Pulse Duration (PD), Pulse Repetition Period (PRP) and Duty Factor (DF)

  • Thread starter markieboy
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  • #1
markieboy
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Homework Statement:
Pulse duration (PD) is the time from the start to the end of a pulse.
Pulse repetition period (PRP) is the time from the start of one pulse to the start of the next pulse.
Duty factor (DF) is the percentage of that time that sound is created by the transducer.

The number of cycles in each pulse increases:
1) The PD increases/decreases/stays the same.
2) The PRP increases/decreases/stays the same.
3) The DF increases/decreases/stays the same.

The number of pulses completed each second increases:
4) The PD increases/decreases/stays the same.
5) The PRP increases/decreases/stays the same.
6) The DF increases/decreases/stays the same.

The number of cycles completed each second increases:
7) The PD increases/decreases/stays the same.
8) The PRP increases/decreases/stays the same.
9) The DF increases/decreases/stays the same.
10) The number of cycles in each pulse increases/decreases/stays the same.
Relevant Equations:
PD = (# of cycles)(period)
PRP = time/pulses
DF = (PD/PRP)*100
I attempted this assignment, and scored a 5/10. The solutions are not given until a later date. I need to understand this material before I progress to the next section. The following are my attempts at the solution.

The number of cycles in each pulse increases:
The PD is determined by the number of cycles and the period. If the number of cycles increases, the PD increases. One component of the PRP is the PD. So, the PRP increases. If both PD and PRP increases, the ratio of the DF stays the same.
1) The PD increases.
2) The PRP increases.
3) The DF stays the same.

The number of pulses completed each second increases:
This is the definition of PRF, which is the reciprocal of PRP. If PRF increases, PRP decreases. PD is not affected. It stays the same. Since only PRP decreases, DF increases.
4) The PD stays the same.
5) The PRP decreases.
6) The DF increases.

The number of cycles completed each second increases:
This is the definition of frequency, which is the reciprocal of period. PD is affected by the period. Frequency increases, period decreases. Therefore, PD will decrease. PRP will decrease. Since both decrease, the DF will remain the same. The number of cycles in each pulse stays the same.
7) The PD decreases.
8) The PRP decreases.
9) The DF stays the same.
10) The number of cycles in each pulse stays the same.

I am unsure what questions I got wrong. If someone can point out my errors, I would appreciate that very much.

Thank you!
 

Answers and Replies

  • #2
BvU
Science Advisor
Homework Helper
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Hi @markieboy,
:welcome: !​

Could be my shortcoming, but in this story I miss something: am I supposed to assume a pulse consists of a number of cycles of a sound signal with a fixed frequency ?

That would explain the PD = (# of cycles)(period) relevant equation.

And then I agree with your 1) answer.
But why would that mean the PRP increases as well ? (your 2) answer )
Is there something in the full problem statement that gives you that impression ? Or did you type the full problem statement exactly as it was given to you ?
I would expect the signal generator to give a next pulse after a fixed time from the start of the previous pulse (not after the termination).
So I also disagree with your 3) answer

I agree with 6) 7) 8)

PD is affected by the period
Why ? Number of cycles/second = frequency. The frequency increases but the PD can stay the same ?
That way PD, PRP and DF all three stay the same

Perhaps it's a good idea to make sketches of the waveforms ?

##\ ##
 

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