The 'M of N' function in PSR serves primarily to eliminate which type of targets?

The 'M of N' function in PSR serves primarily to eliminate which type of targets?

• A. Second-time-around targets
• B. First-time targets
• C. Moving targets only
• D. Ground clutter

Answer: (A)

The main idea being tested is how the M of N logic works to confirm detections across multiple scans. M of N requires a target to be observed in at least M of N consecutive radar sweeps to be accepted as valid. This makes the system filter out transient or spurious echoes that don’t persist across scans. Why this points to eliminating second-time-around targets: false echoes often appear intermittently or only on a secondary pass due to processing artifacts, multipath, or clutter. They don’t reliably show up in the required number of scans, so they fail the M of N criterion and are discarded. Real targets, including moving aircraft, tend to be seen in multiple scans, so they survive the test. In short, the M of N filter emphasizes persistence over time, which is why it’s most effective at removing second-time-around targets rather than real targets or clutter that would either persist differently or not be the primary issue under this rule.

The main idea being tested is how the M of N logic works to confirm detections across multiple scans. M of N requires a target to be observed in at least M of N consecutive radar sweeps to be accepted as valid. This makes the system filter out transient or spurious echoes that don’t persist across scans.

Why this points to eliminating second-time-around targets: false echoes often appear intermittently or only on a secondary pass due to processing artifacts, multipath, or clutter. They don’t reliably show up in the required number of scans, so they fail the M of N criterion and are discarded. Real targets, including moving aircraft, tend to be seen in multiple scans, so they survive the test.

In short, the M of N filter emphasizes persistence over time, which is why it’s most effective at removing second-time-around targets rather than real targets or clutter that would either persist differently or not be the primary issue under this rule.