Editing Continuous-wave radar (section)

{{Short description|Type of radar where a known stable frequency continuous wave radio energy is transmitted}}
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| image = Cw radar.png
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{{Annotation|3|63|[[Transmitter]]|font-weight=bold|font-size=12}}
{{Annotation|143|57|transmitted<br />energy|font-weight=bold|text-align=center|color=white|font-size=14}}
{{Annotation|13|113|[[Receiver (radio)|Receiver]]|font-weight=bold|font-size=12}}
{{Annotation|173|113|backscattered energy,<br />containing much information<br />about the backscatterer}}
| caption = Principle of a measurement with a continuous-wave radar
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'''Continuous-wave radar''' ('''CW radar''') is a type of [[radar]] system where a known stable frequency [[continuous wave]] [[radio]] energy is transmitted and then received from any reflecting objects.<ref>{{cite web|url=http://www.fas.org/man/dod-101/navy/docs/es310/cwradar/cwradar.htm|title=Continuous-wave Radar|publisher=Federation of American Scientists}}</ref> Individual objects can be detected using the [[Doppler radar|Doppler effect]], which causes the received signal to have a different frequency from the transmitted signal, allowing it to be detected by filtering out the transmitted frequency.

Doppler-analysis of radar returns can allow the filtering out of slow or non-moving objects, thus offering immunity to interference from large stationary objects and slow-moving [[Clutter (radar)|clutter]].<ref>{{cite journal| last1=Srivastav| first1=A.| last2=Nguyen| first2=P.| last3=McConnell| first3=M.| last4=Loparo| first4=K. N.| last5=Mandal| first5=S.| title=A Highly Digital Multiantenna Ground-Penetrating Radar System| journal=IEEE Transactions on Instrumentation and Measurement| volume=69| pages=7422–7436| date=October 2020| doi=10.1109/TIM.2020.2984415| s2cid=216338273| url=https://doi.org/10.1109/TIM.2020.2984415| url-access=subscription}}</ref><ref>{{cite web|url=http://www.radartutorial.eu/02.basics/Continuous%20Wave%20Radar.en.html| title=Continuous-wave Radar|publisher=Radartutorial.eu}}</ref> This makes it particularly useful for looking for objects against a background reflector, for instance, allowing a high-flying aircraft to look for aircraft flying at low altitudes against the background of the surface. Because the very strong reflection off the surface can be filtered out, the much smaller reflection from a target can still be seen.

CW radar systems are used at both ends of the range spectrum.
* Inexpensive radio-altimeters, proximity sensors and sports accessories that operate from a few dozen feet to several kilometres
* Costly [[early-warning radar|early-warning]] CW angle track (CWAT) radar operating beyond 100&nbsp;km for use with surface-to-air missile systems