Are Microwave Signals More Susceptible To Obstructions

[Victor43]

I am hoping anyone might be able to tell me if Microwave signals are more susceptible to obstructions like wooden walls and floors if used for indoor applications like a wireless video camera ? I am not an engineer so please use basic terminology.

Thanks

Victor

 

[albbg]

There are studies about the propagation in indoor condition and about the attenuation due to obstacles like foliage. In general the higher the frequecy the higher the attenuation due to obstacles.

 

[reidintransit]

compared with what? in general higher frequency is going to be more susceptible to losing signal power. floors won't matter unless going between levels. any change in materials is going to cause some of the signal to get reflected. Distance is also a factor even without obstructions.

 

[jiripolivka]

Your question is a bit difficult to answer in an easy way. Microwaves can be compared to light waves, and then the size of obstructing bodies must be scaled according to the wavelength.
Radio waves and microwaves are used best if propagated in a free space without obstructions. If you try to transmit indoors by microwaves, the obstructions like walls, corridors, etc, cause multiple reflections. These reflections split the transmitted wave into several independent waves that arrive to the receiver with "delay spread" causing a confusion in the receiving process. If you emit a short pulse (typical in communication), then several such pulses arrive to the receiver and the receiver or decoder fails to understand which pulse is which.
This problem was only resolved recently by using the MIMO concept. MIMO uses several transmitter-receiver pairs with antennas and by a special processing it can operate in the confusing indoor situation quite well.

 

[biff44]

here is a decent article:
https://www.eetimes.com/document.asp?doc_id=1276321

The second equation shows that the power received at the far end is directly proportional to the wavelength squared. As frequency goes up, wavelength goes down, so right off the bat you are fighting physics to send a higher frequency signal vs a lower frequency one.

That said, it is a little easier to make a high gain antenna at shorter wavelengths, which helps some. But if you have an omnidirectional antenna need, that size shrinkage will not help, your antenna gain will be fixed at somewhere between +3 to -10 dBi.

ALSO as the wavelength shrinks in size, the microwave signal is more easily influenced by small objects...bits of iron in a concrete wall, nails, refrigerators, etc, so there is more loss and more re-reflecting of microwave signals before they reach the receiver.

 

[Darktrax]

It all so much depends on what is in the walls, etc. As example, I got a startling return loss from a feed-horn that happened to be pointing straight at a wall. The insulation inside the cavity wall was polyurathane foam supplied as boards covered both sides in aluminium foil. For the RF - it may as well have been a mirror.

The stuff is much used in roof insulation as well, to the extent that mobile phone services sometimes need an external antenna, with arrangements to provide in-building coverage. It is also no surprise that GPS sat-nav function is compromised in between tall buildings in big cities.

 

[Victor43]

There are studies about the propagation in indoor condition and about the attenuation due to obstacles like foliage. In general the higher the frequecy the higher the attenuation due to obstacles.

Many thanks for the reply. That is what we had thought.

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compared with what? in general higher frequency is going to be more susceptible to losing signal power. floors won't matter unless going between levels. any change in materials is going to cause some of the signal to get reflected. Distance is also a factor even without obstructions.

Thank you for your reply. Actually we were thinking of where the signal passes through floors and walls.Comparing the frequency of microwaves to radio waves that are outside the range of microwave.

- - - Updated - - -

Your question is a bit difficult to answer in an easy way. Microwaves can be compared to light waves, and then the size of obstructing bodies must be scaled according to the wavelength.
Radio waves and microwaves are used best if propagated in a free space without obstructions. If you try to transmit indoors by microwaves, the obstructions like walls, corridors, etc, cause multiple reflections. These reflections split the transmitted wave into several independent waves that arrive to the receiver with "delay spread" causing a confusion in the receiving process. If you emit a short pulse (typical in communication), then several such pulses arrive to the receiver and the receiver or decoder fails to understand which pulse is which.
This problem was only resolved recently by using the MIMO concept. MIMO uses several transmitter-receiver pairs with antennas and by a special processing it can operate in the confusing indoor situation quite well.

Wow nice to know information thanks.

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here is a decent article:
https://www.eetimes.com/document.asp?doc_id=1276321

The second equation shows that the power received at the far end is directly proportional to the wavelength squared. As frequency goes up, wavelength goes down, so right off the bat you are fighting physics to send a higher frequency signal vs a lower frequency one.

That said, it is a little easier to make a high gain antenna at shorter wavelengths, which helps some. But if you have an omnidirectional antenna need, that size shrinkage will not help, your antenna gain will be fixed at somewhere between +3 to -10 dBi.

ALSO as the wavelength shrinks in size, the microwave signal is more easily influenced by small objects...bits of iron in a concrete wall, nails, refrigerators, etc, so there is more loss and more re-reflecting of microwave signals before they reach the receiver.

Thank you for your reply. Very helpful and understood.