Loss tangent impact in patch antenna

Hi all,

I simulated one UHF patch antenna with FR4 sub and found the much impact of the loss tangent. When loss tangent is 0.02, the Gain is only 1.2dBi,efficiency is only 28% .When i changed the loss tangent to 0.002, the Gain is 5.8dBi and the efficiency is 80%.

My question is that is there any methods to improve above performance except using low loss tangent substrate to replace FR4. thanks!

There is some problem with your simulation. Please cross-check the accuracy and meshing parameters.

rf1008 has responsed about your figures. I'm not sure how rf1008 arrives at that conclusion (it would be helpful if they state it), but I'm not disputng rf1008's statement.

But the other issue you will have is that patch antennas are usually quite narrow band, but the permittivity of FR4 is not well controlled, so the resonate frequency can vary a lot from one antenna to another.

I simulated the same model in HFSS and CST and found the similar results, when loss tangent is 0.02, the Gain and efficiency is very low.

Basically, your observation is right. The radiation efficiency of patch antennas fabricated in FR4 is low. However, there are several ways to improve the radiation efficiency, at least to some extent.
1) To optimize (roughly saying, to increase) the patch width. For thin substrates the radiation efficiency is improved by making the aspect W/L larger.
2) To optimize the substrate thickness. An optimum substrate thickness exists for a specific substrate permittivity.
3) Last but not least, there are some antenna structures seems to promising for radiation efficiency improvement, e.g. center-fed dual-PIFA antenna.

Is it a viable option for you to use foam substrate? You can also use a copper plate placed with some plastic studs.