Differences between measured and simulated results of antenna efficiency

[YechielA]

Hi,

I simulates a simple printed Inverted -F antenna at a frequency of 1.9 GHz using HFSS. I also measured the antenna in an anechic chamber.
The problem is that I get a large difference between simulated and measured results. While measured results show antenna efficiency of about 66%, measured results show no more then 27%. The printed antenna is printed on FR4 which is assumed to have a TAND of 0.02.

 

[Umar608]

Hi,

I also have similar observations. I measured several printed antennas in an anechoic chamber. In some cases, the results were close but in other cases, there was a huge difference. HFSS gave a 94% efficiency of a printed monopole designed on FR4 substrate. However, when measured in Satimo anechoic chamber, the actual efficiency was only 56%. For the patch antenna, the measured readings were mostly the same.
If you get to know how to get accurate efficiency with HFSS, please share.
Also there is a Wheeler's cap method to test the antenna efficiency using network analyzer. I never get the correct reading using that method. If anyone knows about this method, please share.

 

[YechielA]

"Wheeler's cap method" - didn't hear about it. I'll learn about it. There is a small test equipment also provided by EMSCAN called RFX/RFX2 for efficiency and radiation pattern. it does a near field to far field transformation.

 

[Umar608]

You may find the following references useful in knowing about 'Wheeler Cap's method '

https://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6393764&tag=1

https://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=4294547

 

[YechielA]

I'll read this, thanks.