Mircrostrip Patch Antenna Efficiencies

Hello Forum,

Are there any good anlayitical models on how to compute microstrip patch antenna efficiencies? There is a comprehensive discussion on this in "Microstrip Antenna Design Handbook" by Ramesh Garg, et al.

But I noticed that these models underestimate dielectric losses. For e.g for a rectangular patch antenna operating in TM10 mode on a FR4 substrate, the model predicts an efficiency of 85%. But most measured results report somewhere between 40 - 50%. I measured one such antenna in an anechoic chamber myself and got 49%.

I am trying to predict the efficiency of an antenna build on a high permittivity material (e_r of 40- 50) at a frequency of 2.4 GHz. I believe that most materials in this region are polymers and their loss tangents are no better than FR4. So I would expect a lower efficiency. But with the analytical model I get somewhere around 40% which I am sure is quite high.

Any inputs / references would be greatly appreciated.

Thanks in advance.

Look into a device called a Wheeler Cap if you want to measure efficiency.