Impedance matching log-periodic

Hi members

I am working on log periodic desig. I got stuck on impedance match . I am using CST for simulation. How can I avoid using a balun for impedance match, feeding method or diameters affects it.I want to use 50ohm Coax. Experts plz share ur knowledge on that problem


Thanks

Impedance matching is needed when antenna impedance not match system impedance. No need for a balun for that reason even if a balun can be used in a such way.
If your log periodic antenna is a balanced design and you feed it with a unbalanced cable will it affect your antenna as cable will be a part of total antenna structure.
A correct designed balun avoids that, not the opposite, so I do not understand your problem. Can you give some more details?

Thanks for ur reply . During my simulation when I set 200ohm in discrete port it gives vswr less than 2 but when i set 50ohm it gives vswr more than 2ohm. In literature i also found that log periodic have typically an impedance of 200 ohm. some also mentions adjusting dia to length ratio. so how will tackle this impedance mismatch during my practical design without using balun

---------- Post added at 17:12 ---------- Previous post was at 17:10 ----------

Thanks for ur reply . During my simulation when I set 200ohm in discrete port it gives vswr less than 2 but when i set 50ohm it gives vswr more than 2ohm. In literature i also found that log periodic have typically an impedance of 200 ohm. some also mentions adjusting dia to length ratio. so how will tackle this impedance mismatch during my practical design without using balun

You can adjust impedance depending on a lot of design details. Most common is to design for 50 Ohm. At 200 Ohm is it maybe something like this type of log.per.antennas or a helix-type you is designing?
VSWR is unitless btw.

Because the log periodic use a bunch of parallel dipoles, its impedance is actually lower than of a λ/2 dipole (which is about 73 ohms)

I am designing a dipole array type. And i want to use a 50ohm system. so what are the design changes i should make that my simulation will show good vswr . I was also reading somewhere mentioning use open feed wire for avoiding balun.