Range aliasing: Difference between revisions

Latest revision as of 15:58, 20 February 2012

range aliasing[edit | edit source]

(Also called range folding.) In radar meteorology, a sampling problem that arises when echoes located beyond the maximum unambiguous range (r_max) are received as if they were within this range of the radar.

A radar ordinarily computes range to targets by measuring the time interval between the transmission of a pulse and the receipt of the returned signal, assuming that the signal was associated with the pulse just transmitted. However, depending on the pulse repetition frequency, the returned signal may be associated with one of several pulses transmitted prior to the latest one. Therefore, a returned signal, indicated as originating at range r, could have originated at r + r_max (second-trip echo), or r + 2r_max (third-trip echo), etc. A range-aliased echo from a weather target is sometimes recognizable by a distorted shape. It may appear elongated radially or shrunk in azimuth extent because the radial length is unaffected by aliasing and is a correct measure of the target size while the azimuthal width decreases with increasing range from the radar.

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-<div class="definition"><div class="short_definition">(<br/>''Also called'' range folding.) In [[radar meteorology]], a sampling problem that arises  when [[echoes]] located beyond the [[maximum unambiguous range]] (''r''<sub>max</sub>) are received as if they  were within this [[range]] of the [[radar]].</div><br/> <div class="paragraph">A radar ordinarily computes range to targets by measuring the time interval between the transmission  of a [[pulse]] and the receipt of the returned [[signal]], assuming that the signal was associated  with the pulse just transmitted. However, depending on the [[pulse repetition frequency]], the  returned signal may be associated with one of several pulses transmitted prior to the latest one.  Therefore, a returned signal, indicated as originating at range ''r'', could have originated at ''r'' + ''r''<sub>max</sub>  ([[second-trip echo]]), or ''r'' + 2''r''<sub>max</sub> (third-trip echo), etc. A range-aliased echo from a weather target  is sometimes recognizable by a distorted shape. It may appear elongated radially or shrunk in  [[azimuth]] extent because the radial length is unaffected by [[aliasing]] and is a correct measure of the  [[target]] size while the azimuthal width decreases with increasing range from the radar.</div><br/> </div>
+<div class="definition"><div class="short_definition">(''Also called'' range folding.) In [[radar meteorology]], a sampling problem that arises  when [[echoes]] located beyond the [[maximum unambiguous range]] (''r''<sub>max</sub>) are received as if they  were within this [[range]] of the [[radar]].</div><br/> <div class="paragraph">A radar ordinarily computes range to targets by measuring the time interval between the transmission  of a [[pulse]] and the receipt of the returned [[signal]], assuming that the signal was associated  with the pulse just transmitted. However, depending on the [[pulse repetition frequency]], the  returned signal may be associated with one of several pulses transmitted prior to the latest one.  Therefore, a returned signal, indicated as originating at range ''r'', could have originated at ''r'' + ''r''<sub>max</sub>  ([[second-trip echo]]), or ''r'' + 2''r''<sub>max</sub> (third-trip echo), etc. A range-aliased echo from a weather target  is sometimes recognizable by a distorted shape. It may appear elongated radially or shrunk in  [[azimuth]] extent because the radial length is unaffected by [[aliasing]] and is a correct measure of the  [[target]] size while the azimuthal width decreases with increasing range from the radar.</div><br/> </div>
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