While simulating the UWB antenna, usually it is found that the peak gain is found less (which nearly swings between 1-3 dB), and the gain seems to be increasing as frequency increases. Is there any reason behind this?
Even the S11 characteristics showing the very minimum return loss (about -30 dB) in the lower UWB band (such as 3.2 GHz etc) the gain is seems to be more at the frequency at which comparatively higher return loss exists.
Your antenna has its electrical size increasing with frequency, therefore the general trend concerning its gain is also in this direction. That'd be the main reason in my opinion.
As frequency increases directivity will increase......... This will increase the gain as frequency increases.........
Dear Anilkumar,
It would be more useful that you display S11 and the antenna gain as a function of frequency. Yes as the reflection coefficient decreases means that more power may be delivered to the antenna for radiation. To see the effect of S11 you have to transform it from the dB scale to the absolute value scale S11= 10 log Pr/Pi, then Pr/Pi= 10 ^ S11/10. For -10 dB, The ratio of the powers= 1/10, and in case of -30dB, The power ratio will be= 1/1000, So in the first case about 0,9 of the input power is passed to the input of the antenna and in the second case about 0.999 of the input power is passed to the antenna input. So, in both cases the power delivered to the antenna makes out most of the input power.
So, it seems that gain increase with the frequency is the dominant factor as the colleagues hinted.
Best wishes
From the phrasing of your question, you are probably suffering from the dubious terminology used in this field. Antenna "gain" is mostly about directivity -- the ability to point the signal in a specific direction -- and not about increasing the total value of the transmitted signal. Antennas are passive devices. So an antenna can have excellent gain even when the return loss stinks. For example, a parabolic antenna much larger than a wavelength might show 40 or 50 dB of (directive) gain even if it is poorly matched to a 50-ohm source. This is the consequence of all the transmitted signal being focused in a specific small solid angle. Terrible return loss (e.g. 3 dB -- half of the signal bounces back) just takes you down from e.g. 50 to 47 dBi.
Dear Anilkumar Tirunagari, can you please give the plot gain vs freq here and mention the type of antenna. Sometimes, it helps us to answer in a different way
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