Dear Luciana,

Far field zone depends on wavelength and also on antenna size vs wavelength (which is usually strongly related to antenna gain). So perhaps you are talking about over 900MHz range and under 10dBi gain antennas, if 3m is in the far field zone. Maybe these will be usefull for issues regarding far vs near field criteria:

http://www.edn.com/contents/images/150828.pdf

www.home.agilent.com/upload/cmc_upload/All/NSI-near-far.pdf

Your question is a little bit too general, and I am not sure what is your project about.

You can find a very simple approach for BTS antennas in this paper:

http://dlibra.itl.waw.pl/dlibra-webapp/Content/569/JTIT-2003_1_41.pdf

This is usefull for computing surrounding field in an area near an antenna, in the transition zone between near and far field. If the geometry of the surrounding enviroment of the antenna is complicated, it's better to go directly to the numerical approach (like MoM). Massive or multiple objects in the near area will strongly modify the antenna far field diagram anyway (and even antenna impedance). Usually you need to take into account the soil reflection, so if you are gonna solve the problem analitically, you will use at least a two ray model.

If you want far field diagram of an antenna from near field measurements, there is a MatLab routine which is doing the conversion:

http://nf2ff.sourceforge.net/

For conversion between far- and near- field there are a lot of papers, one of the oldest (and simplest, as far as I know) is Brown, J. and Jull, E.V. (1961) The prediction of aerial radiation patterns from near-field measurements - you can easy Google it.

Hope it helps.

Regards,

Teo

Dear Luciana,

Far field zone depends on wavelength and also on antenna size vs wavelength (which is usually strongly related to antenna gain). So perhaps you are talking about over 900MHz range and under 10dBi gain antennas, if 3m is in the far field zone. Maybe these will be usefull for issues regarding far vs near field criteria:

http://www.edn.com/contents/images/150828.pdf

www.home.agilent.com/upload/cmc_upload/All/NSI-near-far.pdf

Your question is a little bit too general, and I am not sure what is your project about.

You can find a very simple approach for BTS antennas in this paper:

http://dlibra.itl.waw.pl/dlibra-webapp/Content/569/JTIT-2003_1_41.pdf

This is usefull for computing surrounding field in an area near an antenna, in the transition zone between near and far field. If the geometry of the surrounding enviroment of the antenna is complicated, it's better to go directly to the numerical approach (like MoM). Massive or multiple objects in the near area will strongly modify the antenna far field diagram anyway (and even antenna impedance). Usually you need to take into account the soil reflection, so if you are gonna solve the problem analitically, you will use at least a two ray model.

If you want far field diagram of an antenna from near field measurements, there is a MatLab routine which is doing the conversion:

http://nf2ff.sourceforge.net/

For conversion between far- and near- field there are a lot of papers, one of the oldest (and simplest, as far as I know) is Brown, J. and Jull, E.V. (1961) The prediction of aerial radiation patterns from near-field measurements - you can easy Google it.

Hope it helps.

Regards,

Teo

Near and far field are transmission region for time varying electromagnetic field propagation. EM field changes in character with distance from its source is that Maxwell's equations prescribe different behaviors for each of the two source-terms of electric fields and also the two source-terms for magnetic fields. Electric fields produced by charge distributions have a different character than those produced by changing magnetic fields. Similarly, Maxwell's equations show a differing behavior for the magnetic fields produced by electric currents, versus magnetic fields produced by changing electric fields. in far field radio waves, microwaves of different wavelength includes which require antenna. since transmission distance is directly proportional to the square root of height of antenna. frequency is inversely proportional to the wavelength and hence frequency is inversely proportional to length of antenna. for shorter wavelength frequency is more and thus height of antenna is less, for greater wavelength frequency is less and thus height of antenna is more. E.g if frequency is 38 GHz antenna of length 1.2 meter is to be used. Refere Occupational Safety and Health Administration, Cincinnati Technical Center (May 20, 1990). "Electromagnetic Radiation and How It Affects Your Instruments. Near field vs. Far field

I suggest using Fourier transforms. If you already have the near-field pattern, then you may apply Fourier transforms to generate the far-field pattern at any distance. here is an example:

http://www.jpier.org/PIER/pier73/05.07031903.Costanzo.D.pdf

Hi @Teodor Petrita

I tried to run the matlab code but it seems that some of the files are missing.. ex. .mat files. Could you run it?

Dear Maryam,

I don't have acces to a licensed Matlab computer now and I have eventually go to convert these files to Octave (or go to UPT labs maybe). I am sorry I cannot test the software this week. The mat files require are at that page at the datasets section (http://www-personal.umich.edu/~vcaeken/DATASETS.zip). There are two datasets for two polarisations of one antennas. I didn't succeed to load them in Octave -there may be an compatibility issue-, but you can eventually try to load them in Matlab (see load command). Also, use the full path of the file or use the addpath command to add the path of the file to the search path of Matlab.