[time-nuts] [time nuts] Frequency Multiplication
Sean M. Bietz
smbietz at gmail.com
Wed Feb 2 23:54:31 UTC 2011
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-request at febo.com wrote:
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> Today's Topics:
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> 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.chris at 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 at febo.com>
> Message-ID:
> <AANLkTimK_bzjZS03n7v2PJPPNmD_yfaGRRd_y=2gMBYG at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> On Wed, Feb 2, 2011 at 10:02 AM, paul swed <paulswedb at 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" <lists at rtty.us>
> Subject: Re: [time-nuts] Lightsquared and a little math
> To: "'Discussion of precise time and frequency measurement'"
> <time-nuts at febo.com>
> Message-ID: <60B8A8A8E6584D2CB3AFFAD4F5BF95E7 at 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-bounces at febo.com [mailto:time-nuts-bounces at 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 <lists at 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
>>
>>
>>
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>
> ------------------------------
>
> Message: 3
> Date: Wed, 2 Feb 2011 12:28:11 -0600
> From: John Green <wpxs472 at gmail.com>
> Subject: Re: [time-nuts] GPS receiver jamming
> To: time-nuts at febo.com
> Message-ID:
> <AANLkTim299pGx6veqUQh_T4TC7qkcaG-RkTFRFZJZ_Ga at 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_reynolds at yahoo.com>
> Subject: Re: [time-nuts] Lightsquared and a little math
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID: <76375.27763.qm at 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.chris at gmail.com>
> To: Discussion of precise time and frequency measurement <time-nuts at 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
>
> _______________________________________________
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>
>
>
> ------------------------------
>
> Message: 5
> Date: Wed, 2 Feb 2011 10:45:22 -0800
> From: Chris Albertson <albertson.chris at gmail.com>
> Subject: Re: [time-nuts] Lightsquared and a little math
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID:
> <AANLkTimJeWybt4OTX8cO=qPTkm=JSdKMLiaW=NGvf4uf at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> On Wed, Feb 2, 2011 at 10:36 AM, Stanley Reynolds
> <stanley_reynolds at 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 <hmurray at megapathdsl.net>
> Subject: Re: [time-nuts] Frequency multiplication
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID:
> <20110202184749.DC01A80003B at 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 <pete at petelancashire.com>
> Subject: Re: [time-nuts] Lightsquared and the FCC
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID:
> <AANLkTimT_BMsARd0OFZtsTLKdaMMttQKG13AacO5MUNE at 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 <wpxs472 at 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 at 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 <armstrong at sedsystems.ca>
> Subject: Re: [time-nuts] Frequency multiplication
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID: <1296674232.28891.28.camel at 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.
>>
>>
>
>
>
>
>
> ------------------------------
>
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