formula width of microstip

hi guys :
i am a newbie and want to know when we design a microstip /patch antenna , how should we set the width and length of the microstrip , supposed it is edge feed .
well, i write some parameters as following:
supposed we have set dielectric constant :Er =4.4 , the heightof substrate is : h=0.794mm the center frequency is :fr=2.4GHz
then i write a matlab code according some formula from a MS antenna book:
Matlab code :
------------------------------------------------------------------------------------------
fr=input('Please enter resonant frequency in Hz : ');
Er=input('Please enter the relative dielectric constant of the substrate : ');
h=input('Please enter the height of the substrate in m : ');
c=3e8;
Lambda0=c/fr;
W=c/(2*fr)*[1/sqrt((Er+1)/2)]; % the width of the patch
Ee=(Er+1)/2+(Er-1)/2*[1/sqrt(1+10*h/W)]; %dielectric in substrate
Lambda_g=Lambda0/(sqrt(Ee)); % lambda in dielectric
delta_l=0.412*h*(Ee+0.3)*(W/h+0.264)/(Ee-0.258)/(W/h+0.8); %fixed length
L=0.5*Lambda_g-2*delta_l; % Length of the patch
WG=W+0.2*Lambda_g; % width of the ground/substrat
---------------------------------------------------------------------------------------------

and now my question is how to get the width of the stripline and its length ?
is there are some formula ?
Thanks in advance.
sunmoonstar

U can use programm AppCad to get the width of the stripline . The length is calculated to match the circuit

Hi Sunmoonstar,

you can learn how to do this by reading Antenna theory by Balanis pg 722-735.

Cheers,
Element7k

Dear tieuquaybk and Element7k:
thanks for your help .
ok , i have seen Balanis's book"Antenna Theory" and find some more formula .
but according the example 14.2 at page 734-735.
when calculating the G1 and G12 , the two formula are in (14-12)(14-12a) and (14-18a) , but i can't use Matlab to write the codes for these two formula . Anyone can help me ?

U can use AWR free TXLine Calculator...

http://www.appwave.com/src/products/TXLine.zip

TX-Line Transmission Line Calculator
TX-Line is a free, easy-to-use, Windows-based interactive transmission line calculator for the analysis and synthesis of transmission line structures. TX-Line enables users enter either physical characteristics or electrical characteristic for common transmission medium such as:

Microstrip
Stripline
Coplanar waveguide
Grounded coplanar WG
Slotline
TX-Line has an easy-to-use interactive graphical user interface and runs on Microsoft Windows 2000/XP.

Dear Manjunatha_hv
i have a question :
does the software : "TX-line "calculate the microstrip always correctly when in higher frequency between 3-10GHz, because the character impendence is a funtion of frequency .
and another question:when i use it , the width i calculated at each frequency has a small difference. so if i have want to achieve to the impendence match, which "width" of the microstrip i should take ?
following are three width values:
3G -----Width of microstrip is 2.84mm
5G -----Width of microstrip is 2.91mm
10G-----Width of microstrip is 3.0mm

Thanks a lot
kaka

Hi,

yeah for sure your sinthetised microstrip width would not match all of the frequencies. Usually it is not the only element of matching network and things tend not be perfectly matched in such a wide bandwidth anyway so this problem is the one that someone should live with in reality.

flyhigh