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Mini-automatic radar plotting aid (or MARPA) is a maritime radar feature for target tracking and collision avoidance. Targets must be manually selected, but are then tracked automatically, including range, bearing, target speed, target direction (course), CPA (closest point of approach), and TCPA (time of closest point of approach), safe or dangerous indication, and proximity alarm.
The L band (1 to 2 GHz) electronically scanned AEW and surveillance radar is located on a dorsal fin on top of the fuselage, dubbed the "top hat", and is designed for minimal aerodynamic effect. The radar is capable of simultaneous air and sea search, fighter control and area search, with a maximum range of over 600 km (look-up mode).
To scan a portion of the sky, a non-PESA radar antenna must be physically moved to point in different directions. In contrast, the beam of a PESA radar can rapidly be changed to point in a different direction, simply by electrically adjusting the phase differences between different elements of the passive electronically scanned array (PESA).
However, in most fielded systems, unwanted clutter and interference sources mean that the noise level changes both spatially and temporally. In this case, a changing threshold can be used, where the threshold level is raised and lowered to maintain a constant probability of false alarm. This is known as constant false alarm rate (CFAR) detection.
A typical shipboard ARPA/radar system. A marine radar with automatic radar plotting aid (ARPA) capability can create tracks using radar contacts. [1] [2] The system can calculate the tracked object's course, speed and closest point of approach [3] (CPA), thereby knowing if there is a danger of collision with the other ship or landmass.
In order to implement this output signal for a practical triggering of a load such as a relay or a data logger, or an alarm, the differential signal is rectified using a bridge rectifier and fed to a transistorized relay driver circuit. The contacts of this relay close and open in response to the signals from the PIR, activating the attached ...
A buzzer or beeper is an audio signaling device, [1] which may be mechanical, electromechanical, or piezoelectric (piezo for short). Typical uses of buzzers and beepers include alarm devices , timers , train and confirmation of user input such as a mouse click or keystroke.
Common circuit diagram symbols (US ANSI symbols) An electronic symbol is a pictogram used to represent various electrical and electronic devices or functions, such as wires, batteries, resistors, and transistors, in a schematic diagram of an electrical or electronic circuit. These symbols are largely standardized internationally today, but may ...