function [s_T_narrow, A_narrow] = narrow_signal_model(t, betas_narrow)
    global f_c N_narrow N FIGURE N_wide numP f_s K_chirp T_r;

    tt = 0: 1/f_s: numP * T_r - 1/f_s;

    % 使用等效散射系数生成窄带情况信号模型
    s_T_narrow = zeros(1, N * numP);
    for j = 1: numP
        idx = ((j-1) * N + (1:N_narrow));
        tp = idx / f_s;
        s_T_narrow(1, idx) = exp(1j * 2 * pi * (f_c * tp + 0.5 * K_chirp * tp .^ 2));
    end

    % s_T_narrow = exp(1j .* 2 .* pi .* f_c .* t);
    s_R_narrows = zeros(N_narrow, N * numP);
    for i = 1: N_narrow
        p = i * (N_wide / N_narrow);
        s_R_narrows(i, :) = betas_narrow * [zeros(1, p), s_T_narrow(1: end-p)];
    end
    
    A_narrow = s_R_narrows';
    if FIGURE
        subplot(2, 1, 1); plot(tt, real(s_T_narrow));
        subplot(2, 1, 2); plot(tt, real(s_R_narrows(1, :)));
    end