High Doppler rate, high altitude capability coherent pulse Doppler radar altimeter

An aircraft pulse Doppler radar altimeter for providing ambiguous range rejection, comprising:

• (a) means for separately transmitting, when enabled, a first and a second sequence of pulses of a first and a second pulse repetition interval, respectively;
• (b) timing and control means for periodically enabling said means for transmitting said first and second sequence of pulses on a time-shared basis;
• (c) receiver means including range gate means for receiving ground return signals corresponding to said first and second sequence of pulses;
• (d) means, including said timing and control means, coupled to said range gate means for continuously adjusting the time following the transmission of the pulses in said first sequence of pulses at which said range gate is enabled until said receiver means detects a ground return signal overlapped by said range gate;
• (e) means responsive to the detection of an overlap of ground return resulting from said first sequence of pulses with said range gate for causing said timing and control means to initiate transmission of said second sequence of pulses and for determining whether a ground return corresponding to said second sequence of pulses is overlapped by the then position of said range gate;
• and
• (f) means for reinitiating said means coupled to said range gate means when said detection responsive means determines the absence of overlap between said ground return corresponding to said second sequence of pulses and said then position of said range gate means.