the effects of mobile waves on body and human

Hallo

I would like to know the effect of human body on the mobil antenna
and how can we make the antenna insenstive to this effect
is this a problem for a wide band antenna

thanx

Hi:

the effect of mobile antenna is independent of frequency but depends to power of transmitted and reciever signals .
in past , and in the 1'th generation of mobile communications systems this problem was too serious because of the density of large power which used in those systems but in the 2'th and 3'th generation of mobile communication systems it is not as serious as in past . if you want to understand easily and so simple about the affect of power on the human body you can refer to Microwave Ovens .

regard.

The human body works as a barrier, mainly in high frequencies, because of skin depth. As larger frequency, the penetration capacity is smaller and more susceptible to obstacles. Generally in mobile applications it isn't a problem because you have signal in all directions. For human body the more close the frequency goes to 2,4GHz worse, because this is the water resonance (and body is 75% of water).

In wide band antennas you can't eliminate the effect ... because it is an electromagnetic characteristic.

most important to me is the effect of the body on the input impedance of the antenna
does any body know how to make minimze this effect

Antenna scatter wave in difference radiation pattern based on the types, like monopole, dipole, or spiral antenna, etc.
I guess it can influence the efect of the body (?)

I think is so difficult, because this effect is different at person by person, relative position, etc. You can have a system that vary the input impedance, in an determined range (obtained with measures of this influence), then the system choose the impedande that give the maximum power transfer (you have to measure the input power) avoid reflections and have maximum efficiency. It isn't simple, but it's possible to do.

I think you can refer to some papers with such title, the effect of the body to the performance of the antenna in IEEE. The effect of the body to the performance of the antenna is a hot subject in celular antenna.

I think this issue may be very usefull: IEEE APs, June 1998, vol. 46, #6.

read the information in K. Fujimoto/J.R.James,"Mobile Antenna
Systems Handbook", Section 6.1.1, pp. 295- xxxx
In essence the effect of the human body on the antenna is act
as a ground plane consequently modifying the pattern and the
input impedance. Some people say the best antenna for would
be a loop since a dielectric (the human body) will not modify
the impedance for much.

I need papers about this particle.

I need an e-book or an article about the safety of mobile phone & the interactions between EM waves and human body.

To study about the safety of mobile phone and other EMF sources to human boby you should research first in the site of World Health Organization:
http://www.who.int/en/
There are plenty of material on this subject.

I think he is not asking whether radiation will do harm to human body but how to make a insensitive antenna.

I have tested some stub antenna's far field strength.It should be noted that as the frequency as high as 2GHz ,the H plane filed distribution is not a cirlce at all. With hand or head effect, the antenna directivity would get worse. In some direction the E strength is 20 dB lower than average. Helical antenna is not so good as in lower band.

I just think you should increase the radiation area of the antenna, choose some other form antenna shape to avoid the human body effects.

I agree with you that all the discussion is about interaction between antenas and human body, but the last guy mentioned "safety" so I though he was concerned with harmful effects, sorry if I misunderstood.

Interaction in between mobile antenna and human body is still a topic many paper working for. Most papers talk about SAR health issue. I remember before I saw a paper saying that talking mobile while stand beside the wall would be helpful to alleviate the EM effect. But in terms of wireless RF performance, by different design, some mobile would loss call-in or drop call-out just because the antenna be a proximity to ear or head, which means head can absorbe magnetic power radiated by mobile or base station. Pls keep in mind that the whole mobile phone should be seen as an Antenna ! and try to keep it away as possible while using it.


wilson

any one have the permitivity coductivity and permiability and loss tangent of human body in VHF-UHF bands?

go to:

https://www.edaboard.com/viewtopic.p...374&highlight=

A long time ago I made a prototype antenna that was a slight variant of a monopole with a conical skirt for a helmet mounted application. It worked pretty well and was relatively insensitive the helmet.

The arrangement was so silly looking that we decided not to build one for real. The jokes just never stopped. It was probably the correct decision.

The best way to minimize interaction with a body is to shape the radiation pattern so that the body is not illuminated and even that does not work really well.

The human body aboser some RF power. So if you measure the radiation pattern you will find the pattern is not uniform since some power is absorbed.

THe hand holding the mobile phone is also affect the return loss. You should measure return loss with a phantom for more accurate result