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AG Radar EXP1-EXP2-EXP3 submodes. Doppler Sharpening or Synthetic Aperture?


DmitriKozlowsky

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I noticed that when creating EXP radar maps , aircraft has to fly stable path, and expanded zoom radar picture is missing about 10 degree center cone of radar along boresight. I recall from past sim(Jane's F-15E), that high resolution SAR radar requires aircraft to fly stable path and speed for few seconds, and be about 10-15 degrees off nose boresight. 

Are F/A-18C AG radar EXP modes doppler beam sharpening or lower resolution SAR shots?

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They're Doppler Beam Sharpening, hence the DBS designation.

Looking through Chuck's Guide the black region seems to be a feature, as the Doppler shift is too great along the flight path. As you say, being slightly off boresight will allow an area to be mapped.

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32 minutes ago, HammerUK9 said:

They're Doppler Beam Sharpening, hence the DBS designation.

Looking through Chuck's Guide the black region seems to be a feature, as the Doppler shift is too great along the flight path. As you say, being slightly off boresight will allow an area to be mapped.

Center boresight blind spot is what made me think synthetic aperture. 

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Biggest practical difference with SAR in DCS is it's a constant 1.2x1.2nm area.

 

Exp1&2 are angle rate, so the amount of area covered will vary with distance.

 

This means within 7nm EXP2 actually produces a higher quality image than EXP3. Again, this is my experience with DCS.


Edited by LastRifleRound
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14 hours ago, DmitriKozlowsky said:

Center boresight blind spot is what made me think synthetic aperture. 

 

Doppler Beam Sharpening still requires a certain radial speed to resolve the distance, so both DBS and SAR (which uses DBS btw) have a dead zone in front of the aircraft.

 

See more info: https://www.radartutorial.eu/20.airborne/ab05.en.html

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  • 1 year later...
On 1/26/2021 at 8:54 AM, toilet2000 said:

 

Doppler Beam Sharpening still requires a certain radial speed to resolve the distance, so both DBS and SAR (which uses DBS btw) have a dead zone in front of the aircraft.

 

See more info: https://www.radartutorial.eu/20.airborne/ab05.en.html

Still shouldn't exist in the image as it would be filled in with MAP resolution data.

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Not quite how DBS works. The "dead spots" are due to a weak relationship between Doppler information and angle. "Cross range resolution" means resolution in the azimuthal direction. For a given Doppler color precision there is a certain range of azimuths which correspond. This window is narrowest at 45 degrees relative to the motion and vanishes to zero at 0 and 90. The sharpening is only occurring in the "beam width" dimension which is why the technique is called beam sharpening. Range resolution is unaffected plus anything that's moving over the ground gets sharpened the wrong way thus blurred.

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