Suppose my ULA(Uniform Linear Array) is along x-axis only, then definitely we can estimate elevation angle with this ULA. But if we lift this array from x-axis and place it along y-axis, then which angle can we estimate now with this array? I think in that case, we can estimate azimuth angle instead of elevation angle. Am I right? Please guide me in this regard.
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$\begingroup$ Are you working in 3 dimensions? The conventional definitions of terms like "azimuth" and "elevation" become somewhat murky in 3D. And it's usually best to describe the "pose" of your sensor array in terms of principled Euler rotations. In general though, a linear sensor array will measure the angle between its principle axis (the line it lies along) the signal direction of arrival. $\endgroup$– zcsttnJul 28, 2022 at 13:58
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$\begingroup$ No, I work in only 1 dimension. I just want to know that if with 2D array, we can estimate both the angles and with 1D array we can estimate only one angle, and if that one angle is elevation angle with 1D array along x-axis, then if we lift that 1D array from x-axis and place it along y-axis, then which angle can we estimate now? Whether it is still elevation angle or now its azimuth angle? $\endgroup$– matlabbeginnerJul 28, 2022 at 14:13
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1$\begingroup$ "ULA" can mean a lot of different thigs. Even when you expect your audience to know, it's a good idea to introduce a Three Letter Abbreviation (TLA) as spelled-out text, followed by the abbreviation in parentheses. Feel free to edit your question with this clarification. While you're at it, give an outline of what you're trying to do with it. $\endgroup$– TimWescottJul 28, 2022 at 15:34
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$\begingroup$ If you're restricting yourself to the x-y plane, and you have a linear array, there may not be much of a point in distinguishing between azimuth and elevation since all angular distances are defined in the x-y plane. If your array lies along the x axis, it will read the y-axis as the 0 angle. And if it lies along the y-axis, it will read the x-axis as the 0 angle. $\endgroup$– zcsttnJul 28, 2022 at 16:30
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$\begingroup$ But with 2D array (some antennas placed along x-axis and some antennas placed along y-axis and one antenna is at origin), we can estimate both the angles i.e., elevation as well as azimuth angles. And with 1D array i.e., antennas placed along x-axis, we can estimate elevation angle only. So my confusion is that when we can estimate both the angles with 2D array (1L), then if I place 1D array along x-axis and estimate elevation angle. Then if I lift that array from x-axis and place it along y-axis, then will I now be able to estimate the azimuth angle.? $\endgroup$– matlabbeginnerJul 28, 2022 at 16:44
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2 Answers
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I think I understand your question better now after talking in the comments. It seems you are "working in 3 dimensions", just restricting your sensor arrays to the x-y plane. That is, you're considering source directions that have some "z" component.
To answer your question: you will get more information if you measure with the ULA along the x-axis and then measure again with it along the y-axis. However, combining the results will not give you a single direction in "azimuth-elevation" angles. This is because a linear array only measures the "cone angle" around itself. So when you do as you describe, you'll end up with a cone around the x-axis and a cone around the y-axis, and their intersection will indicate possible source directions.
In order to narrow it down to a particular "azimuth-elevation" direction, you'd need to use a full 2-D grid as your sensor array.
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$\begingroup$ Still I am not getting you. What do you mean by cone angle? i.e., this cone angle is which one? Is it elevation when array is placed along x-axis and azimuth when array place along y-axis? Make me understand in simple words as I am not so expert. As I have asked: (1) ULA along x-axis can estimate elevation angle for us, so (2) if we place the same array along y-axis, will it estimate azimuth angle now? Or still it will be elevation angle only? $\endgroup$ Jul 28, 2022 at 17:22
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$\begingroup$ dear zcsttn and TimWescott ! Why are you silent? Am I asking some wrong question? Please guide me. $\endgroup$ Jul 29, 2022 at 12:50
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$\begingroup$ zcsttn, you're assuming a particular array coordinate system. We need @matlabbeginner to tell us which way his $x$ and $y$ axes are pointing before we can say which allows him to measure azimuth and elevation angles. $\endgroup$ Aug 27, 2022 at 18:26
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You are assuming a particular array coordinate system. We need to know which way the $x$ and $y$ axes point. The ULA will be able to measure angles in whatever dimension it exists.
So for example, if the ULA is along the $x$ axis, and the $x$ axis is vertical, it will be able to measure elevation angle. If the array is horizontal, it will be able to measure azimuth angles. I'm of course assuming common definitions of elevation and azimuth as vertical and horizontal angles, respectively.
If you want to measure angle of arrival (AoA) in 2 dimensions, you'll need a 2D array.
