Or you try all the possible solutions all at once in parallel in a big FPGA and you have instant synch (at least in the time it takes to recognize you have it)
May be impractical for very long, complex sequences... Didier KO4BB Sent from my Verizon Wireless BlackBerry -----Original Message----- From: jimlux <[email protected]> Sender: [email protected] Date: Wed, 16 Feb 2011 21:26:01 To: <[email protected]> Reply-To: Discussion of precise time and frequency measurement <[email protected]> Subject: Re: [time-nuts] PN sequence generation using GPS On 2/16/11 5:04 PM, Joe Leikhim wrote: > Thanks Bob; > > Does this mean that the 10 MHz clock needs to be somehow divided to an > integer evenly divisible by 127 seconds? > > Also 8192 seems to be unfeasible as it would take 2.2 hours to > initialize sync. > No.. your 1pps/sync loads the register with all ones... that's what the sync is. If you want to synchronize without "help", what you do is slide the receiver steadily by the transmitter, slipping one chip at a time (or offsetting the frequency slightly). The challenge is that you need to be "close enough" as you slide by for "long enough" to recognize that you've got sync. Say you've got a 1023 long code (a 10 bit generator) running at 1 MHz. Say it takes 1 millisecond to tell if you are in sync. You can try all 1023 possible relative phases in 1 second, roughly, and the average time will be a half second. You can do this "try all phases" by running one clock 1ppm slow, relative to the other, or you can run them at the same speed, and drop a pulse every code period. Depends on if you have a digital or analog implementation.. For a digital implementation, it's often convenient to detect when the generator register is all ones, which occurs only once a code period. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
