What eliminates second-time-around targets in the Primary Surveillance Radar (PSR)?

What eliminates second-time-around targets in the Primary Surveillance Radar (PSR)?

• A. Staggering the coherent processing interval (CPI) and performing an M of N function
• B. Increasing PRF
• C. Switching to a different frequency
• D. Reducing transmitter power

Answer: (A)

Second-time-around echoes are false targets that appear when the return from a target arrives in a later processing cycle as if it were a new target in the current cycle. In PSR, coherent processing sums returns over a coherent processing interval, so a second trip can be reinforced if not managed. Staggering the CPI changes which pulses are combined in each processing interval so that a second-trip echo does not align coherently across CPIs. The M of N function then acts as a gate: a real target must appear in a minimum number of the staggered CPIs to be accepted. Since second-time-around echoes typically don’t persist across the staggered CPIs, they fail the acceptance criteria and are rejected. This processing approach specifically targets and removes second-trip artifacts without needing to alter transmitter power or frequency.

Second-time-around echoes are false targets that appear when the return from a target arrives in a later processing cycle as if it were a new target in the current cycle. In PSR, coherent processing sums returns over a coherent processing interval, so a second trip can be reinforced if not managed. Staggering the CPI changes which pulses are combined in each processing interval so that a second-trip echo does not align coherently across CPIs. The M of N function then acts as a gate: a real target must appear in a minimum number of the staggered CPIs to be accepted. Since second-time-around echoes typically don’t persist across the staggered CPIs, they fail the acceptance criteria and are rejected. This processing approach specifically targets and removes second-trip artifacts without needing to alter transmitter power or frequency.