19 / 20
What is the pulse power of a radar pulse string?
• A
average pulse power multiplied by pulse width
• B
peak pulse power
• C
power measured over the period of the pulse width
• D
the continuous power

Refer to figure.
Power is defined as the rate of energy transfer per second. The higher power an antenna is, the stronger its signals, and therefore the further the signals will be able to travel before being fully absorbed by the atmosphere.

A pulse radar fires a pulse for a short time, then waits a much longer time to look for any reflected signals from any potential objects in its path. We do not want to measure the radar’s power when it is waiting, as there is no power output during that time.

This is why we measure the energy emitted over the period of the pulse width only, and then we can average that power over the pulse width to find the power of the radar pulse.

The big problem with this question is that there are two answers which are correct. As the radar fires a pulse of near enough continuous energy (for that short time), the peak power can be referred to as the pulse power, as they are usually the same value. This is the same as "power measured over the period of the pulse width", as a radar pulse should produce a continuous amount of power during the pulse width.

The big thing to remember is that the average power output of the radar is much less than the pulse power (peak power), as this value has then been averaged out over the whole pulse cycle, which is mostly filled with no power output (see annex above).

Note: There has been recent feedback from two authorities that the correct answer is "peak pulse power", but if the option "power measured over the period of the pulse width" also appears, then an appeal (and certainly a comment - if possible) could be made, as we believe this is an equally correct answer. Any exam feedback on this would also be useful, thank you.

Your Notes (not visible to others)

This question has appeared on the real examination, you can find the related countries below.