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The textbook I'm using to understand radar is explaining the 'pulse width dilemma'. It says that shorter pulse widths can resolve targets that are close together; however, because there is a limit to the amount of peak power the transmitter can achieve, this short pulse approach severely limits the maximum range from which targets can be reliably detected.

I don't understand why a short pulse limits the maximum range. Surely maximum range is determined by the amount of power to enable the pulse of energy to reach the target and have it reflected back again? Why should it matter whether the pulse is transmitted for x ms or y ms? At any given point in time, the same amount of energy will be hitting the target regardless of whether the pulse was for x ms vs y ms. It's not like there's a build-up of energy on the target before it reflects the signal back, it all happens instantaneously.

I know I'm missing something here. Hope someone can explain it.

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  • $\begingroup$ I don't know anything about radar, but for light sources it's pretty common that longer pulses contain more photons... you assume that the pulse energy is the same, but that is peak power times pulse width. $\endgroup$ Commented Sep 7, 2021 at 7:57

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This is probably more about the mathematics of signal processing than how the energy is reflected.

Besides the signal returning from the target, there is noise. Low power signals take a longer integration time to distinguish it from noise.

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  • $\begingroup$ I wondered if it was to do with the signal-to-noise ratio? $\endgroup$ Commented Sep 7, 2021 at 9:31

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