Airborne Radar Simulation, in the present context, is the real-time generation of radar displays and other radar outputs, such as data exchanges with the flight computer or other avionics subsystems, consistent with the actual radar and in response to the interaction with the operator, ownship, targets, and the environment.
The application is flight simulators for man-in-the-loop training of pilots and radar operators, and engineering research simulators for designing radars, avionics systems, and cockpits. Engineering research simulators are frequently used to aid integration and so may incorporate additional aircraft hardware. Otherwise, the requirements are similar to flight simulators. This paper addresses the Airborne Radar Simulator for flight simulator application. The focus is Air-To-Ground radar modes and thus the Digital Radar Landmass Simulator (DRLMS). Keywords: DRLMS, flight simulator, modeling, radar, remote sensing, simulator, training.
The radar contains a Radar Data Processor (RDP) and a Programmable Signal Processor (PSP). The RDP provides control of all the radar functions, tracking, motion compensation, and communications to the avionics computer. The PSP provides predetection and postdetection signal processing, display processing, range/azimuth compression, and other high-speed processing.
The exciter creates the modulated waveform that is amplified by the transmitter and radiated into space by the antenna. The A/D converter translates the receiver output from analog to digital for PSP processing. The gimbal servo unit is driven by the RDP and maintains antenna scan and stabilization.
Table 2 lists the three primary radar modes. The RBGM mode is a conventional radar mode. The only distinction is that with modern technology it is possible to match the radar resolution to the display resolution by variable pulse compression, and thus eliminate the collapsing losses present in earlier radars. The DBS mode is a scanning mode, providing constant azimuth resolution throughout the field of regard. It is generated by sequential batch processing of short, fixed-length FFTs performed at a variable PRF and combined (as adjacent segments) to give the continuous scan display. The SAR mode is a spotlight mode, providing constant cross-range resolution at any designated range/azimuth location. It is generated by a single, long FFT that is performed with motion compensation at a constant PRF. (In reality, several FFTs are used to provide adequate azimuth coverage and several looks, performed at different RF frequencies, are noncoherently combined to improve image quality.)
Both DBS and SAR modes require motion compensation. The aircraft motion is acquired from the inertial navigation system. Then the receiver Local Oscillator (LO) is offset by appropriate frequency to remove the instantaneous Line-Of-Sight doppler from the radar signal that is due to the aircraft.
Morales Romero Karelis
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