Bifilar Helix Antenna with Reflector

[TheMaksimys 2]

Hi everyone,

I am attempting to make this antenna to work for ISM band (868-915 MHz). It seems that I am having troubles with the feeding structure, since the measured Return loss barely represents what I observe in simulations. The antenna is designed for the characteristic impedance of 200 ohms, so I am using the Mini-circuits 4to1 balun and connecting the balanced side rigth to the ends of helix, just as in the simulation. I cannot really find the reason for the discrepancy in the results, since even if I am feeding the antenna with unbalanced 50 Ohms it still demonstrates the return loss that is way off from the simulated results. I am attaching the simulation file and a few photos of the prototype. Thank you for everyone who will contribute to the discussion of this topic!

 

BFHA_tests_3.cst

[Admin 2578]

,,,hi buddy...!!!

,,,you can try to do Clanon's impedance matching...

 

[TheMaksimys 2]

1 hour ago, Admin said:

,,,hi buddy...!!!

,,,you can try to do Clanon's impedance matching...

 

Unfortunately not really an option, since I was looking for a wideband solution, but thank you for pointing me to this post!

[Admin 2578]

,,,,these would be the results on your Bifilar Helix Antenna....!!!

[Andrew77 11]

On 12/06/2024 at 9:04 PM, Admin said:

,,,,these would be the results on your Bifilar Helix Antenna....!!!

Hi Dear, Please could you send me the *.stp file? Because I'm using CST2019, Many thanks! Andrea

[Admin 2578]

Andrew77...

I don't know if this can help you....!!!

double helix.stl

[Andrew77 11]

Yes, It Works!

 

Have a nice day!

 

[Andrew77 11]

Have you tried to get the GND closer to the antenna? VSWR gets better! In this case GND plate moved to the antenna by 6 mm

[Andrew77 11]

Hi,

further improvements for the matching: check this

[Admin 2578]

You can put the CST-file...??