Could New Clocks Keep Airplanes Safe From GPS Jamming? (bbc.com) 98
Geoffrey.landis writes: Over the last three months of 2024, more than 800 cases of GPS interference were recorded in Lithuanian airspace. Estonia and Finland have also raised concerns, accusing Russia of deploying technology to jam satellite navigation signals near Nato's eastern flank.
A group of British scientists -- dubbed the "Time Lords" -- are working on a solution: to develop portable atomic clocks. By carrying a group of atoms cooled to -273C on the plane itself, rather than relying on an external signal, the technology can't be interfered with by jamming. But the problem is that the equipment is still too large to be used routinely on planes.
The UK Hub for Quantum Enabled Position Navigation and Timing (QEPNT) was set up last December by the government to shrink the devices on to a chip, making them robust enough for everyday life and affordable for everyone. Henry White, part of the team from BAE Systems that worked on the test flight, told BBC News that he thought the first application could be aboard ships, "where there's a bit more space".
A group of British scientists -- dubbed the "Time Lords" -- are working on a solution: to develop portable atomic clocks. By carrying a group of atoms cooled to -273C on the plane itself, rather than relying on an external signal, the technology can't be interfered with by jamming. But the problem is that the equipment is still too large to be used routinely on planes.
The UK Hub for Quantum Enabled Position Navigation and Timing (QEPNT) was set up last December by the government to shrink the devices on to a chip, making them robust enough for everyday life and affordable for everyone. Henry White, part of the team from BAE Systems that worked on the test flight, told BBC News that he thought the first application could be aboard ships, "where there's a bit more space".
Solution? (Score:3)
By carrying a group of atoms cooled to -273C on the plane itself, ...
But the problem is that the equipment is still too large to be used routinely on planes.
Bigger planes? Or smaller atoms... :-)
Still Need External Signals (Score:3)
So, while having your own local, synchronized clock, will mean that you will not need to receive timing information from the GPS satellites you will still need to receive external
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Re:Still Need External Signals (Score:5, Interesting)
No, GPS does not work by triangulating.
The GP was almost correct, but got the word wrong. To be fair, though, in common parlance, the term triangulation is frequently used.
But you're right that the correct term is trilateration. Trilateration uses the distance from three (or more) fixed points to compute the position of something. Triangulation uses a combination of angles and distances to compute the position using only two fixed points.
For a triangulation example, if you look at the skyline of NYC and you compute the exact angle to the Empire State Building and the Chrysler building and you know the exact angles to both of them, you can accurately compute your location to one of two possible points even without knowing the distance to either of them by using trig, because you know how far apart the two buildings are.
With satellites, of course, the fact that GPS satellites are moving makes this problematic, and making any knowledge of the distance between the satellites even more problematic. And of course, GPS receivers tend not to be stationary, which makes measuring the angles way harder.
I have this vague memory that in an early design for GPS or one of the competing systems, they were going to have a small number of geostationary satellites, which could place you at one of two spots in the world even if the LEO birds all failed (as long as you're below about 81 degrees of latitude, which is to say not on Antarctica or in the Arctic Ocean, give or take), but I can't find any information about it, so maybe I'm imagining things.
But if you hypothetically did that, you could use triangulation more plausibly because of the fixed location of the satellites. Any vehicle crossing the equator would, of course, have a very bad time without a secondary frame of reference, such as a compass heading.
As an added advantage, you could make the antennas for a geostationary GPS alternative be highly directional (based on your last known location, the current time, and your compass heading, which can be supplemented with gyros for additional accuracy). That should make them much harder to jam.
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With GPS satellites, of course, the fact that the satellites are moving makes computing their angles problematic, and makes any knowledge of the distance between the satellites even more problematic.
Sorry. I edited that paragraph too many times and screwed it up pretty badly. Fixed above.
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With GPS satellites, of course, the fact that the satellites are moving makes computing their angles problematic, and makes any knowledge of the distance between the satellites even more problematic.
Sorry. I edited that paragraph too many times and screwed it up pretty badly. Fixed above.
Not to mention, the satellites are dealing with earth being an oblate spheroid, so they orbit in a not quite spherical fashion.
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The geostationary satellites are actually used (the three EGNOS satellites for example), but just as an augmentation system for improving the accuracy.
Not everyone is a Surveyor (Score:2)
The GP was almost correct, but got the word wrong.
No, I got the word right. I'm not a surveyor, I'm a physicist and the geometric sense of "triangulation" is measuring a point by forming triangles which you can do by either measuring angles or distances.
So as a physicist, commening on a physics article it's perfectly correct for me to use the term triangulation.
Triangulation (Score:2)
Understand before posting.
I do understand the principles behing GPS but being a physicist I was using triangulation [wikipedia.org] in the geometric sense of forming triangles to locate a point which you can do by either measuring angles or distances. Surveyors may limit the term to mean only using angles but I'm not a surveyor and so not limited their narrower definition. Hence, not being a surveyor and commenting on a physics article it is perfectly correct for me to say that GPS works by triangulation.
Please don't just regurgitate some surve
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Just knowing the time by itself is not a solution though so there is something missing from the article
There is indeed. This is all about developing quantum inertial navigation systems for real-world use. Clocks are just one part of it.
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GPS timing is based on the 'edges' of the signal. It was thought that as the signal was below the noise floor, that the edges would persist even in a jamming environment. It turns out that it's possible to mess with the edges if you know what you're doing (by transmitting an edge perhaps a microsecond before the real one - thus messing with the timing calculation in the receiver).
You actually don't need to receive a bit stream or decode anything to get your position by GPS. The bit stream contains informati
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Just knowing the time by itself is not a solution though so there is something missing from the article. GPS works by triangulating your position. The timing is used to time the arrival of the signals which you can then convert into a distance measurement. With multiple distance measurements you can then determine your position. So, while having your own local, synchronized clock, will mean that you will not need to receive timing information from the GPS satellites you will still need to receive external signals although perhaps simpler signals that are harder to jam because they don't have to contain timing information?
It is not triangulating. It is measuring the Time delay of arrival from the satellites. Each satellite has a stable atomic clock, and keeps tab on its own position.
If you receive one satellite signal, you can calculate your position on two potential places on earth. But to narrow that down, you need at least four signals received.
So with your four signals and their known locations, you take the satellites known positions, the different arrival times between their clocks and the receiver clock. and c
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It is not triangulating. It is measuring the Time delay of arrival from the satellites.
Right and you use the time delay to calculate your distance from the satellite. You then do that for several satellites to get your distances to them and then form triangles from those known distances to known points to get your position, a technique in geomtery called triangulation. Apparently that use upsets surveyors who have adopted a narrower definition of triangulation to only mean measuring angles - probably because it is useful for their profession to differentiate between techniques that measurre
Re:Solution? (Score:4, Funny)
smaller atoms
Do you have any idea how much those cost??
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Do you have any idea how much those cost??
It's not just the cost but the shelf life.
Muonic hydrogen is 200-fold smaller than normal hydrogen but has a half-life of only a few microseconds.
Very confused article (Score:5, Informative)
I realized the linked post about a very complex technology in an article is intended for a general audience but even by that standard it is very confused.
Chip scale atomic clocks have been commercially available for 20 years
https://www.nist.gov/noac/tech... [nist.gov]
and continue to improve in accuracy, durability, and reliability. Reading some of the commercial supplier listings to the point just before they stop and say "DOD customers call your sales rep" it appears that there are CSACs designed and qualified to be fired inside artillery shells so I think we can conclude they can be made pretty tough.
I think the article is trying to say that what is needed is an atomic clock that would fit in an aircraft electronics rack that also has the accuracy of a cold atom fountain clock, which is the current NIST/NPL/NRC standard. To which laboratories around the world say, please, bring it on. And all the national labs have been working on such for quite a while, not only NPL.
Re:Very confused article (Score:4, Insightful)
I tried to skim through the article and it seemed to jump around a bit. The thing I didn't see is how a more-accurate small-scale atomic clock replaces the need for GNSS. While yes, GNSS is based on accurate time, it's the reception and comparison of the time signals that give you distance to each transmitter (satellite) and so your current position. Having the time on board doesn't help with positioning.
Accelerometers are mentioned, which would be for inertial guidance... but if you have good inertial guidance, you don't care what time it is. And if you don't have good inertial guidance, the time still isn't going to help.
Re: Very confused article (Score:4, Interesting)
My thoughts go along the lines of how we used to navigate before GPS, namely by using a sextant combined with star charts at night, and looking at the angle of the sun during the day. All of which only work well when you have at least a vague idea of the current time and your current heading.
Buuut...Suppose we had some kind of automatic guidance system that combined artificial horizon with the relative position of celestial objects? All you'd need then to get good enough navigation would be a clock and a compass.
At a cursory glance, it seems like a very doable thing, possibly even fit it in an object about the size of a golf ball if not smaller, but I think such a system would be the bigger story than a clock.
Re: how we used to navigate before GPS (Score:2)
You went waaay to far back, we've had many electronic aids to navigation before GPS.
One such electronic aid to navigation that benefits from a very accurate clock is Inertial Navigation.
At aircraft speeds enhanced precision has proved an asset.
Re: how we used to navigate before GPS (Score:2)
That's called dead reckoning, and it didn't help Korean Air flight 007
Re: how we used to navigate before GPS (Score:2)
Oh and, apparently it's a thing:
https://www.bluewatersuperyach... [bluewatersuperyacht.com]
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Neither did the sextant, though - the 747-200 still had that.
Re: how we used to navigate before GPS (Score:2)
I doubt anything they had at the time would be comparable to what is possible today.
Re: dead reckoning (Score:2)
Oh come on now, you probably know better but hit reply before thinking.
Have yourself a cup of tea and do a cursory search for Inertial Navigation which I mentioned, okay?
One such system advertises "Up to 0.005 Roll & Pitch, 0.006 Heading and 8mm RTK Position Accuracy" and they point out its use in GPS denied environments.
Then you may want to look up RTK too.
Cheers!
Re: dead reckoning (Score:2)
It's called dead reckoning dude. Inertial navigation instruments are just automated dead reckoning. With a sextant, compass, and clock, you can actually determine your current location without needing to rely on previous measurements being correct. The further you travel, the more you accumulate drift.
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Thank you, I did not know that was how they did it on the Nautilus or all the following nuclear subs.
Guess I should have asked Jimmy Carter.
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My guess is that current GPS jamming doesn't just sprew garbage over the frequency, but rather is more strategic and results in a location being calculated, but it's the wrong location. In introduces error, so you might be say 5-10 or more miles off from where you think you are. Perhaps this is done by messing with the time that's broadcast, and could be corrected by having a referenced local time.
Many NTP servers use GPS for time. So if you get a position lock with GPS, and the time it calculates is differ
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While I think that's what they are trying to say it is also completely and utterly pointless. You don't need that level of accuracy to travel accurately. A standard rubidium oscillator will suffice.
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I share the confusion. No matter how good the plane's clock, the satellite signals need to reach the plane and not be spoofed. Hostile actors can jam the signals or potentially broadcast fakes. better clocks don't help these issues. I'd have thought they'd be working on lower cost better "laser gyros" and such, so that the planes could reliably use internal navigation when the GPS is iffy. But Time Lords wouldn't be the right title for folks working on better / cheaper internal guidance.
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I share the confusion. No matter how good the plane's clock, the satellite signals need to reach the plane and not be spoofed. Hostile actors can jam the signals or potentially broadcast fakes. better clocks don't help these issues.
Yes, they do. If your altimeter is accurate, an on-board clock means you only need to acquire signal from two satellites, presumably the two with strongest signal. The fewer satellites you need to acquire, the harder it is to jam.
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Or connect to a half dozen or more and make sure more than one pair (or triplet) all agree on location.
Or use a secondary method like VOR, etc. and compare results vs. GPS.
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>Chip scale atomic clocks have been commercially available for 20 years
Not quite. I remember looking around when NIST first announced that research, but it took several more years until they were commercially available. The first one you could actually buy was the SA.45s in 2011. source [si.edu]
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Have you actually looked at those chip scale atomic clocks? I happen to have one on my desk right now. It's not the latest model but it's not that old either. 100ns resolution PPS in/out. Nowhere near good enough for this kind of application. They get better as you ramp the cost up, but not enough for this kind of thing unfortunately. The chip scale ones are for applications where 100ns is fine or you want a long term stable frequency reference, because again over very short periods like the ones needed for
Just like longitude (Score:5, Insightful)
As the article mentions, the parallels (haha) to John Harrison from 300 years ago are strong. He was an Englishman who solved the problem of finding how far east or west ship was, even in the middle of the ocean, by putting accurate clocks on ships, just like the UK scientists.
Dava Sobel covered it beautifully in the book Longitude, and I can highly recommend the illustrated version.
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I think the idea is to use GNSS most of the flight, but have a backup system that can cover periods of jamming, and sanity check the GNSS data coming in. Sync it to GNSS and then free run through periods of no/questionable reception, for say a maximum of 6 hours or something.
Difference (Score:2)
BuckyBalls (Score:2)
BuckyBalls/Fullerenes would be accurate enough to allow for several mm level system location accuracy that requires very little power to maintain.
It will just flash 12:00 (Score:3)
Time is just one variable (Score:5, Informative)
GPS requires 4 satellites because it has to get you latitude, longitude, altitude and time, so you need 4 satellites to provide you with a solution for 4 variables. More is better, as it gets you an over-solution which lets you get better accuracy if you get a better constellation of satellites.
But having an atomic clock on board only resolves the time variable, so you're still needing 3 satellites to provide you with the lat/tong/altitude. And it's not great, because even at airliner altitudes and speeds, that atomic clock will drift, thanks to Einstein.
The INS (inertial navigation system) is still reasonably accurate - given most airliners will have ring laser gyros to measure acceleration and is technology already present today. Sure it drifts, because you get the fun of a double integration, but the INS errors are remarkably small - generally speaking a couple of nautical miles drift over the course of a 8-12 hour flight.
If you slaved the INS to the GPS then GPS jamming remains a non-issue since the INS can supply the positional information while GPS loses lock. And with a little computation smarts, you can detect if GPS is being jammed in a more sophisticated manner (where false information leads it to being off-course). Remember, the INS is quite accurate, so there's no reason for GPS position to differ very much when you compare positions. If you're calculating how the INS is drifting, it should be reasonably small between updates, and the absolute drift should remain small. If it suddenly jumps perhaps the GPS is receiving a spoofed signal.
But spoofing is a far more sophisticated attack than just mere jamming.
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And it's not great, because even at airliner altitudes and speeds, that atomic clock will drift, thanks to Einstein.
Aircraft know their speed and altitude pretty well, even without GPS, so this would seem to be easy to correct for. Wind would be the largest uncertainty, because it makes airspeed different from the ground speed, but I guess you could still reduce the atomic clock drift due to these effects by an order of magnitude.
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You only need three - facepalm.
On top of that the timing is in the signal anyway.
Because: oh, we use the timing to calculate our position and not the angels.
A fourth satellite is nice: so we can pick 3 with the strongest signal.
Jamming, is not changing the information the satellites sent you.
It is just a radio signal stronger than one/some of the satellites. Your receiver picks the 4 or 5 strongest signals, and they tell you: I am at X,y, z ... and so on. Can be a single sender just telling you bogus inform
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Inertial navigation isn't accurate enough for long distance navigation, though the new quantum IMUs being developed could finally change that.
VOR and ADF both use radio signals which are just as easy to jam as GPS signals and neither one is suitable for precision approaches the way GPS can be used.
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Inertial navigation isn't accurate enough for long distance navigation
Of course it was. It was used by the jets to cross the atlantic and pacific. It was a perfectly cromelent system.
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Inertial navigation isn't accurate enough for long distance navigation
Of course it was. It was used by the jets to cross the atlantic and pacific. It was a perfectly cromelent system.
Jets?
In early 1953, the government convened a meeting of researchers in Los Angeles to discuss the possibility of inertial navigation.
"Doc" Draper and his MIT team stuck their prototype INS unit in a B-29, but had no time to test it before flying non-stop from outside Boston.
After 2,500 miles of flying with no input from the pilots, it was only 10 miles off.
Draper went to the meeting and said that yeah, it was possible, since he'd just done it.
I feel sorry for whatever presentater followed him.
Re: Reinventing the wheel, again... (Score:2)
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Look, I have a book, about astro navigation.
It helped me a lot, because the fucker who sold me the boat, did not mention, that one leg of the navigation table to short.
So, I opened my book, about 35% into the boring part, and pushed it under the leg of the table. Now I have a perfect navigation table, with perfect leveling and perfect utilization of my astro navigation almanac.
Oh, why type so much?
Inertia based Navigation does not work like you think it works. It was part of many things that were used.
With
The Donald and The Melon say "Fake News" (Score:3)
No, I'm sure Zelensky did it - my country's president tells me we don't need to worry about Russia doing bad things.
Ah, what? (Score:2)
The problem is not that planes and ships lose GPS-provided _time_. The problem is that they lose GPS provided _position_ and vectors. How on earth is carrying better clocks supposed to help with that?
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For inertia navigation, you do not need better clocks.
And it has nothing to do with GPS anyway.
We have laser based inertia based tracking since 50 years.
Obviously: it can not recognize if a wind pushes you around.
Point is: that article has nothing to do with GPS. My local clock being worth or better: does not change at all that some super beam identifies itself as satellite A and is pumping 5 times the radio strength on me, as the real satellite would do.
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For inertia navigation, you do not need better clocks.
And it has nothing to do with GPS anyway.
We have laser based inertia based tracking since 50 years.
Obviously: it can not recognize if a wind pushes you around.
Ah, what? Does the wind magically bypass acceleration and can push you around without applying that?
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Ah, what? Does the wind magically bypass acceleration and can push you around without applying that?
Yes.
As it is a constant forced, and your inertia tracking system only gets the first push of it, and not the constant application.
And bottom line: the force is to low to be recognized anyway. When you lift off from an airport, the inertia tracking only measures your acceleration on the runway (actually, it does not "measure" that, it knows it from the engine power). And the short nudge when you lift of and lo
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Ah, what? Does the wind magically bypass acceleration and can push you around without applying that?
Yes.
As it is a constant forced, and your inertia tracking system only gets the first push of it, and not the constant application.
Ah. I see. You failed physics 101. Constant force causes acceleration, which inertia tracking measures, or it does not because of
drag (i.w. equal counter-force) , then there is no acceleration and inertia tracking measures no change in speed.
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No, the constant force does not cause acceleration.
Perhaps you should fly or sail once.
It just changes the vector of your travel over ground.
E.g. you have a constant side wind of 40mph from the right. After 1h flight you are 40m "left" from the point you aimed for.
In water that is much less as the water does not allow you to drift 40mph "to the left" ...
then there is no acceleration and inertia tracking measures no change in speed.
Inertia tracking only tracks acceleration and not speed. And in general, only
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https://en.wikipedia.org/wiki/... [wikipedia.org]
P.S.
What does 101 actually mean?
In Germany we have I, II, III and so on. 101 makes no sense at all.
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What does 101 actually mean?
In Germany we have I, II, III and so on. 101 makes no sense at all.
That is the academic beginner's course. The one that everybody is expected to pass. You also failed to understand what an accelerometer measures. Here is a hint: It measures acceleration. No acceleration - no change in speed.
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No acceleration - no change in speed.
Yes, but for that you need a frame of reference.
And if the whole frame is accelerated: you measure no acceleration.
That is why wind drift or ocean currents are so difficult to measure.
With modern laser interferometers you could do that. Span a few yards of fibre in every relevant direction, then you could do it. However the current systems only measure how your ship/plane is tilting/rotating. Not how the current is suddenly increasing from 5knots to 5.1knots. And half a
Before GPS (Score:3)
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Existing Comercial Inertial Navigation Systems (Score:2)
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British scientists -- dubbed the "Time Lords" (Score:4, Funny)
"the equipment is still too large to be used routinely on planes."
Just make the plane bigger on the inside than it is on the outside.
TFA is not particularly great. (Score:2)
1. MEMS clocks with microsecond-per-day accuracy are commercially available and they're getting better.
2. 1 ns drift = 30 cm position accuracy.
3. You still need signals from known positions to triangulate your location.
So while jamming GPS is trivial, the alternative is using other sat networks or building terrestrial radio beacons. Variations on the same problem. Just having accurate, portable clocks does not help.
This article boils down to: UK is working on portable atomic clocks, just like everyone els
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Just having accurate, portable clocks does not help.
This.
GPS does NOT depend on an absolute time accurate clock at the receiver. Or my cheapo handheld GPS could not exist*. What it does need to do is to accurately measure the time difference between several received satellite signals. And that is a (relatively) easier thing to do. Assuming that no one is screwing with the received sat signals. Which is in fact what is going on.
The terrestrial beacon idea is a good one. Ground-based 'virtual satellites' can be set up near critical areas like airports to giv
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And if anyone tries to jam them, the signal strength will make them sitting ducks for an AGM-88.
Russia is already fucking with GPS signals. But apparently they're the good guys now and everyone should bend over backwards for them and give them free land because apparently that's the best thing to do now.
There are other solutions (Score:2)
I know this is going to get modded as flamebait ... but there are still pilots out there that remember how to fly without satellite data. This isn't lost knowledge that needs to be dug up by an archeologist.
There are perfectly serviceable land based navigation aids, and looking out windows....
We don't need new tech to do this.
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Not modded flaimbait.
Modded idiot.
We are not talking about "somewhere on the ocean" with one island left and one right and land behind me, and I expect to see land in 15 minutes in front of me. Oh, I see the land already? I am not where I was thinking I am ...
We are talking about the most busiest air traffic zones in the world. Yeah, Frankfurt for instance: one plane per minute landing ...
The planes want to know at least on 100m/yard resolution where they are. You only have two people in the cockpit to look
Maybe solve with very different satellite tech? (Score:2)
Instead of a unidirectional signal, use something bidirectional like Starlink satellites. Use beamforming across multiple satellites to punch through any interference. Configure the satellites to aggressively crank up the transmission gain and the number of satellites participating in the beamforming if it loses the signal from an in-motion airplane until it is able to get confirmation that the aircraft is receiving the signal. Provide a switch to keep that feature enabled while on the ground if you're
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itself to recognize unexpected signals and cancel them out so that the receiver hardware never sees much of the jamming signal. Ever god blinded by the light of the headlights of a car on the opposite lane? That is jamming.
There is no way to cancel it out.
Sure there is. Phased arrays let you effectively point an antenna in a specific direction so that the vast majority of the signal comes from or goes towards that direction, and all other directions are weak by comparison. Use multiple antennas. "Point" one antenna towards the interference source. Invert the phase. "Point" other antennas towards the desired sources. Sum a portion of the inverted signal with that, calculating the correct amplitude based on the expected off-axis rejection of the other an
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I'm fairly certain that you are incorrect [quora.com]. There's no difference between retiming signals going to multiple antennas and retiming signals coming from multiple antennas except in terms of the hardware used to do it.
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For receiving, the antenna is PASSIVE.
There is nothing you can modify to change anything about receiving signals.
If I beam some energy on your antenna, that is *louder* than what you expect, you do not get what you expect.
Are you seriously so stupid?
A phased array antenna is not one antenna. It is multiple antennas.
You achieve beamforming while receiving signals by delaying the signal from several antennas that are some distance apart. Because of the distance between the antennas, the signals arrive at the antennas at different times. If they're coming from a source that is closer to antenna A, they arrive at antenna A. If they're coming from closer to antenna B, they arrive at antenna B first.
These signals are waves, which means if you add two cop
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A phased array antenna is not one antenna. It is multiple antennas.
Sure.
Multiple antennas that work as one unit.
By adding a delay to compensate for the distance between antennas, you're making signals from a specific direction stronger by making them arrive at the same time. And you're simultaneously making signals coming from every other direction weaker by making them arrive at different times. With enough antennas arranged three-dimensionally, you can create a significant amount of off-axis rejection.
Wel
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Well, then publish your papers and farm in your PhD. and Nobel Prize.
What I'm talking about isn't some bizarre, exotic, rare idea worthy of a Nobel Prize, but rather a pretty common piece of technology that you almost certainly have in your Wi-Fi access point unless it is over a decade old. That's how small these phased arrays can be up in the GHz range.
How do you want to place a 3 dimensional phased array antenna - that can filter signals - into something that fits into an airplane ???
Antennas are never *in* an airplane. You would lose too much signal strength. They're in a pod on top (satellite) or on the bottom (VHF, etc.).
As for fitting, the size of a phased array is proportional to the operating fre
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Sorry,
"phased array antennas" can not be "pointed at something" to receive only signals from there.
The can only sent signals into specific directions.
You can jam them just like any, normal antenna, which is not a "dish".
You are completely wrong. You learned something wrong, where ever you learned it. Perhaps a SF movie?
The only way you can receive from or transmit to a satellite without physically pointing a dish at it is with a phased array. transmit yes, receive no. And you need multiple face arrays, as t
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Sorry, "phased array antennas" can not be "pointed at something" to receive only signals from there.
The can only sent signals into specific directions.
Okay, you're attacking a straw man here. I did not say "receive only signals from there". There's no such thing as receiving signals only from a given direction. You can *reduce* reception from other directions, but as long as you're going through the air, it is impossible to make it zero.
You can jam them just like any, normal antenna, which is not a "dish".
You can jam a dish, too; it just takes more power than with a non-directional antenna. A dish is just another directional antenna, which means any off-axis signal's strength is weakened compared with an on-axis signal.
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Yes, "some" air planes use phased arrays to receive information.
But that does not make them jamming proof.
It is just an antenna.
You are mixing something up.
Start reading here, perhaps: https://en.wikipedia.org/wiki/... [wikipedia.org]
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But that does not make them jamming proof.
I never said it did. But you absolutely can use phased arrays to massively reduce the received strength of a signal coming from a particular direction, and jamming is by its nature only going to be coming from a single direction, realistically. So you can improve the SNR considerably by steering nulls in the direction of the interference signal, effectively making that the weakest direction for reception, albeit at a cost in signal strength from other directions.
More discussion of this here [secretprojects.co.uk].
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Make that absolutely certain [sciencedirect.com].
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Yes,
absolutely certain.
Are you too stupid, or just too lazy to read the text behind the links you post?
The article you link is about forming beams from phased array antennas ....
Your reading comprehension sucks.
Re: (Score:2)
Yes, absolutely certain.
Are you too stupid, or just too lazy to read the text behind the links you post?
The article you link is about forming beams from phased array antennas ....
Your reading comprehension sucks.
Right there on the page:
"Receive beamforming has advantages over transmit beamforming. A conventional transmit beamformer can focus at only one focal point per transmission. A receive beamformer can achieve focusing at all depths, ideally. In order to understand how this is possible, refer to Fig. 7.14. The path of a pulse echo from a point z on axis to element n in an array has a propagation delay pn. If a compensating delay dn is added to the propagation delay to obtain the same constant overall time for each element channel, then all the pulse-echo signals will be aligned in time and can be added in synchronism. This approach is called a “delay and sum” beamformer. An additional advantage is that the compensating delay profile or electronic lens can adapt for each depth. Depending on how fast the electronic lens can be reconfigured relative to the digitized pulse-echo data streaming into the beamformer determines the number of individual depths at which the refocusing can occur. This process of reconfiguring the receive focusing with depth is called “dynamic focusing.” This focusing is compensating for diffraction which occurs in reverse for reception."
Hell, even in the Wikipedia article for beamforming [wikipedia.org], it says, "Beamforming or spatial filtering is a signal processing technique used in sensor arrays for directional signal transmission or reception.
Yes, you absolutely can do beamforming on the receiver end.
Works until GPS jammers improve (Score:2)
The technology maintain a local precise time with two benefits:
- the distance from all true GPS satellites is now determinable, removing uncertainty; et least, one less GPS satellite is needed
- GPS jammers with grossly inaccurate time reference are weeded out
So my best guess is that countermeasure won't work against GPS jammers with an accurate time base, or smart enough to align their time base to other GPS satellites.
Why not work on spoofing resistance instead? (Score:2)
GPS spoofing and jamming originates from sources beneath the aircraft, Russia doesn't have jamming satellites in orbit AFAIK. At least not yet. All genuine GPS signals always come from high above the horizon. All sources of interference come from way below. There must be a way to exploit that fundamental difference to distinguish between genuine signals and all noise. Array receivers should be able to tell where in space a signal is coming from and with a little additional logic could determine where the ho
Commerical Atomic Clocks Already Exist (Score:2)
There are old HP/Agilent/Kesite cesium clocks on ebay that are/were used in electronics.
Cat got your tongue? (something important seems to (Score:1)