What increases the penetration power of a signal: power or energy?

[MrOmnos]

If I want my signal to penetrate walls. Do I increase the power of the signal or do I use a high energy high frequency signal?

[tatus1969]

energy is power * time, so where's the difference? not clear what you mean.

[jeroen79]

What is, in your view, the difference between a high power signal and a high energy signal?
(Power is energy over time.)

[joseph nicholas]

The higher the frequency the shorter the electrical waves traveling through the air.  Thus, microwaves have a higher penetration factor through walls.  Take for example cell phone and wifi signals, relatively low power but microwave frequency, the same cannot be said for fm radio.  Low frequency, low power.  You need an external antenna to get most fm signals.

Hope this helps.

[snarkysparky]

higher frequencies are more attenuated when passing through materials.  However higher frequencies are better at finding ways around materials  (  cracks and small openings ).

So to penetrate walls use a lower frequency.

[rsjsouza]

Check the attached paper. It has some interesting data.

[Spuddevans]

Thus, microwaves have a higher penetration factor through walls.

I think that is not quite correct, the higher the frequency the lower they will penetrate through walls. An easy experiment is if you have a dual-band wifi access point, connect on 2.4ghz and move to where you have a few brick walls inbetween you and the access point and see what signal level you have. then switch to 5.4ghz and see if you can even connect at all, you will see that the 5.4ghz signal is much reduced in comparison with the 2.4ghz.

The shorter the wavelength, the more it is attenuated by physical objects, especially objects greater in size than the wavelength.

To the OP, it seems that your question needs clarification, in my mind energy is power. And a lot depends upon what you are trying to penetrate through, ie concrete walls, timber frame walls, open space, woodland, across water? Also frequency makes a great difference along with antenna type and height, 10watts at 14mhz could get you halfway around the world if the atmospheric conditions are good, whereas you could struggle to get 10 miles at 440mhz at 10 watts (depending on antenna type and height)

Tim

[Ian.M]

The higher the frequency the shorter the electrical waves traveling through the air.  Thus, microwaves have a higher penetration factor through walls.  Take for example cell phone and wifi signals, relatively low power but microwave frequency, the same cannot be said for fm radio.  Low frequency, low power.  You need an external antenna to get most fm signals.

Hope this helps.

On the contrary.  Masonry, non-reinforced concrete, wood and other common non-metallic building materials are virtually transparent to low frequency signals, (welded reinforcing mesh or foil backed insulation can act as a Faraday cage and block or substantially attenuate them) but as you increase the frequency the attenuation also increases and by the time you get up to GHz band frequencies the penetration is vastly reduced.  e.g. Ku band Satellite downlink signals are severely attenuated by a single layer of wet cloth e.g. a linen tea-towel and even the wrong type of paint on a satellite dish or a film of surface water due to rain, fog or dew causes noticeable attenuation.  As a rough rule of thumb, in an individual dwelling without large areas of metal in the structure, and without noise sources in the bands of interest, VHF band and below broadcast signals can be easily be received on an indoor antennae, UHF band can be problematic and an external antennae is usually recommended, and SHF upwards almost invariably requires an external directional antennae with line of sight to the transmitter.   Of course EIRP and range have a large influence on whether or not the signal level is usable after penetrating a wall, and its worth noting that 1W EIRP (FCC part 15 limit for video senders, WiFi etc.) at a range of tens of meters  is comparable to a 1MW TV transmitter at a range of tens of Km.

The problem with VHF FM radio is the large number of metal objects in the wall of a typical home with dimensions comparable to a wavelength.  Wiring, plumbing, plaster reinforcing mesh on corners etc. This creates a complex self-interference pattern and moving the antennae distances of the order of half a wavelength to find a local maxima or a larger distance to get out of the shadow of a larger area of metal is commonly necessary to obtain clear reception.

[MrOmnos]

What is, in your view, the difference between a high power signal and a high energy signal?
(Power is energy over time.)

Yes. I know that very well. I am really confused by the whole penetration power thing. When I say penetration power I mean in space. Reading comments here makes me think penetration power depends on a lot of variables. Materials it is penetrating through, it's density and other stuff. But lets consider a concrete wall in space. What factors will affect the penetration power of a signal now?   

[joseph nicholas]

The problem with FM radio is the large number of metal objects in the wall of a typical home with dimensions comparable to a wavelength.  Wiring, plumbing, plaster reinforcing mesh on corners etc. This creates a complex self-interference pattern and moving the antennae half a wavelength to find a local maxima or a larger distance to get out of the shadow of a larger area of metal is commonly necessary to obtain clear reception.
[/quote]

I'm not really sure, but imperical evidence seems to contadict this.  Anyway I was answering the op from this point of view.

[Bud]

@op you need to do some reading on wall penetrating radars.

[MrOmnos]

@op you need to do some reading on wall penetrating radars.

Hi, could suggest me some papers to read?

[Bud]

As in any research there is no magic bullet article that will give you all of it. You have  to make your way through piles of information. Start googling for wall or ground penetrating radar, and take your time to review. You can eliminate tech journalism sources like Gizmodo, Techcrunch, Hackaday and such, do not waste your time on those, they are useless. Focus on IEEE papers and PhD thesises. Be prepared to go through some math but it is not too heavy. You need to understand the  underlying math to build your data processing software if you want to build a mobile solution. You can't drag MatLab with you everywhere.

[David Hess]

Read about pulse compression.

For simple non-bandwidth limited designs, shortening the pulse duration to raise the power while keeping the same energy will increase the signal to noise ratio and hence the range and penetration.  It is like using a brighter flashlight for a more limited time; I can see the bones through my hand with a xenon strobe light but not with a normal flashlight.  Practical low power designs use synchronous detection or cross correlation to improve signal to noise ratio.

[hamster_nz]

There is more to it than just frequency.

Taking it to absurdity....

Light is very high frequency RF.

It does not go through walls. It does however go under doors, through keyholes and through gaps in meshes in microwaves oven doors.

(Next up, Xrays and gamma radiation)

[Bud]

@3roomlab
It is certainly not for heating bodies behind walls.  Beside obvious applications such as military/urban resque there may be big market in construction/renovation industry, if a solution is portable and affordable enough. Thereis a paper describing using the technology to measure thickness of ice in Antarctica. This one may be somewhat of an exotic application but imagine cost of doing same by drilling method, GPR would save tons of money and is very portable compare to mechanical methods.
A limiting factor on the lowest  frequency would be the antenna size. So no, i do not think you can get away with 27MHz.  Perhaps   VHF would be absolute lower frequency limit for practical applications,  more of perhaps 1...3 GHz for a solution that can be developed by an individual or small company. And if it is a sweep frequency method, you need a broadband antenna. So one has to keep the antenna requirements in mind when working on this.

[Bud]

I think this Vivaldi antenna looks reasonable compromise in many aspects. And for direction and other parameters estimate of the target one probably needs two or more of them.

http://m.ebay.ca/itm/NEW-UWB4-Vivaldi-TSA-Antenna-1500-6000MHz-SDR-RADAR-SIGINT-EMC-LAB-HORN-/222327593470?hash=item33c3c1d9fe%3Ag%3A7r0AAOSw5dNWnvbq&_trkparms=pageci%253Ad3ab2a95-c09c-11e6-bd62-74dbd180a03a%257Cparentrq%253Af46595af1580a2a398683ef7ffdce294%257Ciid%253A1

[David Hess]

Beside obvious applications such as military/urban rescue there may be big market in construction/renovation industry, if a solution is portable and affordable enough.

Here in the US, our militarized law enforcement is salivating at the prospect of portable room and house scanning radar which does exist.  NYC deployed vans with the devices not long ago with the stated intention of scanning pedestrians for firearms and such which is interesting in light of the previous US Supreme Court ruling saying that such counts as a search under our 4th amendment.

The Supreme Court ruled 5-4 that the thermal imaging of Kyllo's home constituted a search. Since the police did not have a warrant when they used the device, which was not commonly available to the public, the search was presumptively unreasonable and therefore unconstitutional.

[Bud]

This portable device is rudimentary but yes i heard it caused an uproar In the press.

[Assafl]

Read about pulse compression.

For simple non-bandwidth limited designs, shortening the pulse duration to raise the power while keeping the same energy will increase the signal to noise ratio and hence the range and penetration.  It is like using a brighter flashlight for a more limited time; I can see the bones through my hand with a xenon strobe light but not with a normal flashlight.  Practical low power designs use synchronous detection or cross correlation to improve signal to noise ratio.

+1 - Yup. When we designed RADARs and SONAR systems - increasing power (even if energy stayed the same - e.g. by sending pulses) could (and indeed was) used to improve signal to noise ration.

Of course, increasing energy (at a higher system cost) would also work, but many pulse compression techniques (such as spread spectrum, wavelets, chirps and others) could be used to avoid specific problems, such as absorption at specific frequencies, and reverberation (very close to the SONAR - noise is actually a reflection from water particles, plants and animals - like krill - hence: up close - a SONAR is said to be "reverberation limited" while far away a SONAR is said to be in the "Noise Limited" zone), and even some noise sources (look up snapping shrimp for example of an egregious noise a SONAR engineer has to contend with - Horrible!).

As for increasing or decreasing frequencies - that is usually not a "linear" question (it may be for vacuum - but even then I'd select a frequency based on the size of my transmitter and receiver - and sensitivity to directivity). For a real world scenario, that depends on the ability to send and receive (size of device), ability to maintain directivity (do I need omni-directivity or can I use a reflector), through what do I want to penetrate? Does it reflect or absorb specific frequencies (I would want to avoid those). etc.