High gain at lower frequencies
What are the methods for increasing the gain at lower frequencies especially in multiband patch antennas?
Urgent help needed.
Thanks in advance.
Low frequencies meaning 0-2 GHz
i am not aware of any. For a fixed physical area, you can only get a certain maximum gain.
There are "electrically short" antennas, that can be much smaller than a quarterwavelength in size. But if you try to make one, you quickly figure out that although it might have a good impedance match over your band of interest....it is very lossy, or in other words LOW gain.
Yes, I am actually getting positive gain above 2 GHz. But below 2 GHz, the gain is negative (in dB). I tried many methods, but doesn't seem to become positive for the resonant frequencies like 0.6 GHz, 0.8 GHz.
Thanks for the reply:)
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Is there any method to make the negative gain positive?
This sounds suspicious, your patch is in resonance at 0.6 GHz? Is your patch somehow electrically shorted? What substrate do you use? I think it would be helpful to show us your structure (with dimensions).
Generally, there is a limit on your efficiency (gain) and as biff44 wrote, you would need to make the antenna larger to increase the gain.
There is no real way around it, if you want more gain the antenna surface needs to increase. As frequencies drop it just gets harder to get more square wavelengths and thus higher gain.
It is like rain. If you want to catch more water you need a big bucket, not a thimble.