Abstract: In order to measure low-altitude flight targets,an 8 mm CW radar with pseudo-noise code modulation is developed.Its signal ambiguity function approaches the impulse function in two-dimensional(τ,ωd) plane.It is beneficial to reduce the sea clutter interference and improve distinguishability to the target.The echo signal is received by an radar receiver with maximum likelihood estimation technology.The estimation of Doppler frequency and code delay are carried out in the approximately maximum likelihood manner of quasi-open loops.The high dynamic targets must be tracked by the method.Simulations and demonstration tests show that the propoed radar can stably track high dynamic low-altitude flight targets in low S/R on the sea,even if the receiving level undulates in 20 dB.