f0=1500;
Bw=1e3;
fl=f0-Bw/2;fh=f0+Bw/2;
fs=30e3;
A=0.5;
T=10e-3;
k=Bw./T;
t=0:1./fs:T;
sig_LFM1=A*chirp(t,fl,T,fh);
% sig_LFM2=A*cos(2*pi*fl.*t+pi.*k.*t.^2);
figure
plot(t,sig_LFM1)
% hold on
% plot(t,sig_LFM2,'r')
xlabel('时间/秒')
ylabel('幅度/伏')
title('LFM信号')
axis([0 T -1 1])
grid on