基于Gardner定时同步算法的QPSK定时同步matlab仿真,包含仿真操作录像,代码中文注释

% QPSK 信号调制与解调 clear all; % 清除所有变量 close all; % 关闭所有图形窗口 clc; % 清除命令窗口 ps = 45e6; % 符号速率 rate = 8; % 过采样倍数 fs = rate * ps; % 采样率 fc = 120e6; % 中频 N = 2^16; % 符号长度 %% 调制 x = randint(1, N, [0 3]); % 随机生成0到3之间的整数作为输入符号 Ia = zeros(1, N); % 初始化I路幅度值 Qa = zeros(1, N); % 初始化Q路幅度值 qpsk = pskmod(x, 4, pi/4); % 进行QPSK信号调制 scatterplot(qpsk) % 绘制星座图 Id = zeros(1, N * rate); % 初始化I路调制信号 Qd = zeros(1, N * rate); % 初始化Q路调制信号 Id = upsample(real(qpsk), fs / ps); % I路调制信号上采样 Qd = upsample(imag(qpsk), fs / ps); % Q路调制信号上采样 n_T = [-2, 2]; % 时域成型滤波器长度范围 T = 1; % 样本间隔 shape_b = rcosfir(0.8, n_T, rate, T, 'sqrt'); % I路和Q路成型滤波器 rcosi = filter(shape_b, 1, Id); % I路过成型滤波器 rcosq = filter(shape_b, 1, Qd); % Q路过成型滤波器 de_data = rcosi(3:rate:end) + 1i * rcosq(3:rate:end); % 解调后数据点 temp = [qpsk; de_data]; % 组合调制前和解调后数据点，便于绘制星座图 t = 0:1/fs:(rate * N - 1) * 1/fs; % 时间序列 fi = cos(2 * pi * fc * t); % I路本地载波 fq = sin(2 * pi * fc * t); % Q路本地载波 qpsk_mod = fi .* rcosi + fq .* rcosq; % 混合调制信号 %% 解调部分 ff = 15; % 频偏 snr = 10; % 信噪比 qpsk_mod = awgn(qpsk_mod, snr, 'measured'); % 加入高斯噪声 demod_i = qpsk_mod .* cos(2 * pi * (fc + ff) * t); % I路解调 demod_q = qpsk_mod .* sin(2 * pi * (fc + ff) * t); % Q路解调 fdi = filter(shape_b, 1, demod_i); % I路过成型滤波器 fdq = filter(shape_b, 1, demod_q); % Q路过成型滤波器 base = fdi + 1j * fdq; % 解调后的基带信号 scatterplot(base, rate) % 绘制未定时同步信号的星座图 title('未定时同步信号星座图'); di = fdi(2:2:end); % 2倍抽取，抽取后每个符号4个采样点 dq = fdq(2:2:end); di = di./max(abs(di)); % 归一化处理 dq = dq./max(abs(dq)); % ****** Gardner 位同步算法 ********* c1 = 12 / 0.8 * 0.001; % 环路滤波器参数 c2 = 320 / 1 * 0.001 * 0.001; i = 4; k = 4; ms = 4; ns = length(di); n = [0.7, 0.7, 0.7, 0.7, zeros(1, ns - 4)]; n_temp = n; w = [0.5, 0.5, 0.5, 0.5, zeros(1, ns / 4 - 4)]; u = [0.6, 0.6, 0.6, 0.6, zeros(1, ns / 2 - 4)]; strobe = zeros(1, length(di)); yi = zeros(1, length(di)); yq = zeros(1, length(dq)); data_i = zeros(1, N); data_q = zeros(1, N); max_1 = 0; max_2 = 0; max_3 = 0; max_yi = 0; max_y4 = 0; while (i < ns) n_temp(i+1) = n(i) - w(ms); if n_temp(i+1) > 0 n(i+1) = n_temp(i+1); else n(i+1) = n_temp(i+1) + 1; % mod(n_temp(i+1), 1); % **** Fawwow 立方插值滤波器 ****** fi1 = 0.5 * di(i) - 0.5 * di(i - 1) - 0.5 * di(i - 2) + 0.5 * di(i - 3); fi2 = 1.5 * di(i - 1) - 0.5 * di(i) - 0.5 * di(i - 2) - 0.5 * di(i - 3); fi3 = di(i - 2); yi(k) = (fi1 * u(k) + fi2) * u(k) + fi3; fq1 = 0.5 * dq(i) - 0.5 * dq(i - 1) - 0.5 * dq(i - 2) + 0.5 * dq(i - 3); fq2 = 1.5 * dq(i - 1) - 0.5 * dq(i) - 0.5 * dq(i - 2) - 0.5 * dq(i - 3); fq3 = dq(i - 2); yq(k) = (fq1 * u(k) + fq2) * u(k) + fq3; strobe(k) = mod(k, 2); if strobe(k) == 0 %%% 定时误差检测算法，每个符号中需2点参与运算 data_i(k - 2) = yi(k); data_q(k - 2) = yq(k); err(ms) = yi(k - 1) * (yi(k) - yi(k - 2)) + yq(k - 1) * (yq(k) - yq(k - 2)); % 误差检测 w(ms + 1) = w(ms) + c1 * (err(ms) - err(ms - 1)) + c2 * err(ms); % 环路滤波 ms = ms + 1; end k = k + 1; u(k) = n(i) / w(ms); end i = i + 1; end figure; plot(err); data = data_i(2:2:end) + 1j * data_q(2:2:end); de_qpsk = pskdemod(data, 4, pi/4); % 解调后的QPSK信号 scatterplot(data(16:end)) % 绘制定时同步信号的星座图 title('定时同步信号星座图');