Requirements of a coherent laser pulse-Doppler radar

The use of coherent detection can theoretically allow optical radar systems employing laser transmitters to achieve considerably improved receiver sensitivity, particularly in conditions of high background radiation. However, there are many practical factors that can limit sensitivity in coherent optical detection, which are described. It is shown that to achieve an efficient coherent optical radar, one would generally like a pulse width less than 10 µsec and a spectral line width less than 10 Mc.