Talk:Phased array

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I am doing a project on phased arrays, can anyone give me information? Thanks in advance. - john777

Contents 1 sonogram 2 Efficiency 3 SPY-1 4 Other Types of Energy and Send versus Receive 5 No derrivation on diffraction page 6 Math error? 7 Was there an earlier attempt at a phased array? 8 Very Large Array

[edit] sonogram

What about phased arrays for sonography? --Gbleem 01:37, 22 November 2005 (UTC)

[edit] Efficiency

How efficient are phased arrays (especially radars), compared with traditional radar dishes? i.e. how many watts consumes a phased array radar which radiates 1MW, and how much consumes a traditional one? Gorbalad 15:44, 2 December 2005 (UTC)

I fear that you will need to define your parameters more precisely. For instance, a typical antenna must be rotated to focus the main lobe on its target. Phased arrays have no need of such rotation up to +-90degrees. Second, how big/far away/fast is your target? Last, because phased arrays can re-direct radiation by merely shifting phased on relative antennae, they are indispensible for tracking multiple objects.

The short answer would be that a phased array with a minimum of 5 antennae is significantly more efficient than a single, unidirectional antenna. S.N. Hillbrand 14:24, 4 December 2005 (UTC)

thank you, but what i wanted to know was how much of the electrical power you put into a radar is effectively radiated? i.e. i wanted a comparison of the energy efficiency of both types. Gorbalad 22:09, 5 December 2005 (UTC)

Taking into account this clarification, there is no substantive difference between a phased array and a traditional radar. Both are simply antennae and their efficiency is a matter of product design, cabling, materials and the frequency at which you are operating. S.N. Hillbrand 12:28, 6 December 2005 (UTC)

The short-short answer is that all of the RF is radiated in some direction by any antenna system, except that lost due to resistance in the antenna elements, including passive reflective elements. Therefore, a reflective dish actually introduces more loss than a phased array. Do not be misled by the term "destructive interference" -- energy is not destroyed -- it is redirected. Joe Shupienis 05:31, 23 December 2005 (UTC)

[edit] SPY-1

I've removed the remarks about controlling 100+ missiles. I'd like to see the citation for that, but I doubt that one exists. I also attempted to clarify missile guidance vs fire control. The paragraph probably needs more work, but I haven't the time to look for references right now. --Dual Freq 01:29, 12 April 2006 (UTC)

I've found a cite (german milatary) that explains the Aegis can track up to 100 targets at a time. I will update the content and add the reference.Logicnazi 08:40, 11 August 2006 (UTC)

That doesn't mean it can control 100+ missiles at a time. It means it can do all that stuff at the same time. NOAA has virtually the same sentence only they say track capacity not capability. This high powered Navy radar is able to perform search, track and missile guidance functions simultaneously with a track capacity of over 100 targets. Everything is a target to a radar, any search radar can probably track 100+ targets depending on how you define "track". Due to physics and timing it is impossible for it to control 100+ missiles in flight. Radar pulses take time to transmit and receive. Searching, detecting new targets, tracking existing tracks and guiding missiles take several pulses per second to do, there isn't enough time to do all that in one second and have 100 missiles in flight. On top of real targets, there are false targets like clutter, jamming, chaff all that stuff takes time for a computer to sort out. Even if it were possible, I believe there are only 4 SPG-62 directors on the ship and they are required for terminal guidance. Certainly 4 directors can't terminally guide 100+ missiles. SPY-1 does mid-course only, of course maybe that could change with technology. See also FAS SPY-1 weaknesses. Dual Freq 14:56, 11 August 2006 (UTC)

[edit] Other Types of Energy and Send versus Receive

(1) Phased arrays work with any type of wave energy. (2) The phased array concept works whether you are sending or receiving signals, i.e. even if you are only listening. (3) Search the Internet for "phased array microphone" to read about examples of acoustic receive-only mode. (4) Is 3-D seismic analysis of signals from an array of geophones a phased array application? (5) This is a good article on phased array radar. I'd like to see it expanded to include other wave energy and other applications. This is WAY out of my field (geology) and I don't feel competent to expand it. Rocky143 11:05, 1 December 2006 (UTC)

(4) Seismic analysis that uses continuous waves from a vibrator as source treats its array of geophones as a phased array. Other seismic explorations use an impulse source such as an explosion and here the geophone signals are combined with different delays to get a similar form of steerability. Note that it is not necessary for all the geophones of an array to be present at once: at sea it is common for a boat to tow a string of microphones whose detections of repeated explosions are recorded for combination later as a virtual or "synthetic" wide-area array.84.210.139.189 19:07, 13 January 2007 (UTC)cuddlyable3

[edit] No derrivation on diffraction page

This article states "We will begin from the N-slit diffraction pattern derived on the diffraction page." But there is no derrivation on that page - only a statement that a rigours matematical derrivation gives the equation shown. —The preceding unsigned comment was added by 213.78.42.15 (talk) 09:06, 26 April 2007 (UTC). If anyone can derrive the radiation pattern that is valid for arbitrary spacing and works for the near field too (i.e neglect the r squared and r cubed terms of E only at the last minute), I would be interested!

Yeah, the "Mathematical perspective and formulae" section needs to be cleaned up. Beyond referring to a non-existent derivation, there is no definition of symbols, and the small angle sine approximation is used with no justification I can see. If someone knows what's going on here, please edit. 130.216.54.198 (talk) 23:56, 30 March 2008 (UTC)

[edit] Math error?

Shouldn't the denominator in the first term be Sin[θ], instead of θ? Bswatson 23:54, 23 July 2007 (UTC)Brad

- Small angle approximation, presumably —Preceding unsigned comment added by 81.187.222.201 (talk) 09:50, 22 October 2007 (UTC)

[edit] Was there an earlier attempt at a phased array?

I was reading a Nobel lecture here. Look particularly at pages 239-240 (14-15 in the pdf). I know this was before radar, but doesn't this make it look like Braun in 1905 made the first successful attempt at phased array transmission? Phased array doesn't only refer to radar. Jonnyapple (talk) 19:32, 2 April 2008 (UTC)

[edit] Very Large Array

Would it be all right to add "see also: Very Large Array"? --Ancheta Wis (talk) 03:17, 22 April 2008 (UTC)