Define false alarm rate and how to control it.

• A. The total number of true targets detected per scan.
• B. The rate at which the radar transmits pulses.
• C. The number of tracks currently in the system.
• D. The frequency of non-target detections; controlled by threshold settings, gating, and clutter suppression.

Answer: (D)

The main idea here is what false alarm rate means. It’s the frequency with which the radar reports detections that aren’t real targets—returns caused by noise, clutter, or interference rather than actual objects. You control this rate by tuning the processing that decides what counts as a target: the detection threshold, the gating (which keeps detections to a plausible region in space, velocity, or time), and clutter suppression (methods that reduce reflections from static or predictable clutter, like a steady shoreline or sea clutter).

Why this option fits best: it directly defines false alarms as non-target detections and notes the practical ways to limit them—raising the detection threshold lowers false alarms but may miss faint targets, gating confines detections to expected areas, and clutter suppression reduces spurious returns from the environment.

The other ideas describe different radar concepts. It isn’t about the total number of true targets detected, nor about how fast the radar transmits pulses, nor about how many tracks are in the system. Those aspects relate to other performance metrics or system operation, not the definition and control of false alarms.