数字信号升采样降采样matlab例程

在MATLAB中，数字信号处理通常涉及到采样和量化等操作。升采样和降采样是改变信号样本率的基本步骤。以下是简单的例子：

**升采样 (Upsampling)：**

function upsampled_signal = up_sampling(x, ratio)
    % 输入：原始信号x，升采样的比率ratio
    N = length(x);
    upsampled_ratio = ratio;
    upsampled_length = N * upsampled_ratio;
    
    % 创建新的时间轴
    t = linspace(0, 1/(Fs), N); % 假设原始信号的频率 Fs=1 (单位：Hz)
    new_t = linspace(0, 1/(Fs*upsampled_ratio), upsampled_length);

    % 使用线性插值进行升采样
    upsampled_signal = interp1(t, x, new_t, 'linear');
end

**降采样 (Downsampling)：**

function downsampled_signal = down_sampling(x, ratio, mode)
    % 输入：原始信号x，降采样的比率ratio，滤波模式mode可以选择'average'或'nearest'
    N = length(x);
    downsampled_ratio = ratio;
    if mod(N, downsampled_ratio) == 0
        downsampled_length = floor(N/downsampled_ratio);
    else
        error('Downsampling ratio must evenly divide the signal length.');
    end

    % 选择降采样方式（平均法或最近邻法）
    if strcmp(mode, 'average')
        downsampler = @(y) mean(y(round(linspace(1, N, downsampled_length))));
    elseif strcmp(mode, 'nearest')
        downsampler = @(y) y(round(downsampled_length*(linspace(1, 1, N)+0.5)-0.5));
    else
        error('Invalid downsampling method.');
    end
    
    downsampled_signal = downsampler(x);
end