Talk:Doppler radar

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In the first paragraph under "Basic concept", shouldn't there be a "not" in the statement "Since the system could broadcast and receive at the same time"? --Brouhaha 18:50, 4 Mar 2005 (UTC)

Contents

[edit] Velocity image?

Shouldn't the example radar image be velocity and not reflectivity, since this is the Doppler radar article? Ardric47 01:58, 19 April 2006 (UTC)

Agree...will add it. -Runningonbrains 23:50, 1 September 2006 (UTC)

[edit] Usage

Does anyone know when it first came into use by weather stations? --132.170.47.159 00:11, 29 August 2006 (UTC)

[edit] Merge Pulse-Doppler radar Here

While pulse Doppler radar works on phase shift an CW/FM work Doppler effect, both type of radars are called Doppler. Therefore it would be best to merge both article into this one and explain completely the concepts. Pierre cb 14:04, 4 November 2006 (UTC)

That might be a major undertaking, as each subject hasn't changed much in a year due to the daunting task of putting it all in eighth-grade English. 137.240.136.82 17:50, 5 December 2006 (UTC)

It is important that there is a distinction made between weather radar and "normal" radar. When searching for radar information Wikipedia doesn't make that distinction, yet while they work on the same principles they are distinctly different

There is a Weather radar article that is independant of the two articles to merge and explain the use of pulse-pair to extract velocity data. Pulse-Doppler radar and Doppler radar articles are not about weather but just the principle of using radar to record the velocities of targets two different ways (the first one used by weather radars). Using the name of Doppler radar for weather radar is an American misnomer as this type of weather radar was introduce by the National Weather Service and the confusion popularized by television stations. Wikipedia should stop this confusion. Pierre cb 18:33, 6 December 2006 (UTC)

I don't believe that merging this Topic with Pulse-Doppler radar is helpful. Although both use the Doppler principle, the two systems are totally different. The most common use of PD Radar is in attack radars for military aircraft, and these systems utilise a number of other phenomena in order to work, such as coherency, pulse profiling etc (I can't comment on its use in weather radar, because I have no experience of these systems). Doppler radar techniques are most often found in ground speed computational systems, such as might be found as part of a navigation system, or as a hover aid in helicopters. The applications are sufficiently diverse to warrant two entries, although the linkage between them is relevant. User:TJC

Since there seems to be no dissent, I'll remove the merge proposal sometime during the weekend.--Terry C 13:26, 12 January 2007 (UTC)

[edit] Direction-sensing Doppler Radar

A simple Doppler radar gives an output (typically audio) frequency proportional to the component of velocity of the target in the direction parallel to the radar beam. However it cannot distinguish between motion towards the radar unit and away from it. More recent traffic-speed radars (and police radar guns) can distinguish directionality, and appear to do so using a pair of mixer diodes arranged to have quadrature (relative) phase shift. This can be expected to yeild a pair of baseband outputs with relative phase advance/retarded dependent on the towards/away direction of the target. Further Digital Signal Processing techniques including Fast Fourier Transform are used on the baseband output to help identify a multiplicity of targets and extract fastest/strongest etc. See for example this patent:

http://www.patentstorm.us/patents/7068212-claims.html

It would be nice to add a paragraph or two on this technique to the Wikipedia Doppler Radar article as the technique is both technically rather neat, and the application can be observed in real-world traffic speed indicators. 80.42.242.203 22:17, 17 March 2007 (UTC) Andrew Steer www.techmind.org

[edit] Not detected at all?

If non-moving objects can not be detected by Doppler radars then how come the weather radars detect ground echoes? Assuming I'm right, the following needs re-writing:

"A target with no range-rate reflects a frequency near the transmitter frequency, and cannot be detected. The classic zero doppler target is one which is on a heading that is tangential to the radar antenna beam. Basically, any target that is heading 90 degrees in relation to the antenna beam cannot be detected." --Weedrat (talk) 11:23, 20 April 2008 (UTC)