HIGH DOPPLER RATE HIGH ALTITUDE CAPABILITY COHERENT PULSED DOPPLER RADAR ALTIMETER

摘要

A pulse Doppler radar altimeter designed to resolve the ambiguous rangeproblem associated with the use of a pulse repetition interval, which is lessthan theaircraft altitude, includes a radar transmitter configured to transmit firstand secondseries of pulses where the first series has a pulse repetition intervalslightly differentfrom the pulse repetition interval of the second series. At a time when thefirst seriesis being transmitted, the receiver electronics including a range gate and atrackersearches for ground returns and positions the range gate in time coincidencewith thedetected ground return. Control then shifts so that the second series ofpulses istransmitted and a determination is made whether overlap of the range gate withtheground return from the second series corresponds to the same altitude as whenthefirst series was involved. If not, it is known that the detected range isambiguous andthe tracker continues repositioning the range gate (altitude) until anunambiguousrange determination is made.