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The multibeam monopulse radar for Airborne Based Sense and Avoid (ABSAA) system concept is the next step in
the development of passive monopulse direction finder proposed by Stephen E. Lipsky in the 80s. In the proposed
system the multibeam monopulse radar with an array of directional antennas is positioned on a small aircaraft or
Unmanned Aircraft System (UAS). Radar signals are simultaneously transmitted and received by multiple angle
shifted directional antennas with overlapping antenna patterns and the entire sky, 360° for both horizontal and vertical
coverage. Digitizing of amplitude and phase of signals in separate directional antennas relative to reference signals
provides high-accuracy high-resolution range and azimuth measurement and allows to record real time amplitude
and phase of reflected from non-cooperative aircraft signals. High resolution range and azimuth measurement
provides minimal tracking errors in both position and velocity of non-cooperative aircraft and determined by
sampling frequency of the digitizer. High speed sampling with high-accuracy processor clock provides high
resolution phase/time domain measurement even for directional antennas with wide Field of View (FOV). Fourier
transform (frequency domain processing) of received radar signals provides signatures and dramatically increases
probability of detection for non-cooperative aircraft. Steering of transmitting power and integration, correlation
period of received reflected signals for separate antennas (directions) allows dramatically decreased ground clutter
for low altitude flights. An open architecture, modular construction allows the combination of a radar sensor with
Automatic Dependent Surveillance – Broadcast (ADS-B), electro-optic, acoustic sensors.
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