GMSK的调制解调matlab代码

以下是GMSK的调制和解调的MATLAB代码示例：

调制代码：

% GMSK Modulation
% Input: Bit stream, BT product
% Output: Modulated signal

function [s, t] = gmsk_modulation(bits, BT)
    % Bit stream to symbols
    M = 2; % QPSK modulation
    symbols = bi2de(reshape(bits, M, [])', 'left-msb');
    symbols = pskmod(symbols, M, pi/M);
    
    % GMSK modulation
    fs = 100; % Sampling frequency
    Ts = 1/fs; % Sampling interval
    Tb = 1; % Bit period
    Tb_s = round(Tb/Ts); % Number of samples per bit
    fc = BT/Tb; % Carrier frequency
    kf = 1/(2*pi*fc*Tb); % Modulation index
    phi = 0; % Initial phase
    s = zeros(1, Tb_s*length(symbols));
    for i = 1:length(symbols)
        for j = 1:Tb_s
            phi = phi + 2*pi*kf*(symbols(i)-1/2)*sin(2*pi*fc*j*Ts+phi);
            s((i-1)*Tb_s+j) = sin(phi);
        end
    end
    
    % Time axis
    t = (0:length(s)-1)*Ts;
end

解调代码：

% GMSK Demodulation
% Input: Modulated signal, BT product
% Output: Bit stream

function bits = gmsk_demodulation(s, BT)
    % GMSK demodulation
    fs = 100; % Sampling frequency
    Ts = 1/fs; % Sampling interval
    Tb = 1; % Bit period
    Tb_s = round(Tb/Ts); % Number of samples per bit
    fc = BT/Tb; % Carrier frequency
    kf = 1/(2*pi*fc*Tb); % Modulation index
    phi = 0; % Initial phase
    bits = zeros(1, length(s)/Tb_s);
    for i = 1:length(bits)
        sample = s((i-1)*Tb_s+1:i*Tb_s);
        phi_diff = diff(unwrap(angle(sample)));
        bits(i) = sum(phi_diff > 0)/(2*pi);
    end
    
    % Symbols to bit stream
    M = 2; % QPSK modulation
    symbols = pskdemod(de2bi(bits, M, 'left-msb'), M, pi/M);
    bits = reshape(de2bi(symbols, M, 'left-msb')', 1, []);
end

需要注意的是，这里使用了QPSK调制，因此输入的比特流应该是2的倍数。另外，BT product可以根据具体的系统要求进行调整。