L
Leo Baumann
Guest
Hi
www.leobaumann.de/ReflexENG.pdf
Regards Leo
www.leobaumann.de/ReflexENG.pdf
Regards Leo
Guest
On Sunday, May 19, 2019 at 12:30:20 AM UTC-4, Leo Baumann wrote:
That paper has little to do with stealth. EM field intensity may decrease as 1/r due to atmospheric loss, but you neglect the fact that real signals are propagated by antennae with finite aperture with finite solid angle. This means the power intercepted by the target, for purposes of reflection, is in the ratio of the target area to the area subtended by the solid angle, which degrades by 1/r^2, a very large loss.
Stealth is all about geometrical design to reduce reflection/eliminate resonators:
https://en.wikipedia.org/wiki/Stealth_technology
That paper has little to do with stealth. EM field intensity may decrease as 1/r due to atmospheric loss, but you neglect the fact that real signals are propagated by antennae with finite aperture with finite solid angle. This means the power intercepted by the target, for purposes of reflection, is in the ratio of the target area to the area subtended by the solid angle, which degrades by 1/r^2, a very large loss.
Stealth is all about geometrical design to reduce reflection/eliminate resonators:
https://en.wikipedia.org/wiki/Stealth_technology
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Leo Baumann
Guest
Am 20.05.2019 um 00:22 schrieb bloggs.fredbloggs.fred@gmail.com:
The basis of STEALTH is a total reflection by appropriate means, such as
special paint coating, to attenuate 6 dB, which is physically achievable.
The basis of STEALTH is a total reflection by appropriate means, such as
special paint coating, to attenuate 6 dB, which is physically achievable.
L
Leo Baumann
Guest
Am 20.05.2019 um 01:11 schrieb Winfield Hill:
> 6 dB is nothing.
1/2, the only physically possible by coating ...
> 6 dB is nothing.
1/2, the only physically possible by coating ...
W
Winfield Hill
Guest
Leo Baumann wrote...
6 dB is nothing.
--
Thanks,
- Win
6 dB is nothing.
--
Thanks,
- Win
Guest
On Sunday, May 19, 2019 at 6:40:50 PM UTC-4, Leo Baumann wrote:
Read the wiki article. There's a history there. No one started out by looking at paint schemes.
Read the wiki article. There's a history there. No one started out by looking at paint schemes.
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Leo Baumann
Guest
Am 20.05.2019 um 01:11 schrieb Winfield Hill:
> 6 dB is nothing.
6 dB attenuation electric field
3 dB attenuation power
> 6 dB is nothing.
6 dB attenuation electric field
3 dB attenuation power
J
Jasen Betts
Guest
On 2019-05-19, Winfield Hill <hill@rowland.harvard.edu> wrote:
I'm guessing that if your coating has a resistance of 300 ohms per
square (or some other magic number) performance is significantly
better, it's a matter of making the coating black to radar frequencies.
--
When I tried casting out nines I made a hash of it.
I'm guessing that if your coating has a resistance of 300 ohms per
square (or some other magic number) performance is significantly
better, it's a matter of making the coating black to radar frequencies.
--
When I tried casting out nines I made a hash of it.
Guest
On Sunday, May 19, 2019 at 6:40:50 PM UTC-4, Leo Baumann wrote:
This fall into the category of RAM, and it's not easy to do. Major limitations to effectiveness are bandwidth and angle of impingement dependency. And this is not cheap. Looks like it's mainly used to augment the geometric shaping of the airframe to further reduce reflection from those areas known to be vulnerable.
One summary:
"Essentially, RAM absorbs the incident EM energy and converts it into heat, thereby reducing
the scattered energy towards the radar. RAM is known to be quite effective in controlling the
backscattering than forward scattering (Hiatt et al. 1960). RAMs have relatively high values of
imaginary part of permittivity and permeability. Such coatings result in change in polarisation
of the scattered waves.
Narrowband RAM coatings, such as the Salisbury screen and Dallenbach layer, have been
used since 1950s. However, modern radar systems span a wide range of frequency. Hence, the
need for wideband RAMs is apparent. A typical RAM employed on aircraft could be a ferritebased paint or a composite. However, there are significant implications of using RAM. Firstly,
most of them are toxic. Secondly, RAM coatings require precise application techniques, as the
coating thickness and smoothness must be uniform across the platform.
Ideally a RAM should not impose weight penalty due to speed and pay load considerations.
It should possess high mechanical strength and should be anticorrosive, chemically stable and
should not get charged at high temperature. It must have a wideband RCSR. Lastly, it should
be effective in all directions (Vinoy and Jha 1996). The RAM application process typically
involves robotic sprayers that can accurately control the coating thickness.. Furthermore, these
coatings require strict constitutive parameter tolerances as well as uniformity in order to achieve
the desired result. Therefore, the cost of implementation of RAM is often too high. Another
issue is that RAM also increases the weight of the platform. This may have notable impact on
the vehicle performance aerodynamically.
For different platforms, RAM coatings have been developed with appropriate combination
of rubber, cotton-glass, epoxy and mica. Other possibilities are graphite fibres, Kevlar and
ferrites. The materials can be of different forms such as sheets, honeycombs, laminates, etc.
Ferrite materials in forms of flakes, wires or microspheres can be loaded into glassâepoxy or
silicon rubber. The inks and coatings can be applied on kapton film or epoxy honeycombs.
Radar-absorbing paints are also coated over the surface of the vehicles. These paints consist
of small ferrite particles that are polarised towards the impinging wave. Such paints are
prepared by mixing solid iron oxides with various polymer resins, such as epoxy and plastics.
The constitutive parameters including thickness of the paint, fix the resonance frequency for
maximum absorption. "
This fall into the category of RAM, and it's not easy to do. Major limitations to effectiveness are bandwidth and angle of impingement dependency. And this is not cheap. Looks like it's mainly used to augment the geometric shaping of the airframe to further reduce reflection from those areas known to be vulnerable.
One summary:
"Essentially, RAM absorbs the incident EM energy and converts it into heat, thereby reducing
the scattered energy towards the radar. RAM is known to be quite effective in controlling the
backscattering than forward scattering (Hiatt et al. 1960). RAMs have relatively high values of
imaginary part of permittivity and permeability. Such coatings result in change in polarisation
of the scattered waves.
Narrowband RAM coatings, such as the Salisbury screen and Dallenbach layer, have been
used since 1950s. However, modern radar systems span a wide range of frequency. Hence, the
need for wideband RAMs is apparent. A typical RAM employed on aircraft could be a ferritebased paint or a composite. However, there are significant implications of using RAM. Firstly,
most of them are toxic. Secondly, RAM coatings require precise application techniques, as the
coating thickness and smoothness must be uniform across the platform.
Ideally a RAM should not impose weight penalty due to speed and pay load considerations.
It should possess high mechanical strength and should be anticorrosive, chemically stable and
should not get charged at high temperature. It must have a wideband RCSR. Lastly, it should
be effective in all directions (Vinoy and Jha 1996). The RAM application process typically
involves robotic sprayers that can accurately control the coating thickness.. Furthermore, these
coatings require strict constitutive parameter tolerances as well as uniformity in order to achieve
the desired result. Therefore, the cost of implementation of RAM is often too high. Another
issue is that RAM also increases the weight of the platform. This may have notable impact on
the vehicle performance aerodynamically.
For different platforms, RAM coatings have been developed with appropriate combination
of rubber, cotton-glass, epoxy and mica. Other possibilities are graphite fibres, Kevlar and
ferrites. The materials can be of different forms such as sheets, honeycombs, laminates, etc.
Ferrite materials in forms of flakes, wires or microspheres can be loaded into glassâepoxy or
silicon rubber. The inks and coatings can be applied on kapton film or epoxy honeycombs.
Radar-absorbing paints are also coated over the surface of the vehicles. These paints consist
of small ferrite particles that are polarised towards the impinging wave. Such paints are
prepared by mixing solid iron oxides with various polymer resins, such as epoxy and plastics.
The constitutive parameters including thickness of the paint, fix the resonance frequency for
maximum absorption. "
L
Leo Baumann
Guest
Am 20.05.2019 um 15:09 schrieb bloggs.fredbloggs.fred@gmail.com:
There is only a minimum thickness of the color. The parameters are
determined by the cut-off frequency, the conductivity and the relative
dielectricity (see paper).
There is only a minimum thickness of the color. The parameters are
determined by the cut-off frequency, the conductivity and the relative
dielectricity (see paper).
Guest
On Sunday, May 19, 2019 at 10:21:19 PM UTC-4, Leo Baumann wrote:
That's a common misperception, but dB attenuation in power and intensity are one and the same number. If you have a quantity X for which the power is proportional to X^2 then 20LOG(X)= 10LOG(X^2) or dB(intensity)=dB(power).
That's a common misperception, but dB attenuation in power and intensity are one and the same number. If you have a quantity X for which the power is proportional to X^2 then 20LOG(X)= 10LOG(X^2) or dB(intensity)=dB(power).
P
Phil Hobbs
Guest
On 5/20/19 11:23 AM, Leo Baumann wrote:
Decibels are always logarithms of power ratios.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.net
http://hobbs-eo.com
Decibels are always logarithms of power ratios.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.net
http://hobbs-eo.com
L
Leo Baumann
Guest
Am 20.05.2019 um 16:31 schrieb bloggs.fredbloggs.fred@gmail.com:
> That's a common misperception, but dB attenuation in power and intensity are one and the same number. If you have a quantity X for which the power is proportional to X^2 then 20LOG(X)= 10LOG(X^2) or dB(intensity)=dB(power).
http://www.sengpielaudio.com/Rechner-verstaerkung.htm
> That's a common misperception, but dB attenuation in power and intensity are one and the same number. If you have a quantity X for which the power is proportional to X^2 then 20LOG(X)= 10LOG(X^2) or dB(intensity)=dB(power).
http://www.sengpielaudio.com/Rechner-verstaerkung.htm
L
Leo Baumann
Guest
Am 20.05.2019 um 16:31 schrieb bloggs.fredbloggs.fred@gmail.com:
> That's a common misperception, but dB attenuation in power and intensity are one and the same number. If you have a quantity X for which the power is proportional to X^2 then 20LOG(X)= 10LOG(X^2) or dB(intensity)=dB(power).
no
Power reflection attentuation is 10LOG(P2=1/P1=2)=-3.01 dB
electric field attenuation is 20LOG(E2/E1)=-6.02 dB
> That's a common misperception, but dB attenuation in power and intensity are one and the same number. If you have a quantity X for which the power is proportional to X^2 then 20LOG(X)= 10LOG(X^2) or dB(intensity)=dB(power).
no
Power reflection attentuation is 10LOG(P2=1/P1=2)=-3.01 dB
electric field attenuation is 20LOG(E2/E1)=-6.02 dB
L
Leo Baumann
Guest
Am 20.05.2019 um 16:31 schrieb bloggs.fredbloggs.fred@gmail.com:
> That's a common misperception, but dB attenuation in power and intensity are one and the same number. If you have a quantity X for which the power is proportional to X^2 then 20LOG(X)= 10LOG(X^2) or dB(intensity)=dB(power).
.... but I know what You mean
> That's a common misperception, but dB attenuation in power and intensity are one and the same number. If you have a quantity X for which the power is proportional to X^2 then 20LOG(X)= 10LOG(X^2) or dB(intensity)=dB(power).
.... but I know what You mean
L
Leo Baumann
Guest
Am 20.05.2019 um 17:47 schrieb bloggs.fredbloggs.fred@gmail.com:
I know what You mean. I made a mistake in E, H and Power.
It is 10LOG(P2/P1)=10LOG(1/2)=-3.01 dB
I know what You mean. I made a mistake in E, H and Power.
It is 10LOG(P2/P1)=10LOG(1/2)=-3.01 dB
Guest
On Monday, May 20, 2019 at 11:23:24 AM UTC-4, Leo Baumann wrote:
Did you miss the part about P ~ E^2 ???
http://farside.ph.utexas.edu/teaching/302l/lectures/node119.html
Your answers to the comments explain a lot.
Did you miss the part about P ~ E^2 ???
http://farside.ph.utexas.edu/teaching/302l/lectures/node119.html
Your answers to the comments explain a lot.