far field range cst

some one please explain how to understand the far-field from simulation in cst
and what the relationship between directivity nd efficiency
thanks

Hi KYG,
i'm happy to help you, but what exactly you want to know about farfield?
About directivity and efficency, i tell you that high values of directivity suggest a good performance of the antenna, but it depends on the type of antenna. The same thing it can say about efficency: the performance of the antenna is good when the value is close to 1. Put attention on the efficency if you use materials without loss, because it's possible that efficency is plus than 1.
Good bye and good luck! And if you want other help i'm happy to satisy you!And sorry for my very bad english!

Far-field in CST:
3-D plot gives you the contour in three dimensions (by default, the maximum field/power is shown in red). For better understanding, you can include the structure along with the far-field (just right click on the 3-D pattern, plot properties -> show structure). you can also see the polar plot by cutting the plane along theta or phi axis. if you need some background on field plot, read one antenna book like Balanis.
Directivity and efficiency:
There is no relation between directivity and efficiency. however, directivity and gain are related by efficiency. Second chapter of Balanis explains the fundamental terms of antennas. Try reading that.
good luck.

Hi all,
Thanks a lot to give me information.
for fmoney,
actually i want to know how far far-field contribute for performance of antenna?
for your information i am now degree student and i am doing to design meander line antenna for range freq. 400-470MHz and problem to understand the result far-field from CST.
beside that may i know that u are cst user?
regards,
kyg

Hi shameemkabir,
i will try to find the balanis book
tq
regards,
kyg

hi kyg,
it is clear from your far-field plot that your antenna is radiating only on the upper hemisphere (planar antenna with infinite ground plane). Moreover, maximum radiation is in the direction phi = 180, theta = 0 (dark red portion in your plot). You can take a look at the 2-D pattern by selecting the plot properties -> polar (select phi = 0).
I guess it will help you.
Regards,
Shameem

what do you mean that the performance of antenna is good when the value is close to 1? do u meand close to 1 is VSWR?

what do you mean that the performance of antenna is good when the value is close to 1? do u meand close to 1 is VSWR?[/quote]
Efficency is related with the amount of radiated power. It's defined as the ratio between radiated power from the antenna and delivered power into it. So, if efficency is equal 1 all delivered power is radiated from antenna. It's an ideal condtion, but it's represent the ideal antenna.
Farfield is related with the gain of the antenna. The aperture (3db angle) in the two principal planes determine the maximum gain of the antenna.
I suggest you an other interested book "Antennas for all applications"-third edition John Kraus & Ronald Marhefka. It's interested because it's not much theoric and there are many interesting examples.

And, to answer your old question, yes i'm a CST user. I'm an antenna design in a telecommunication company and i use CST for work.
Best regards and good luck