Here's a paper on phase noise in Actel's devices. As a note Actel's "antifuse" technology is a bit different than than other companies in the CPLD/ FPGA market. They're OTP, rad hard, and very secure. I've seen them used as a system security measure between an external modem and an internal CPLD/ FPGA. I did some design work a few years ago rolling PLLs into CPLDs for Stratum 3 applications and the results were very interesting. I was using the brand X devices tested in the paper below and confirmed some of the results.
http://www.actel.com/documents/JitterWP.pdf Sean On Feb 2, 2011, at 2:17 PM, time-nuts-requ...@febo.com wrote: > Send time-nuts mailing list submissions to > time-nuts@febo.com > > To subscribe or unsubscribe via the World Wide Web, visit > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > or, via email, send a message with subject or body 'help' to > time-nuts-requ...@febo.com > > You can reach the person managing the list at > time-nuts-ow...@febo.com > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of time-nuts digest..." > > > Today's Topics: > > 1. Re: From GPS World - Lightsquared has been given the goahead > (Chris Albertson) > 2. Re: Lightsquared and a little math (Bob Camp) > 3. Re: GPS receiver jamming (John Green) > 4. Re: Lightsquared and a little math (Stanley Reynolds) > 5. Re: Lightsquared and a little math (Chris Albertson) > 6. Re: Frequency multiplication (Hal Murray) > 7. Re: Lightsquared and the FCC (Pete Lancashire) > 8. Re: Frequency multiplication (David Armstrong) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Wed, 2 Feb 2011 10:20:21 -0800 > From: Chris Albertson <albertson.ch...@gmail.com> > Subject: Re: [time-nuts] From GPS World - Lightsquared has been given > the goahead > To: Discussion of precise time and frequency measurement > <time-nuts@febo.com> > Message-ID: > <AANLkTimK_bzjZS03n7v2PJPPNmD_yfaGRRd_y=2gm...@mail.gmail.com> > Content-Type: text/plain; charset=ISO-8859-1 > > On Wed, Feb 2, 2011 at 10:02 AM, paul swed <paulsw...@gmail.com> wrote: >> True enough there will be three systems heck many channels also. >> But that reality actually means my magical HP 3801 may not work or could >> become unreliable at best. >> So how do we hack those new receivers for time-nuts purposes for $29? > > For $29? Maybe a home brew antenna with better patterns and maybe > even nulls aimed at nearby transmitters. It is surprisingly easy to > build a helix antenna. > > A notch filter can also be constructed to notch out the jammer if it > is out of band. A "twin T" design might be effective and low cost > > Microwave is line of site so maybe just a meter plate that blocks view > of the transmitter. > > The solution for a fixed timing receiver will be much easier than for > a mobile GPS receiver. > -- > ===== > Chris Albertson > Redondo Beach, California > > > > ------------------------------ > > Message: 2 > Date: Wed, 2 Feb 2011 13:23:55 -0500 > From: "Bob Camp" <li...@rtty.us> > Subject: Re: [time-nuts] Lightsquared and a little math > To: "'Discussion of precise time and frequency measurement'" > <time-nuts@febo.com> > Message-ID: <60b8a8a8e6584d2cb3affad4f5bf9...@vectron.com> > Content-Type: text/plain; charset="us-ascii" > > Hi > > There's no decision that they take that they can't reverse. That goes double > for something like this that was done pretty quickly. > > My guess is that they have a limited rather than a full approval at this > point. From the article "proceed with ancillary terrestrial component > operations" does not sound like a full license. > > If you do a little Google work on the topic, there are a lot of different > services and outfits impacted by this (not just GPS). None of them are happy > and all of them are likely on the phone to their favorite legislator and / > or lawyers. > > Bob > > -----Original Message----- > From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On > Behalf Of Pete Lancashire > Sent: Wednesday, February 02, 2011 1:13 PM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] Lightsquared and a little math > > Go back to my orig post the FCC has given the go ahead .. to late ? > > On Wed, Feb 2, 2011 at 9:57 AM, Bob Camp <li...@rtty.us> wrote: >> Hi >> >> Let's see, a 13 mile circle is pi r squared = ~ 530 square miles. >> 40,000 times 530 is ~ 21 million square miles. >> Wikipedia tells me that the area of the US is 3.79 million square miles. >> >> On that basis, there's not going to be anywhere in the US that you *can* > get >> GPS to fly a plane. Jamming detected = could be a problem = you can't > trust >> it. >> >> I suspect that there indeed will be remote parts of Alaska or the like > that >> you will indeed still have un-jammed coverage in a plane. >> >> Now for the "best case": >> >> 5.6 miles loss of fix = just under 100 square miles. That's 3.94 million >> square miles of jamming. That's still greater than the area of the US. I'm >> sure we'll have some left over to jam Canada and Mexico as well. Again, >> there will be patches where you can get a fix, but they will be the >> exception rather than the rule. >> >> File an IFR flight plan based on any of this - no way. Insure an airline >> that does that - no way. Run an airline based on "VFR only" not going to >> happen. Is everything GPS based - no, but there's a lot of the country > where >> it is. >> >> Not at all clear how you will keep aviation going under those conditions >> unless Lightsquared replaces all their gear with *type accepted* >> replacements. Where do I sign up for my free gps? >> >> Let's suppose they have big pockets and do all that. >> >> At the consumer level, you have 128 thousand square miles with urban > canyon >> issues. Good bet that's every place with an urban canyon in the country. >> Essentially cross off GPS in every large city. >> >> Out here in the sticks, things are a little better. Only a bit over 17 >> thousand square miles lost. Except ... do you have any hills or mountains >> near you? Back to the paragraph above if you live anywhere other than >> western Kansas. >> >> Why are they setting this up - to get internet to people. Where are the >> transmitters going - where people live. The consumer numbers may not sound >> as bad, but there's a lot of country that is pretty empty. Look at any > cell >> coverage map to get a good idea how much. You still nuke a lot of voters >> with "only" 17 thousand square miles. Not to mention fire, police, EMS, > and >> the DHL guy. >> >> Then you have the federal law about 911 tracking on cell phones. How does >> that work - GPS. Under what conditions - worse than an urban canyon (no > sky >> at all). You *at least* have the urban canyon area to deal with and likely >> worse. Any bet your cell phone GPS is as RF rugged as the one in your car? >> I'm not taking that bet. Bop up the coverage area a bit more. >> >> So average urban canyon with airborne and what do you get - just a bit > over >> a half million square miles. My guess is that's the whole area of the >> country that has a population dimensioned in multiple people per square >> mile. >> >> So we have: >> >> 1) Multiple Airplanes running into mountains >> 2) Many houses burning to the ground >> 3) Lots of 911 calls getting miss directed and people dying as a result >> 4) Joe six pack getting lost on the way to the beer store >> >> All could be what nukes this. I'm betting on number 4 ... >> >> Bob >> >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > > > > ------------------------------ > > Message: 3 > Date: Wed, 2 Feb 2011 12:28:11 -0600 > From: John Green <wpxs...@gmail.com> > Subject: Re: [time-nuts] GPS receiver jamming > To: time-nuts@febo.com > Message-ID: > <aanlktim299pgx6vequqh_t4tc7qkcag-rktfrfzjz...@mail.gmail.com> > Content-Type: text/plain; charset=ISO-8859-1 > > The timing grade receiver I have, a Z3801 absolutely lays down at the > least possible amount of on frequency signal. My automotive grade > Garmin is immune to even high levels. It may be that the slightest > degradation is unacceptable to the Z3801. More testing is needed. If > these anticipated transmitters are merely close in frequency with no > actual energy at GPS frequencies, this looks like an excellent > business opportunity for someone to make and sell GPS antennas with > aggressive filtering. If they actually emit energy at GPS frequencies, > we are pretty much done for. I have seen the Youtube video of a > military GPS resisting jamming but I seriously doubt they would become > common place. > > > > ------------------------------ > > Message: 4 > Date: Wed, 2 Feb 2011 10:36:55 -0800 (PST) > From: Stanley Reynolds <stanley_reyno...@yahoo.com> > Subject: Re: [time-nuts] Lightsquared and a little math > To: Discussion of precise time and frequency measurement > <time-nuts@febo.com> > Message-ID: <76375.27763...@web30301.mail.mud.yahoo.com> > Content-Type: text/plain; charset=us-ascii > > Wonder if the clients of this network reduce power as cell phones do to > increase > battery life and reduce interference or they will use a dish on the fixed > clients, not that would help with interference from the sat. The web site > reads > like the sat will distribute the internet signal direct to the clients: > http://www.lightsquared.com/what-we-do/technology/ > > > Stanley > > > > ----- Original Message ---- > From: Chris Albertson <albertson.ch...@gmail.com> > To: Discussion of precise time and frequency measurement <time-nuts@febo.com> > Sent: Wed, February 2, 2011 12:09:07 PM > Subject: Re: [time-nuts] Lightsquared and a little math > >> Let's see, a 13 mile circle is pi r squared = ~ 530 square miles. >> 40,000 times 530 is ~ 21 million square miles. >> Wikipedia tells me that the area of the US is 3.79 million square miles. > > By the same logic, all of the office space in New York could not fit > in New York. But it does because they stack it 20 or 100 floors one > on top of the other. > > I suspect the areas will overlap with very dense coverage in urban > areas. Perhaps in some places there is 50 or 100 channels of coverage > and in others one or even zero. > > -- > ===== > Chris Albertson > Redondo Beach, California > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > > > > ------------------------------ > > Message: 5 > Date: Wed, 2 Feb 2011 10:45:22 -0800 > From: Chris Albertson <albertson.ch...@gmail.com> > Subject: Re: [time-nuts] Lightsquared and a little math > To: Discussion of precise time and frequency measurement > <time-nuts@febo.com> > Message-ID: > <AANLkTimJeWybt4OTX8cO=qPTkm=JSdKMLiaW=ngvf...@mail.gmail.com> > Content-Type: text/plain; charset=ISO-8859-1 > > On Wed, Feb 2, 2011 at 10:36 AM, Stanley Reynolds > <stanley_reyno...@yahoo.com> wrote: >> The web site reads >> like the sat will distribute the internet signal direct to the clients: > > People will hate this service. Going up to geo-sync adds a noticeable > and annoying lag do unavoidable speed of light round trip time of > flight. This is one reason the phone companies have been investing in > fiber for long haul. > -- > ===== > Chris Albertson > Redondo Beach, California > > > > ------------------------------ > > Message: 6 > Date: Wed, 02 Feb 2011 10:47:49 -0800 > From: Hal Murray <hmur...@megapathdsl.net> > Subject: Re: [time-nuts] Frequency multiplication > To: Discussion of precise time and frequency measurement > <time-nuts@febo.com> > Message-ID: > <20110202184749.dc01a800...@ip-64-139-1-69.sjc.megapath.net> > Content-Type: text/plain; charset=us-ascii > > >> Bottom line - there's a lot to look into, and they are unlikely to help you >> out. > > There are a lot of FPGAs used in DSP applications where the clock to the > front end ADC is critical. So I'd expect there would be some in-house > knowledge about this area. It may be that all the help you will get is > "Don't do that." > > -------- > > I think Altera uses PLLs. > > Xilinx uses DLLs, D for delay, a long chain of gates with an adjustable tap. > So the output signal will jump in time when the tap switches. > > FPGAs are designed for digital logic rather than clock hacking. I remember > some story from years ago about clocking troubles being traced back to input > threshold changes due to nearby outputs switching. I forget the details. I > think that particular problem was solved by moving all the output pins away > from the clock input pin. > > The smaller FPGAs are not expensive. It might make sense to dedicate a whole > chip to something like a clock mux. > > You could always use an external PLL and put the digital dividers in a FPGA. > > > -- > These are my opinions, not necessarily my employer's. I hate spam. > > > > > > > ------------------------------ > > Message: 7 > Date: Wed, 2 Feb 2011 11:13:49 -0800 > From: Pete Lancashire <p...@petelancashire.com> > Subject: Re: [time-nuts] Lightsquared and the FCC > To: Discussion of precise time and frequency measurement > <time-nuts@febo.com> > Message-ID: > <aanlktimt_bmsard0ofztstlkdammttqkg13aaco5m...@mail.gmail.com> > Content-Type: text/plain; charset=UTF-8 > > by then those in the FCC who ok'ed this will be working as a lobbyist > > -pete > > On Wed, Feb 2, 2011 at 7:32 AM, John Green <wpxs...@gmail.com> wrote: >> If the FCC weren't a government entity they would be called whores. >> This reminds me of the time several years ago when it was taking a >> year or more to get a grant for a 800 MHz license. The FCC granted >> thousands, yes thousands of requests from the company that would >> become Nextel all in one day. Quite often granting them a license for >> a frequency that was already licensed at the same location by someone >> else. All who objected were told to shut up and go away. Some years >> later when interference to public safety systems by Nextel got bad >> enough, the FCC made Nextel relocate those systems to different >> frequencies less prone to interference. But, they granted them access >> to the adjacent 900 MHz spectrum without having to file paperwork. >> When the first plane crashes because of Lightsquared interference, I >> hope the political s**t storm drowns those clowns. >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > > > > ------------------------------ > > Message: 8 > Date: Wed, 02 Feb 2011 13:17:12 -0600 > From: David Armstrong <armstr...@sedsystems.ca> > Subject: Re: [time-nuts] Frequency multiplication > To: Discussion of precise time and frequency measurement > <time-nuts@febo.com> > Message-ID: <1296674232.28891.28.ca...@sed192n90.sedsystems.ca> > Content-Type: text/plain; charset="us-ascii" > > FPGA's do not have good jitter performance. Both Altera and Xilinx have > app notes and specs on what to expect for jitter performance. > > > Particularly when using high speed DACs (like the ADI AD9739) the > technique used is to drive the DAC with a good quality clock, then the > DAC drives the FPGA. With high speed dac's like this there is often a > DLL used to optimize the data edges with respect to the clock. > > Similar techniques are used in the other direction ADC ._ FPGA. The > good clock is given to the DAC which presents the clock to the FPGA. > > The clock out of an FPGA may be good enough depending on what you are > using it for but check carefully! > > > > > > On Wed, 2011-02-02 at 10:47 -0800, Hal Murray wrote: >>> Bottom line - there's a lot to look into, and they are unlikely to help you >>> out. >> >> There are a lot of FPGAs used in DSP applications where the clock to the >> front end ADC is critical. So I'd expect there would be some in-house >> knowledge about this area. It may be that all the help you will get is >> "Don't do that." >> >> -------- >> >> I think Altera uses PLLs. >> >> Xilinx uses DLLs, D for delay, a long chain of gates with an adjustable tap. >> >> So the output signal will jump in time when the tap switches. >> >> FPGAs are designed for digital logic rather than clock hacking. I remember >> some story from years ago about clocking troubles being traced back to input >> threshold changes due to nearby outputs switching. I forget the details. I >> think that particular problem was solved by moving all the output pins away >> from the clock input pin. >> >> The smaller FPGAs are not expensive. It might make sense to dedicate a >> whole >> chip to something like a clock mux. >> >> You could always use an external PLL and put the digital dividers in a FPGA. >> >> > > > > > > ------------------------------ > > _______________________________________________ > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > End of time-nuts Digest, Vol 79, Issue 10 > ***************************************** _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.