Hello all, I am trying to model a received laser signal, x(t), reflected off a moving target. I am currently trying to model for both frequency change due to Doppler shifting as well as a time-varying phase shift, θ(t), due to the continuous change in distance from the target. My current model is as follows: x(t) = cos(2∏(f+f0(t))t + θ(t)), where f0(t) is the Doppler effect at time t and θ(t)=(distance at time t)/wavelength. I do not assume constant velocity so the f0(t) may change over time. I am not sure if this physical model is correct. Any comments or suggestions are welcome. Thank you.