Talk:Beamforming

Acoustic vs EM
I believe the statement regarding the difference between beamforming in the acoustic world versus the EM world is in error. In particular: "Sonar also differs from radar in that all directions can be listened and in theory broadcast to simultaneously and the phases manipulated entirely by signal processing software, as compared to present radar systems that use hardware to 'listen' in a single direction at a time."

WHile the whirling radar dish appears ubiquitous, phased array processing is becomming more popular in radar and communication RF sensors, particularly in defense systems.

http://www.nssl.noaa.gov/rrdd/par/index.shtml http://www.fas.org/man/dod-101/sys/ship/weaps/an-spy-1.htm http://www.fas.org/nuke/guide/china/facility/lpar.htm

These are not processed in baseband (as sonar is typically), but first converted to a more reasonable IF band (this conversion plays a little havoc with the phases, but in reality the signal processing ends up being the same as for acoustics). For instance, a radar system working around 10GHz, might down convert to 30MHz center frequency with a 20 MHZ bandwidth before using a bank of FPGA's to do the beamforming using phase interferometry. But I like that you've lead off with sonar systems/acoustics. I believe beamforming would be much easier to understand starting from this perspective.

I think the intent of that sentence was something like: But now that FPGAs are fast enough to handle radar data in real-time, and can be quickly re-programmed like software, the difference is blurring. --DavidCary 05:26, 15 October 2005 (UTC)
 * Sonar phased array has a data rate slow enough that it can be processed in real-time in software, which is flexible enough to transmit and/or recieve in several directions at once.
 * Radar phased array has a data rate so fast that it requires dedicated hardware processing, which is hard-wired to transmit and/or recieve in only one direction at a time.

Human brain
The article currently says

... At a certain level the human brain does the same thing, using signal processing on its 2 dimensional array (ears) to figure out where sound comes from.
 * 1 dimensional arrays are usually towed behind ships.
 * 2 dimensional arrays are common in side-scan sonar.
 * 3 dimensional arrays are used in 'sonar domes' in the modern submarine.

''This seems wrong to me. The sensors on a sonar dome cover just the outside 2 dimensional surface of the dome -- they don't fill up the entire 3 dimensional volume of the dome, do they ?'' And to call 2 ears a "2 dimensional array" seems a bit off. --DavidCary 05:26, 15 October 2005 (UTC)

Definition
The article one started with:


 * Beamforming is the process of delaying the outputs of the sensors in an array's aperture and adding these together, to reinforce the signal with respect to noise or waves propagating in different directions.

If I didn't already know what beam forming was about, this would make no sense. I tried to write a definition that was easier to understand, but now I think it is far too wordy.

--DavidCary 05:26, 15 October 2005 (UTC)

Agreed - it's too chatty. I don't really have the time/energy to rework however. Good luck :) Megapixie 06:21, 15 October 2005 (UTC)

I agree that it could use some tightening up. But as you can see from my recent edits, I'd rather have a "chatty" article than an incomprehensible one. (See Make technical articles accessible). --DavidCary 23:43, 2 December 2005 (UTC)

Explain better
The article says: "[The] signal-to-noise ratio of a beamformer with L antennas receiving a signal of power P is $$\frac{P\cdot L}{\sigma_n^2}$$." but does not specify the meaning of $$\sigma_n^2$$. Can anyone clarify? Laschatzer 14:17, 9 May 2007 (UTC)


 * The formula I mentioned above has not been further explained in the mean time. Should noone add an explanation anytime soon, I think it would be better to delete this formula. As it now stands, it conveys no useful information. Laschatzer (talk) 20:40, 15 April 2008 (UTC)
 * I have deleted the formula in question. Laschatzer (talk) 06:36, 25 April 2008 (UTC)

$$\sigma_n^2$$ is the thermal noise level and it actually made sense - you boost the signal $$ {L} $$ times but not the noise.

image
The image currently included in this article is not very enlightening. I understand basic beamforming, but I don't have any idea what that image is trying to show.

The image attempts to illustrate several things, but the only one I can identify is "beamforming" thanks to the caption - and I still don't see how it is illustrating beamforming. Yes there are multiple antennas which (I assume) are generating the radiation pattern, but HOW?

As for the other objects in the image, why are they there and what are they doing?
 * Is the blue thing a radiation pattern? If not, then what is it and why is it there? If so, then why is the main beam not pointed at the "desired user", and the null not pointed at the "interfering user"?
 * What is the green region? A radiation pattern would typically be shown on a circle or semicircle centered on the array, not a circle tangent to the array. Is it supposed to represent a dipole element factor? That should be left out of the image entirely, if it isn't explained at all.
 * Why does the "desired user" appear to be transmitting data to the "channel estimator" (?) which does not have antennas, rather than the "B/F" which does have antennas? —Preceding unsigned comment added by 146.6.205.120 (talk) 20:18, 16 April 2010 (UTC)

Casual bystander: I have to agree. The figure is less than clear. Is there nulling on an interferer going on? The black ray seemingly diffracted to the top left is especially baffling. —Preceding unsigned comment added by 131.203.13.81 (talk) 00:38, 20 May 2011 (UTC)

I agree. I removed it. 184.59.27.191 (talk) 01:13, 13 September 2018 (UTC)

Sensor Delay Line
I'm seeing references a beamforming approach called "Sensor Delay Lines ", that seem to be distinguished from tapped delay lines (delay and sum). Can anyone update the article to cover this? Burt Harris (talk) 01:22, 9 March 2016 (UTC)

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