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Design >> RF Design >> duty ratio
https://designers-guide.org/forum/YaBB.pl?num=1267727859

Message started by manikandan on Mar 4^th, 2010, 10:37am

Title: duty ratio
Post by manikandan on Mar 4^th, 2010, 10:37am

hi,

i have a pulse that has literally 100% duty ratio..i need a duty ratio of 50..how can i do it..

i have to feed this pulse to input of phase detector..so need 50 duty cycle..

Title: Re: duty ratio
Post by rfcooltools.com on Mar 5^th, 2010, 10:51pm

Phase detectors are usually d-flipflops with a reset. therefore your pulse needs only to be long enough to ensure flip-flop operates (setup hold) correctly. 50% duty cycle is not important since almost all phase detectors us one edge of the clock. If this pulse train you have is from a frequency doubler or needs to go into one then that is another issue.

Title: Re: duty ratio
Post by ultimate on Mar 6^th, 2010, 12:38am

hi..

my pulse goes from frequency divider..so duty ratio is important..any idea?

Title: Re: duty ratio
Post by oermens on Mar 6^th, 2010, 10:48am

maybe some clues from here:

http://www.designers-guide.org/Forum/YaBB.pl?num=1267087013
http://www.designers-guide.org/Forum/YaBB.pl?num=1244030892

Title: Re: duty ratio
Post by loose-electron on Mar 7^th, 2010, 12:20pm

PLL and frequency multiplication is the classic way of doing this.

If you have either a high frequency oscillator or can create one there are some digital counter tricks to get what you want:

Count the period of the wave, divide by 2 and use that to create a sort of 50% cycle wave.

Analog techniques -- LPF the signal to the fundamental sinusoid. The amplify back to a square wve.

some ideas

Title: Re: duty ratio
Post by tkhan on Mar 7^th, 2010, 3:46pm

can you use master-slave dff to create 4 phases of 50% duty cycle @ f/2, then XOR 2 phases which are 90deg apart to get 50% duty cycle @ f?