说明：  去斜率（strech）参考信号与回波信号混频后得到中频输出信号S(t)=Aexp(j*2*pi*f0*t+phase) 其中f0与回波延时的关系为： f0=k*delay_t K为线性调频斜率，delay_t为回波延时 将s(t)采样，FFT变换即可得到目标距离与频谱的关系。 Strech 信号测距 输入混频后的中频信号（图一），经采样及FFT变换得到频谱（图二） 再根据频谱与距离的关系式R=Tcf/2B显示出距离(图三)
(Go slope (strech) obtained after the reference signal and the echo signal mixer IF output signal S (t) = Aexp (j* 2* pi* f0* t+phase) f0 and echo delay relationship: f0 = k* delay_t K chirp slope, delay_t the echo delay sampling s (t), the FFT transform to the target distance spectrum of relations. Strech signal ranging input mixer IF signal (Figure 1), sampling and FFT transform spectrum (Figure 2) according the the spectrum distance relationship R = Tcf/2B shows the distance (Figure 3))