Why modulation?
Because useful signals tend to have low frequencies, while signals suitable for antenna transmission tend to have relatively high frequencies. So adjustments are required. Simply put, it is to modulate a low frequency signal to a high frequency.
modulation simulation
Simple simulation with matlab, a low-frequency signal and a high-frequency signal are mixed to realize the modulation process.
%% 信号包络，调频的调制过程展示
% 2022.5.26
T = 1; % 总时间
fs = 1000; % 采样率
dt = 1/fs; % 采样间隔
t = 0:dt:1; % 时间刻度向量
f1 = 2; %基带信号频率
f2 = 50; % 载频
x = cos(2*pi*f1*t); % 基带信号
x2 = cos(2*pi*f2*t); % 载频
x3 = x.*x2; % 调制
plot(t,x,'--',t,x3) % 绘图
legend('包络','调制信号')
The plot is as follows:
