Evolution of GNSS -- Taoglas and Mouser Electronics
[Music] where would we be without gnss or GPS completely and utterly lost well I would be for absolute certain I'm one of those people that turns the wrong way always so if you see me walking one way most likely you'll want to go the other way but how has gnss and GPS evolved over the years and what kind of improvements are we seeing these days well let's talk about it hi I'm Emilia Dalton host of chalk talk in this episode of chalk talk Pat Frank from tow glass and I explore the details of multic constellations gnss systems we also investigate the key characteristics of antennas and how you can future prooof your gns s design with tow glasses and tenna Solutions and before we get started don't forget to click that link there you can find even more information about this topic from doww glass hi Patrick thank you so much for joining me thank you so we're talking about the evolution of gnss today but let's start at the top Patrick what kind of benefits does multiband gnss bring to the table right yeah so there's really like a couple Main benefits that come when we talking about multiband gnss and really it's accuracy and reliability and as you go through a number of different applications you know you can weigh the differences between you know is this important for me or or not so if we look at certain applications like an autonomous vehicle or automated driving car it's pretty clear that we want not only accurate position but reliable position and as we go through different applications maybe wearables you know we really appreciate having a more accurate position and as we go to other applications you go to something like an asset tracker then really maybe you don't need the same kind of highly accurate or highly reliable position there's another benefit that comes with multiband gnss and that's more accurate to more reliable timing and this is maybe something that kind of hides in the background in a lot of applications I think a good example for me is for 5G so if we go to a look at 5G one of the features that was brought into 5G was this kind of close coordination between base stations but one of the enabling Technologies that's required for that is to have really accurate really precise timing but not only that 5G we really depend on our cellular networks quite a bit so having reliable timing also is really really important so I look at as accuracy and reliability so Patrick walk me through the details here this ensures that redundancy is built in correct right yeah exactly so this is kind of tangential to multi band and there was a time when we talked about bands in terms of constellations and that's kind of just got things a little bit confused but here really what we're talking about this is a secondary thing so constellations is GPS Galileo glass and Betto so having four different whole sets of satellites in the sky that are available for us to use for our location and what does that do for us wow that gets us all the benefits of having multiple so many different satellites in the sky so reduced signal acquisition time it gives us Improvement because of just having that in a many number so we get you know reduction of problems caused by obstruction so if the three GPS satellites are are being obstructed maybe you have for Galileo over in another part of the sky that you can use and then just having more satellites spread across the sky gives you better geometry which we call dilution of precision so just better geometry for things and then all that adds up to improved position and time accuracy in addition to having some redundancy so if the GPS system is down for example there's multiple there's three other constellations available for that position and time so can you give me an example of this kind of system sure yeah the GPS is a great example we'll walk through how this works and what this looks like so when we look at GPS GPS satellites have been up for quite a while and all of the satellites to date have had one band One frequency man that's L1 1575.42mhz all of them have that and that's kind of the classic GPS frequency if somebody says GPS and you think of a frequency this is really the one 1575 so it's a legacy it's on all it's not going anywhere it's going to stick around for a while it has civilian signals has also a couple other signals available to it and then really when we look at the Technologies we look at the receivers available and what kind of accuracy kind of focusing on that part of it about the best we can do is we call it a 3 meter accuracy and that's taking everything that we know for a standalone GPS receiver gets us about 3 meters of accuracy all right how do we get better accuracy than that because I think for some applications going back to that autonomous vehicle like that's too big of a range like that's being in one lane or another Lane so we really need something better than that so how do we do that well it turns out that actually a big part of a lot of that error that comes in is from actually a part of the atmosphere called the ionosphere and really there's maybe a couple ways of dealing with that but one of the best and most reliable ways of dealing with that error is by adding a second frequency and that's where we get this multiband concept and that first second frequency was L2 1227 mahz this has been on all GPS satellites that are in use right now have L2 available and the use of these two signals allows us to almost cancel out that error that was introduced in the ionosphere and that gets our accuracy down to that 1.5 M so that's much better now we're talking about a single Lane of driving rather than am I in this lane or that L now as part of modernizing GPS new satellites that are being put into orbit have an additional third frequency and that's L5 that's pretty close to L2 and it's 1176 MHz so this is again available at all newer satellites and really what it was intended for for was it was looked at and they said okay we have some pretty important applications Aviation is actually what they had in mind and let's make sure that we can have a signal that's as reliable stable and provides the most resilient position possible so that's where L5 comes in it has advantages over L2 it has more power and it has a higher gain so there's just more available from L5 than there is from L2 however both cases L5 or L2 you still need to use them together with L1 to get that improved performance now you can use all three together some receivers do that and then you can kind of going back to that last topic you can add in additional constellations and that can further improve the picture now that's 1.5 M how
do you get even better that's where these other two frequencies come into play the first one the both of these when we were talking about further improving accuracy really what we have to do is we have to supplement the signals that are coming from those satellites like GPS with additional things we call them correction services and that can come from a few different places one can be from this L band so this is a signal that comes from satellites also it comes from different satellites than GPS or Galileo or glown as or bet they provide different data that help us correct the signal even more and that can get us into the decimeter range and there's a similar kind of signal that will be available at E6 this is from Galileo only it's called a high accuracy service and we'll provide again not locating data but Corrections data now there's an ultimate kind of Corrections available and that's called rtk or realtime kinematic and with that that you can get down to a centimeter level kind of positioning wow okay so Patrick what impact did these other bands have on antenna and RF Solutions right yeah exactly there's no such thing as a free lunch is there and so the left antenna that we're looking at is our CBP 25.4 that's a 25 mm Square 4 mm stick that's kind of your classic patch antenna that we think about and associate with GPS that's single band quad constellation supports GPS Galo glow as and bet but it's single band it's L1 only now let's say we want to use L2 and L5 that gets us to the antenna over there on the right that's our gbdf 512a that's a L1 L2 L5 supports all four constellations but now we look at the size that's a 50x 5050 by 12 mm quite a big difference and then looking at complexity we can see that increase in complexity also looking at a similar kind of antenna we can see that with that antenna there's more pins there's things we have to add we have to add hybrid couplers we have to have amplifiers filters and now that's at two different bands so here we show our hp24 510a which is a L1 L2 I believe and we have two hybrid couplers our tfm1 100a frontend Electronics module many different things are pulling together here to enable that higher Precision so many different parts so the idea of future proofing is crucial here right so how do you guys help with this issue right yeah exactly so having you know a solution and implementation a positioning solution that really works for yourself for the long term if you stick with a single band is that really going to provide the the user satisfaction is that going to enable the the future solutions that you have in mind for your application or are you going to need something more and if you look down the road do you need something more that very well might look like adding multiband gnss receiver and all the things that go with it so typical for that single band design again that 25x 25 by4 patch antenna maybe you have similar kind of thing with an active antenna on it's offboard but that's really locked you into that single band topology now if you think you might want improv positioning more resilient timing that can get you cleaner signal better accuracy so looking at what what are my options now and do I want dual band triple band all the bands well that's just it so prices are coming down the technology for a lot of these things especially the receivers compared to 10 15 years ago the receivers are in a totally different spot and looking at our antenna Solutions we have solutions that are single band we have antennas that are dual band triple band support all the bands so whatever you need and many different size factors so we have solutions that work for whatever your device whatever your application we probably have something that slots and can work and help to provide a future proof solution for you because all these new bands aren't going to wait anytime soon so what kind of antennas does Tow glass offer so as mentioned we have a wide range of antennas available for single band or multiband gnss and really what we're trying to do is we're trying to to make sure that customers of ours in many different applications can find a product of ours find an antenna that meets with their requirements for position robustness and performance in the package that they're looking for so we have everything at the very low end of the scale the chip intenance we have the ggbl A.1 125a it's linear polarized antenna but it's very small it's very high efficiency very good for very compact installations very compact applications that are made in Mobile but you want to get the benefit of for example using L1 and L5 you can get a lot of that benefit with a very simple chip antenna moving up we have flexible PCB antenna again linearly polarized you have a few different sizes passive and active and again this works for a lot of applications you want to peel and stick inside of a larger housing or we have the classic patch antennas we have dozens of different patch antenna sizes that support different bands slightly different form factors different ways of applying it passive and active and really this is the classic that most people will land on for an embedded solution but we have whatever the band configuration that you need we have an option for it moving up into larger maybe you need something that's more robust that might go into an external or some piece of Machinery or some sort of autonomous vehicle we have a few different external options and here's a couple we have a cross dipole option the XA hp50 that features very low cross polarization very good antenna performance and a pretty compact package and then going up we have quad helical antennas that have excellent circular polarization Purity excellent performance omnidirectional again passive or active so whatever it is the application we strive to be able to scale to the size cost and performance that you need so Patrick what are the key characteristics of antennas that we should keep in mind right yeah exactly so traditionally with gnss single band as Solutions youd really focus on antenna gain and maybe Axel ratio maybe now we're going to higher Precision multiband you're really kind of taking a closer look at maybe how do I get better performance out of my device then you have to look at a few different variables few more different characteristics so antenna gain is probably still the maybe the most important characteristic that you have to keep an eye on gain or efficiency depending on if you have fa mobile application then maybe you want to look at the efficiency more but most applications you want to look at antenna gain that's in DBI or dbic secondly is Axel ratio so this is a description of how pure is the circular polarization of this so the signals that are coming from the satellites are circularly polarized and ideally the antenna is receiving in that same way so the acceler ratio is a measurement of that and Zer DB is a perfectly circularly polarized antenna and linear antennas doesn't even matter you just don't even look at it but for a lot of antenas especially if you're really trying to get to that decimeter trying to use rtk that a ratio can really start to have an impact and that can also kind of have a knock on secondary effects where having a good clean pattern will start to have effects on these other characteristics so phase Center offset hear this a lot you see this a lot on a high Precision antenna data sheets and what is it really mean well the phase Center is where the gnss receiver actually calculates his position so when it gets a position a three-dimensional coordinate that's actually the position of the where it thinks it is with the phase center of the antenna or PCO and now no antenna is perfect so that phase Center offet might be off a little bit from the geometric center of the an so PCO how does that change that might actually change as you look at it over the course of the sky so as a satellite moves across the sky that might actually impact where the receiver actually calculates its position that's the phase Center variation lastly is something called group delay variation sometimes called gdv and this is how the antenna uh how the filters distort the signal gnss signals in time and that can cause a distortion in the position so all these factors together really come to bring together the ultimate accuracy and often we'll use this 2D RMS term which is where if you have all the points the calculation over a certain period of time you draw a ccle around 95% of them and that's your actual accuracy so there are passive and active antennas as well right right yeah exactly this can cause some confusion because we have both available and we'll get this question a lot you know which one should I use should I use a passive antenna or should I use an active antenna and I look at it so if you look at your receiver so you look at that first and if your receiver already has an LNA or low noise amplifier inside and your antenna is pretty close maybe it's on the same board you just up Trace connecting the two and you're probably okay to just use a passive antenna then you avoid a lot of the complexity that comes with having an active antenna and that that will be true for single band or multiband now if your receiver does not have an LNA or low noise amplifier inside then you definitely in active an there's there's no question about it no matter how close or far away your antenna is or regardless of whether there's an LNA inside the receiver or not then if your antenna is pretty far away from your receiver then you you really want an active antenna also just to avoid any additional losses or distortions or things like this that can come from having a long cable for example excellent well Patrick I think that's all I have time for today thank you so much for joining me thank you so much for having me and before we go you didn't forget to click that link did you there you can find even more information about this topic from tow glass for chalk talks I'm Amilia Dalton from E journal.com for more chalk talks head on over to the chalk talk section of e Journal you can't miss it it's right across the top or or head on over to YouTube youtube.com/ ejournal
2024-12-18 20:58
