种将连续变化的模拟信号转换为离散的数字信号并通过信道传输的技术。PCM的核心过程包括抽样、量化和编码三个步骤。抽样是将连续的模拟信号变为时间离散的数字信号，确保在不失真情况下恢复原信号。抽样速率通常由抽样定理确定，电话系统中常用8KHz的抽样率。

量化则是将抽样后的瞬时值的幅度离散化，采用固定电平将属各个定点的值映射到相应的电平区间。量化后的信号仅包含有限个数值，体现了数字信号特性。量化过程实际上与编码过程紧密结合，称为模数转换（A/D转换），将模拟信号转为二进制数字码。

电话系统中，常用抽样率为8KHz，每个抽样值对应8位二进制码，共256个量化级别。因此，每话路PCM编码后的标准数码率为64kb/s。为了提高信噪比，特别是在处理非均匀信源时，非均匀量化方法被普遍采用。该方法通过动态调整量化间隔，使小信号幅度的量化精度更高，大信号则相反。这一技术特别适用于像语音信号这样的小信源，能够显著提升信噪比和音质。

二、源代码

function varargout = PCM(varargin)    % PCM M-file for PCM.fig    % PCM was designed to demonstrate how PCM works    % Users can choose between three sampling methods    % After sampling, users can quantize the signal using two rules and one algorithm    % The "Squeezing and Stretching" option shows the best G(x) that minimizes MSE    % Users can adjust the number of bits and the number of iterations    % The picture shows the quantized signal, the first iteration of quantization, and the quantizer output    % Pressing the Bit Stream button displays the PCM output    % Every change requires pressing the related button    % Details in the comments    % Last modified by GUIDE v2.5 14-Mar-2007 12:32:35    gui_Singleton = 1;    gui_State = struct('gui_Name', mfilename, ...        'gui_Singleton', gui_Singleton, ...        'gui_OpeningFcn', @PCM_OpeningFcn, ...        'gui_OutputFcn', @PCM_OutputFcn, ...        'gui LayoutFcn', [], ...        'gui_Callback', []);ifdef nargin && ischar(varargin{1})    gui_State.gui_Callback = str2func(varargin{1});endifnargout = [varargout{1:nargout}] = gui_mainfcn(gui State, varargin{:});else    gui mainfcn(gui State, varargin{:});endfunction PCM_OpeningFcn(hObject, eventdata, handles, varargin)    % Opens PCM GUI    handles.output = hObject;    guidata(hObject, handles);    uiwait(handles.figure1);endfunction varargout = PCM_OutputFcn(hObject, eventdata, handles)    % Returns output data    varargout{1} = handles.output;end% ....Below is the callback functions for buttons and radiobuttons

三、运行结果

四、备注

完整代码或仿真的详细咨询：202** **.REMOVE

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