Clculating antanna directivity

[john54]

antanna

Hello,

I would just like to ask a simple question. I can't find the formula for calculating antenna directivity from two radiation patterns. Both polarizations are measured from -180:180 degrees, step 1 degree. So basically I have 360 numbers for each polarization.

So if anyone can help me how to compute directivity from this numbers, it would be very much appreciated. I have matlab, but if there is any other software or some other way to do this, it is also great.

Thank you in advance.

 

[mauloftin]

directivity calculation pattern

Hi,
I´m not sure, if I understand you exactly, so you want calculate directivity or radiation patterns ? and "...directivity from two radiation patterns..." you think, that you have two polarization or two antenna ? and "360 numbers" are what ? Axes X is degrees, and axes Y is what ? U,I, E ... ? Directivity is only maximum. Can you more specify your requirements ?

 

[john54]

cross formula for directivity

Sure.

I have two radiation patterns. One in E plane and one in H plane. Each radiation pattern consists of 360 numbers (for each degree one number). So I have 360 numbers for E plane and 360 numbers for H plane. So my question is which formula should I use for computing directivity from both radiation patterns (E-plane, H-plane). I hope it is more clear now.

 

[mauloftin]

c program on directivity

OK,
so radiation pattern E plane and H plane is not same as "two polarization". Do you now, what is directivity ? Directivity is usually max radiation pattern. And the max is the same in E plane as H plane. So you must find only max in E (or H) and you have directivity. But do you know what is "number" ? "each degree one unumber", number is Voltage or Current or E ... or what ?

 

[john54]

why directivity is so important

hmm...
E-plane, H-plane (vertical and horizontal polarization)=2 polarizations..

Directivity:
It measures the power density an actual antenna radiates in the direction of its strongest emission, relative to the power density radiated by an ideal isotropic radiator antenna radiating the same amount of total power.

So you must find only max in E (or H) and you have directivity.

It is definitely not so simple..

"Numbers" are P(received) [dBm]...

 

[mauloftin]

directivity matlab

OK,
yes, definition directivity is absolutly correct, so it is only one number, it will be the same in E plane and H plane. You must only find direction with strongest emission, and there is number - in dBm, so you can calculate directivity from Friis transmission equation (https://en.wikipedia.org/wiki/Friis_transmission_equation), exactly Gain, but Gain is nD where n is efficiency of antenna and D is directivity. Are you understand me ? it is easy

And polarization is not the same as radiation pattern in E plane and H plane, radiation pattern in E and H are only cut 3D radiation pattern! Has nothing in common with polarization. You can measure co-polar in E and H plane and cross-polar in E and H plane, are you understand ?

Added after 1 hours 10 minutes:

So I hope, that I helped you, If yes, click on "Helped me"

 

[john54]

determine directivity from radiation pattern

You still don't understand... Yes I know this, but this equation has two unknown variables..(Gt,Gs).. also I don't have distance...

What I am asking is how to calculate directivity from E and H plane of the radiation patterns. I know it is integral of both planes...

 

[Aya2002]

calculate directivity

hi friend, please see this link

 

[john54]

h-plane e-plane wikipedia radio frequency

Aya2002 MANY THANKS!!!!!!! This is exactly what I was looking for!!!!

Just one little think I don't understand:

% Input parameters:
% 1. TL, TU: Lower and upper limits in theta (in degrees)
% 2. PL, PU: Lower and upper limits in phi (in degrees)
% 3. U(theta,phi): The radiation intensity function (in file 'U.m')


The radiation intensity function F must be provided for a given antenna, and should be inserted into the subprogram U.

% **Example**
% y = sin(THETA).*(sin(PHI)).^2;

How can I insert my numbers into U.m file? I don't have any function..just numbers?

Thanks.

 

[Aya2002]

formula of directivity in degrees

in which chapter you faced this, may be (may be) i can help u

 

[john54]

finding directivity equation

chapter 2 - Directivity..

function y = U(THETA, PHI)
% **Example**
% y = sin(THETA).*(sin(PHI)).^2;

 

[Aya2002]

matlab directivity by full pattern integration

your numbers will represents the variable in the subprogram U.m.

Hence,

y=your numbers;

thats it

 

[john54]

directivity edaboard

hmm..I don't quite understand.. I have two radiation patterns:

1)Phi=0, Theta=0:360
2)Phi=90, Theta=0:360

for each radiation pattern there are 360 numbers. "y" is only one variable, so how can I insert two planes simultaneously?

Or if I insert numbers just for one at one time than which angels should I use for theta and phi:

1. TL, TU: Lower and upper limits in theta (in degrees)
2. PL, PU: Lower and upper limits in phi (in degrees)
*EXAMPLE: If the antenna is radiating only in the upper hemisphere, the input parameters are TL = 0, TU = 90, PL = 0, PU = 360.

1)Phi=0, Theta=0:360:

TL=0, TU=360, PL=0, PU=0 ?

2)Phi=90, Theta=0:360

TL=0, TU=360, PL=90, PU=90 ?

 

[Aya2002]

directivity function+matlab

my friend,
As i see, there must be a relationship between theta and phi so that by this relationship you can put your data in the variable y.

Added after 4 minutes:

my friend, do not forget that i am poor in this field. I am interest in the digital communications

Added after 1 minutes:

you must have this relationship:

F(THETA, PHI): the radiation intensity function

c **Note:
c The radiation intensity function F must be provided for a given
c antenna, and should be inserted into the subprogram U.

 

[john54]

antenna directivity formula,wikipedia

dear friend, i really appreciate your help!

I don't quite understand what you mean.. Is it possible to calculate the radiation intensity function F(THETA, PHI) from two radiation patterns which I have?

 

[Aya2002]

directivity h(theta)

see the attached file

 

[Aya2002]

e and h plane picture

now the relationship is equation 2-12a

Added after 2 minutes:

please friend do not forgive me. This is what i see and as i tolled you that i am not interest in this field

 

[mauloftin]

am antana

You still don't understand... Yes I know this, but this equation has two unknown variables..(Gt,Gs).. also I don't have distance...

What I am asking is how to calculate directivity from E and H plane of the radiation patterns. I know it is integral of both planes...

OK, sorry
I was thinking about it this morning and I rememberd what do you think But so I want to write it, but Aya2002 was faster, and certainly better. I was thinking about it in "practical mode" and you need "mathematical mode" , sorry
Yes, once upon a time I did similar m-file.... but it is long time

and is it correct ? It think, that was cleaned

Added after 5 minutes:



And I rememberd, there is very good source for antenna and so on

https://www.ece.rutgers.edu/~orfanidi/ewa/

for you is ch15, there is matlab code also

 

[Aya2002]

i can send it by a private email cos i downloaded it before it to be cleaned.

 

[john54]

The post has been cleaned, but here is the same topic, where you can download this programs that we discuss:



mauloftin: do you still have this m file, or do you remember how this think worked?

I still haven't figured out how to insert my data to program...