RF communication through steel

• Nov 30, 2005

• #2

VEBill

Military

Apr 25, 2002

7,090

Most airplanes are made of aluminum, not steel. Based on past experience, I'm sure you be back with addditional information to correct my misunderstanding of what you have written...

The signal does not have to pass directly through the direct straight line. Diffraction and reflections will occur around the object blocking the Line Of Sight path. This diffraction can be modelled using GTD/UTD (Google those terms) - but it gets complicated.

If the frequency is sufficiently low, the RF wouldn't even 'notice' the 'small' object.

 

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• Nov 30, 2005

• #3

BrianG

Military

Aug 28, 2001

357

WOW! Do you really mean through steel? (a steel aeroplane!!) The basic answer will be very low/zero range, but frequency details are needed to give possible power figures.
Why will the signal not pass around the fuselage? Unless your aeroplane fuselage is a solid cylinder or unmanned such as a UAV, some of the signal will pass through any windows or cockpit canopy (think using a mobile phone inside a car - sufficient signal goes through the windows to reach the base station)

 

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• Nov 30, 2005

• #4

IRstuff

Aerospace

Jun 3, 2002

44,447

Cell phones work perfectly fine on airplanes as well.

TTFN

 

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• Nov 30, 2005

• #5

VisiGoth

Electrical

Jul 20, 2005

260

Does your "airplane" have a leaky antenna coupler connecting the inside of the pressure vessel with the outside of the pressure vessel? If it does, it may be designed for cell phone bands or a specific range of frequency. These are also used inside train tunnels, so you get much better performance than theory would show without the leaky antenna.

 

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• Nov 30, 2005

• Thread starter
• #6

pacej51

Electrical

Jul 15, 2005

4

Thanks for the responses. It sounds like the signal from device 1 would eventually reach device 2, albeit with some diffraction.

I am interested in the time of flight of the signal. If there is signifigant diffraction, this will distort this measurement.

I am not sure what frequency we will be using, but from everything I've read it seems that lower is better. I'd say a good guess is that we'd use something in the 30 MHz range.

That said, if time of flight is my main concern I guess it makes more sense to have enough devices where at least one line of sight connection is possible.

Does this make sense?

 

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• Nov 30, 2005

• #7

itsmoked

Electrical

Feb 18, 2005

19,114

Multiple devices have their own problems too.

 

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• Nov 30, 2005

• #8

IRstuff

Aerospace

Jun 3, 2002

44,447

TOF for 400 ft --> 3.7 ns

30 MHz --> 33 ns period

TTFN

 

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• Nov 30, 2005

• #9

zeitghost

Computer

Oct 8, 2003

400

According to a tv documentary I just watched some of the early supersonic aircraft were made of stainless steel because they got too hot to use aluminium.

 

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• Dec 1, 2005

• #10

VEBill

Military

Apr 25, 2002

7,090

"TOF for 400 ft --> 3.7 ns"

Hmmm... ...am I missing something?

 

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• Dec 1, 2005

• #11

IRstuff

Aerospace

Jun 3, 2002

44,447

sorry, should have been 37.5 ns.

TTFN

 

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• Dec 1, 2005

• #12

VEBill

Military

Apr 25, 2002

7,090

"400 feet divided by 299792458 meters per second in nanoseconds"

Precanned Google Calculator link:

http://tinyurl.com/9zyl4

406.681345 nanoseconds

 

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• Dec 1, 2005

• #13

IRstuff

Aerospace

Jun 3, 2002

44,447

me bad

TTFN

 

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