Delay doppler radar altimeter（DDA） is a new radar altimeter

which utilizes aperture synthesize to improve the measurement performance.Compared with conventional radar altimeter

DDA has the resolution along track being increased by 10 times

the transmitted peak power being reduced by 10dB

and the measurement precision of altitude being improved to 2cm.The higher measurement precision

the higher space resolution

and the lower transmitted power make DDA feasible to realize miniaturization.DDA represents a new generation of radar altimeter

and it is suitable to survey ocean

coastal zone

and polar ice.In this paper

the mechanism

the simulation of waveforms

and the precision analysis of DDA are discussed.