what is the physics or reason behind enhancing the gain by slotting the patch.
I have seen in many paper that by slotting the patch or by cutting slots in the radiating patch the gain get enhanced but what is the reason or physics behind this. How gain get enhanced by this method. what happens to the gain that it get enhanced by cutting the slot in the radiating patch. And please tell me also about what happens to current distribution? what effect it leave on current distribution?
from what i know, the slotting operation is majorly used for lowering of resonant frequency and in doing so new modes may be excited resulting into multiband nature. sometimes, the slots are specifically cut so as to bring the two obtained modes close enough to each other to result into a new hybrid mode i.e. broadband in nature.
Now, the question rises how the lowering is related to current distribution.
I shall put it in the most simplest expression i came across from the paper of XX Zang and Yang, where they say:
K.Le=pi
where k=wavenumber=2*pi/lambda
and Le=effective current path length
pi signifies the phase difference betweern the current vectors at the edge of the slot, as at the edge current can seen to be distributing into two directions.
Now as due to insertion of slot/slit, the effective current path length increases, the corresponding value of lambda increases and since lambda is inversely proportional to freq, it decreases.
one more usage of current distribution is to understand the excitation of other modes.
Moreover, coming back to your query on Gain enhancement, it is not always true, as Gain X Bandwidth product is to be constant, and due to increase in bandwidth, gain is slated to reduce comparatively in general, which can be increased by employing array technique, compromising the compactness of the antenna.
Anybody correct me wherever i am wrong. I would be happy if you point the shortcomings of my knowledge base..
hope it helps.
Thanks and regards