Final answer:
Increasing the pulse repetition frequency causes the duty factor to increase, provided all other factors remain the same, as the system is active more frequently. This is based on the definition of duty factor as the ratio of the active time to the total time for a pulse wave.
Step-by-step explanation:
When the pulse repetition frequency (PRF) increases, the duty factor also increases. The duty factor is defined as the ratio of the pulse duration to the period of the waveform, or, in other words, the fraction of time that the system is active versus the whole time period. As the PRF increases, pulses occur more frequently, which means the system is active for a greater portion of time, resulting in an increased duty factor, considering all other factors remain unchanged.
However, if the pulse duration were to remain the same while the frequency increases, the interval between pulses would decrease, making the system active more often over a set period of time. This leads to an increase in the duty cycle. Therefore, if all other factors remain unchanged, when pulse repetition frequency increases, the duty factor increases.