[Need Help] Rectangular Microstrip Antenna

[dong86]

rectangular microstrip antenna

CAn any1 pls help me figure out what is my problem??

I've design a 886Mhz rect. microstrip antenna and stimulate by using microwave cst!
W(patch)= 10.52cm
L(patch)=8.4cm
h=1.6mm

w(feedline)=3mm
l(feedline)=4.75cm

Substrate=(20cm*17.8cm)
relative permitivity=4.4

from the graph that i attached! return loss how come wont goes up to 10db or more?

 

[mauloftin]

Hi,

of course. You have problem with matching.

follow



Added after 5 minutes:

If you use quarter-wave transformer, do not forgot draw 50 Ohm feedline before quarter-wave transformer (**broken link removed**)

I hope, that I helped you.

 

[tyassin]

Hi

Dont you have another problem like S11 greater than 0 dB. It could be that some seup in CST is not correct.

 

[mauloftin]

Hi

Dont you have another problem like S11 greater than 0 dB. It could be that some seup in CST is not correct.

Hi,

i think, that it is normal problem, it is about accuracy. It will be better use adaptive meshing or Frequency domain solver.


may be, dong86 you can see at the attachment.

 

[dong86]

Hi mauloftin,

I'd like to say "tq very much".. hehe

ya.. its about matching problem! anyway, i m not really know how to calculate L1, how long it should be?? and the distance between substrate and patch must greater than lamda over 4??

 

[mauloftin]

Hi mauloftin,

I'd like to say "tq very much".. hehe

ya.. its about matching problem! anyway, i m not really know how to calculate L1, how long it should be?? and the distance between substrate and patch must greater than lamda over 4??

Hi,

you can use:

1) λ/4 transformer: **broken link removed**

2) another type of matching: - The L1 you must find it experimentally.


ad 1) - length of λ/4 transformer is λ/4 . You can see at the , there is all about λ/4 transformer

I wrote:

You must use software TXLine

1) find impedance your microstrip antenna - easy, set right colum "Physical Cahrakteristic" and click left arrow - you have impedance Zm

2) calculate Zx = √(Zm*50), this is impedance λ/4 transformer

3) in left colum set Zx, electical length is 90 deg - click right arrow and you have design λ/4 transformer

4) set left colum 50 Ω and you have feedline. In this case the length of feedline is
not important, you can have it 50 mm or 50 cm or 4.35 km (if you have loss free material)