smith chart fr4

Hi All,

I have a question on smith chart performance.


I have a pcb of twin lead dipole antenna (FR4 substrate) with a hardline soldered on end of pcb and the other end of hardline soldered in n-type male connector.

I want to see impedance value in smith chart at agilent network analyzer e5070b.

The frequency range is 5.1GHz to 5.8GHz. The centre freq is 5.45GHz.

The results that i got from network analyzer is 53ohms at 5.1GHz and 25 ohms at 5.8GHz.

I can play with the antenna position bcoz im holding the antenna.

Why im getting 25ohms at 5.8GHz?

Is it ok or bad?

I attached the screenshot for ur view.


Urgently need ur reply.


Thanks .


Regards,
Chellappan.

hi all,


plz reply me....

i need ur help urgently.....

Theoretically a dipole antenna is resonating only at one frequency.
The bandwidth of the dipole can be increased, if the thickness of elements is increased or introducing some slits into the arms elements.

http://mwrf.com/Articles/ArticleID/21233/21233.html

If is possible to fold the dipole, this will help also increasing the bandwidth.

Hi ,

I attached the dish and feedhorn antenna pics.

N-type of feedhorn antenna is pluged into n-type of dish.

The pics in this file are:
1) Dish
2) Front view of feedhorn antenna
3)Back view of feedhorn antenna

Could u tell how i need to key-in value step by step in agilent e5070b network analyzer to see the smith chart performance?

The smith chart that i attached earlier shows 53ohms at 5.1GHz and 25ohms at 5.8GHz.


This practical gain for this 5.1 to 5.8 GHz are about 21dBi which comes closer to theory gain value.


But the gain is fine and i understand abt the gain but I don't understand how to see smith chart and originally what to key-in in the network analyzer. Is my steps of get the answer of smith performance gone wrong from ur view.




Pls guide me.



thanks


Regards,
Chellappan

Hi,

plz i need help from u all.


Plz explain me clearly.

Could you post FR4 specs, PCB thickness and cooper thickness , and photograph of dipole or measurements ?
You could modify impedance changing dipole distance from director (reflector).But 20% bandwith is very dificult.
I could try to test it in HFSS.

Fromm the smith chart impedance is rotating more than 5 times when frequency is changing from 5.1 to 5.8GHz.

I conclude it as bad design if the goal is wide band antenna from 5.1GHz to 5.8GHz.