uwb antenna discussion

[rezna]

Hi

I have only one "free to use" article which is related with Wu-king Theory (I hope it is free, because you can find it and download it from internet there: https://users.ece.gatech.edu/~wrscott/).
Other sources are not free (IEEE,..) sorry

However, Wu-King dipole is easy to describe. It is every (for example dipole structure) with this resistive loading along dipole (from port to the end of structure):

Z(x)=(60*Psi)/(h-x) where "x" is position along dipole, "h" is length of dipole, and Psi is:

Psi = 2*[1/(sinh(h/a)-C(2A,2kh)-j*S(2A,2kh)]+1/(kh)*(1-exp(-j2kh)) (it is for dipole structure where "a" is radius of this dipole)

C(2A,2kh) and S(2A,2kh) are generalized cosine and sine integrals.

 

[SAJ25]

it is os useful!! thanks a lot

 

[Azulykit]

Planar and spirals are well known for their broadband (many octaves of coverage) with modest (6 to 10 dBic) and impedance matches of 2.0:1 or better.

The feedlines seem to be giving people grief and I have extracted my comments from a recent thread on 2-18 GHz spirals:

2-18 GHz spiral antennas are available commercially from TECOM Industries among others. One might consider purchasing one to see how it is constructed. I am not advocating a direct copy. The techniques would be useful to study and then go on to a new design.

Two feed structures come to mind that maybe helpful. (I am guessing that you are probably working on a cavity backed spiral about 3 inches in diameter and about 2 inches deep.)

If you are looking for a balun I would also assume you are using a 50 Ohm coax feed (you will need nearly 5 octaves of bandwidth).

One can attach the coax to a microstrip transmission line and then gradually taper the line to a pair of (broadwall coupled)traces. Think of a transition to twin lead. The longer the better as you will need around a half wavelength at 2 GHz. The symmetric end may then be fastened to the pair of spiral arms.

Another approach is to take a coaxial cable (like 0.141" semi rigid or even smaller) and cut the shield with a long diagonal cut. You will end up with a shield looking like the business end of a hypodermic needle. The sharp end of the taper and the coax center conductor now form a balanced line. These are fairly easy to fabricate if you have access to a friendly machine shop. There is the risk of slight beam squint with this one. This feed is also used in two arm conical spirals.

If HFSS is available experiment to refine the dimensions.

Corzine and Mosko's book "Four Arm Spiral Antennas", Artech House Antenna Library includes a wealth of information on various spirals. (I have a paper copy only.)

 

[ayy2023]

hi all
i'm currently designing an equiangular spiral antenna operating between 2-14 ghz at ansoft hfss and researching for different parameters for my undergraduate finishing project
it has 2 arms
what my problem is it has vswr around 10-15 without a balun.
are these values useful in real life? they seem to big to me.
if not then what should i do? do you have any idea how i could design a balun for it via HFSS? and is it proper to design spiral antenna with balun? my project advisor forces me to search for all cases and to see if it is ok without a balun or not.
Thanks in advance.

 

[Azulykit]

Among other things a balun is a device that transforms a balanced transmission line structure to an umbalanced one. Think of coax and twin lead as an example. If you are feeding the spiral with a balanced line then the balun is unnecessary. If you feed the spiral with an umbalanced line there will be additional loss to the overall performance because the two arm spiral is a balanced structure.

 

[oxs657]

hi, i was wondering if anyone could help me.I am building a square microstrip antenna operating in the 1-3GHz bandwidth.i have simulated multiple versions in CST but all my results for the s-parameters are wrong.i have looked everywhere but cant seem to find any help especially on how to come up with dimensions so i just made some up...maybe that might be the problem...please any help would be appreciated thanks in advance..

oh and i am not using a balun but a feedline with a coaxial

 

[SAJ25]

dear oxs657
the squared patch antenna has a very narrow band width abd 1-3 GHz is not possible!

 

[oxs657]

oh sorry i meant a square spiral not just square

 

[eng_romeo]

Dears,

I tried many times to simulate monopole ultra wideband antenna using IE3D program but i failed and i want know the reason so i attached file that indicates figure design and S11 result for antenna design but my result is different that gives multiband frequency.

ε r = 4.65 , h = 1.5 mm

The dimension of the ground plane is chosen to be (30 x 11.5) mm2 in this study.

The original design has a rectangular radiator with a width (w) of 15 mm and a length (l) of 12 mm.

The feed width (wf) is set to be 3 mm and the feed length (fl) is set to be 12.5 mm. The first and third notch dimensions are (1 x 1) mm2 and the second notch is (1 x 1.5) mm2.

 

[SAJ25]

dear romeo
1- are you considered the finit or infinit ground plane? it is too important.
2- are you considered the lambda/4 condition for simulation?

 

[eng_romeo]

Dear SAJ25,

1- I considered finite ground for antenna design.

2- How can i consider lambda/4 in simulation?

Thanks.

 

[SAJ25]

you should use a vacume that it is larger than from the maximum size of your antenna about lambda/4
and it is better to use an infinit ground plane

 

[Leilon]

Hi all,
I am working on UWB antenna too, on planar structure, I tried to simulate one article with HFSS, but my result is wrong!
I think for correct result i must consider feed effect, but I do not know how i do!
for more information visit this,
**broken link removed**

 

[panda.asit]

hi all,

im doing project on (3×3 ) sierpinski gasket fractal array antenna for UWB comminication using ie3d.

can any one who help designing sierpinski gasket fractal array antenna using ie3d.

i hv already design sierpinski gasket fractal antenna but while making it into array , problem occure
plz help me , my id is panda.asit@gmail.com