Aircraft radar altimeter with multiple target tracking capability

Claim 1

A radar altimeter multiple target tracking system comprising: (a) means for repeatedly transmitting pulses of electromagnetic energy at a predetermined power level from an aircraft towards the earth's surface; (b) means for receiving return pulse signals from said surface and from objects extending upward from said surface; (c) closed-loop tracking means including a range gate coupled to said receiving means for determining from the time interval between transmitted pulses and the position of said range gate when overlapping the leading edge of the corresponding return pulse signals from said earth's surface the altitude of said aircraft relative to said earth's surface; (d) means for periodically interrupting said closed-loop tracking means and storing said altitude and power level information in a memory while searching for returns from said objects, if any; (e) means for resuming operation of said closed-loop tracking means for tracking said return signal from said object and determining from the time interval between transmitted pulses and the position of said range gate when overlapping the leading edge of the corresponding return pulse signals from said object the altitude of said aircraft relative to said object; (f) means for storing the altitude and power level information relative to said object in said memory; and (g) means for alternately reading out the contents of said memory means to said tracking means whereby tracking of said return pulse signals from the earth's surface and said object are interleaved and resumed from an altitude and at a power level value stored in said memory.