garrya Posted January 2 Share Posted January 2 So the HTS pod on F-16 (or all RWR) can find target azimuth but no information on elevation, there is no information on whether target is at lower or higher altitude. but what if I roll the aircraft to the side?. Like with half a roll while pointing the nose toward the emitter. Wouldn’t the sensor oriented in the way that allow me to find target elevation, and thus based on my own altitude, I can calculate distance to target? Link to comment Share on other sites More sharing options...
Milker Posted January 2 Share Posted January 2 Hi! Well, who knows! That would be a nice tip but I don’t think it works that way… it would also need an axis change on the searching radar!!! I don’t know if anyone here knows how it really works and it’s limitations, and at least some of “how it really works” must be classified! Good hunting Link to comment Share on other sites More sharing options...
Rosly Posted January 5 Share Posted January 5 On 1/2/2024 at 6:32 PM, garrya said: So the HTS pod on F-16 (or all RWR) can find target azimuth but no information on elevation, there is no information on whether target is at lower or higher altitude. but what if I roll the aircraft to the side?. Like with half a roll while pointing the nose toward the emitter. Wouldn’t the sensor oriented in the way that allow me to find target elevation, and thus based on my own altitude, I can calculate distance to target? This is not how those sensors work. HTS is not RWR and their principle of operation is different. TLDR it is already done, but measurement error is huge and you cannot get exact location by just single measurement. The basic principle on how HTS work is phase detection and position triangulation. Inside HTS you have a lot of antennas (the phase array matrix to be exact) and based on phase difference for received wave between those antenna reception points, you calculate the bearing and elevation to emiter. The bearing and elevation calculation always have some error because of the electronics limitations, noise, reflected signals, Doppler effects and other signals in the air on the same band which you cannot completely filter out (to put it simply they add the phase noise to your measurement). So you have both, the exact one you asking for, but elevation error is much higher as its relative error to range is much higher. There are also much more reflection in elevation than there are in azimuth. Never the less, single measurement is not enough and it is like giving you generic area where the emiter is. This is how RWR work and where it's functionality ends. It simply display you the bearing and for elevation it can tell higher or lower than your plane as this is max of it's precision. If you want to learn more how old EWR works here is a nice video The RWR is simply phase detector where front and rear antennas are one axis, and left wing and right wing antena are another axis. Than (in case of early RWR) those phases were plotted on a scope and give you the visualization of a bearing. There is no way you get elevation other than leaning on a wing (antennas are directional) so you will se if signal will decay. Going back to HTS. At this point you need to think you have single 3D vector to emiter as HTS has this matrix phase array (which has hundreds of antennas in it). The error for it's measurements (where you project a cone from vector and error) give you 5nm flat space at 30-40 nm of distance (more or less). So now you should figure out why we have PGM levels! The longer you fly, and the greater the angular distance from all the measured 3D vectors you acquire, the more precise the location will be. This is basic method for decreasing error came from measurement theory. The error of the measurement can be decreased if you have a lot of them. And even more, in scope of triangulation, the bigger the difference in aspect to the measured location, the smaller the error of the projection cone will be. And this is how HTS is working. 1 Link to comment Share on other sites More sharing options...
garrya Posted January 6 Author Share Posted January 6 13 hours ago, Rosly said: This is not how those sensors work. HTS is not RWR and their principle of operation is different. TLDR it is already done, but measurement error is huge and you cannot get exact location by just single measurement. The basic principle on how HTS work is phase detection and position triangulation. Inside HTS you have a lot of antennas (the phase array matrix to be exact) and based on phase difference for received wave between those antenna reception points, you calculate the bearing and elevation to emiter. The bearing and elevation calculation always have some error because of the electronics limitations, noise, reflected signals, Doppler effects and other signals in the air on the same band which you cannot completely filter out (to put it simply they add the phase noise to your measurement). So you have both, the exact one you asking for, but elevation error is much higher as its relative error to range is much higher. There are also much more reflection in elevation than there are in azimuth. Never the less, single measurement is not enough and it is like giving you generic area where the emiter is. This is how RWR work and where it's functionality ends. It simply display you the bearing and for elevation it can tell higher or lower than your plane as this is max of it's precision. If you want to learn more how old EWR works here is a nice video The RWR is simply phase detector where front and rear antennas are one axis, and left wing and right wing antena are another axis. Than (in case of early RWR) those phases were plotted on a scope and give you the visualization of a bearing. There is no way you get elevation other than leaning on a wing (antennas are directional) so you will se if signal will decay. Going back to HTS. At this point you need to think you have single 3D vector to emiter as HTS has this matrix phase array (which has hundreds of antennas in it). The error for it's measurements (where you project a cone from vector and error) give you 5nm flat space at 30-40 nm of distance (more or less). So now you should figure out why we have PGM levels! The longer you fly, and the greater the angular distance from all the measured 3D vectors you acquire, the more precise the location will be. This is basic method for decreasing error came from measurement theory. The error of the measurement can be decreased if you have a lot of them. And even more, in scope of triangulation, the bigger the difference in aspect to the measured location, the smaller the error of the projection cone will be. And this is how HTS is working. I do understand ESM system work by comparing phase different and resolve the angle from that. So it would need at least 2 antenna in any flat plane to resolved the direction However, recently, I was reading a paper released by LM, they said that their F-35 used an Azimuth only design (basically a linear horizontal array instead of a planar array), so it can only resolve target in azimuth and I find that to be a terrible decision, because by knowing elevation like the APR-47 on F-4G, you can measure the distance instantly in seconds Where as with azimuth only sensor, it is neccessary to fly for 30 seconds at the very least. So I just wonder the HTS is more similar to F-4 or F-35 system Link to comment Share on other sites More sharing options...
Rosly Posted January 6 Share Posted January 6 As electronic engineer I'm trying to point out that there is physics behind all technical solutions. You do not get infinite precision which you impose of having when making hopes for "instant measurement". Please refer to https://en.wikipedia.org/wiki/Accuracy_and_precision and https://en.wikipedia.org/wiki/Measurement_uncertainty In scope of phase measurements what you have is angles in one or two planes. The error of this measurement is huge (couple of degrees at least). You are not able to make instant projection of 3D vector over the surface from that and get precise location. RWR gives you very rough estimate of signal source azimuth. HTS is far more sophisticated and use triangulation and statistical methods to narrow down the position. There is nothing wrong in using single plane for measuring the direction for RWR. The design goals of this system if far different than those in HTS. The frequency range are different. The measurement time is different. The expected precision is different. And lastly I bet F-35 have far more superior sensors than original APR-47 Not mentioning F-35 work in network, because this network extend methods already used in HTS pod in block 52 of F-16, namely the TDOA. So comparing APR-47 to modern software define network sensors is just not sane Despite what some pilots say (like "Starbaby") the modern networked software defined radio system are far superior to any skilful pilot. But I get the point any story need at least 10 percent true If that wasn't the case, we would not get inch precision SAR images and still rely on vacuum display tubes and 2-plane phase differences. https://www.youtube.com/watch?v=RoZ_-6tvxu4 Link to comment Share on other sites More sharing options...
garrya Posted January 7 Author Share Posted January 7 19 hours ago, Rosly said: As electronic engineer I'm trying to point out that there is physics behind all technical solutions. You do not get infinite precision which you impose of having when making hopes for "instant measurement". Please refer to https://en.wikipedia.org/wiki/Accuracy_and_precision and https://en.wikipedia.org/wiki/Measurement_uncertainty In scope of phase measurements what you have is angles in one or two planes. The error of this measurement is huge (couple of degrees at least). You are not able to make instant projection of 3D vector over the surface from that and get precise location. RWR gives you very rough estimate of signal source azimuth. HTS is far more sophisticated and use triangulation and statistical methods to narrow down the position. There is nothing wrong in using single plane for measuring the direction for RWR. The design goals of this system if far different than those in HTS. The frequency range are different. The measurement time is different. The expected precision is different. And lastly I bet F-35 have far more superior sensors than original APR-47 Not mentioning F-35 work in network, because this network extend methods already used in HTS pod in block 52 of F-16, namely the TDOA. So comparing APR-47 to modern software define network sensors is just not sane Despite what some pilots say (like "Starbaby") the modern networked software defined radio system are far superior to any skilful pilot. But I get the point any story need at least 10 percent true If that wasn't the case, we would not get inch precision SAR images and still rely on vacuum display tubes and 2-plane phase differences. https://www.youtube.com/watch?v=RoZ_-6tvxu4 I understand that ESM/ELINT measurement are not supposed to be absolute accurate, but I find them somewhat similar to a radar, the angular accuracy of radar is also depend on their beamwidth which is often 2-3 degrees for fighter radars. (Of course radar get range measurement instantly unlike ESM/ELINT system) I get that multiple F-16 can be linked together and measure distance to target very quickly thanks to TDOA. But I’m more curious about single ship geolocation because apparently, according to pilot, a single F-35 can geolocate target quicker and more accurate than 3 F-16 Link to comment Share on other sites More sharing options...
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