Digital generation of high time-bandwidth product linear FM waveforms for radar altimeters

A method is described and demonstrated of generating linear FM waveforms of very high time bandwidth product (in excess of 105) with range sidelobe levels more than adequate for future generation radar altimeters. The technique is extremely flexible, and the pulse length and bandwidth are easily varied by changing the parameters of the digital circuitry. An analysis is developed to relate the level of phase and amplitude errors to the permissible range sidelobe level, showing that considerably greater phase errors can be tolerated than for conventional pulse compression radars, and the validity of this analysis is confirmed by experiment.